&EPA
United States
Environmental Protection
Agency
Total Water Management
Office of Research and Development
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EPA/600/R-12/551
July 2012
Total Water Management
By
Dan Rodrigo
COM
Los Angeles, California
Enrique J. Lopez Calva
COM
Carlsbad, California
Alek Cannan
CDM Neysadurai Technical Centre
for Integrated Water Resources and Urban Planning
Singapore
Technical Advisor
Larry Roesner
Director of Urban Water Center,
Colorado State University
Fort Collins, Colorado
Created under Contract No. GS 1OF0227J
Order No. EP09C000063
By CDM for EPA
Project Officer
Thomas P. O'Connor
Urban Watershed Management Branch
Water Supply & Water Resources Division
Edison, NJ 08837
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
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Notice
The U. S. Environmental Protection Agency ( EPA) through its Office of Research and Development (ORD)
performed and managed the research described here. It has been subjected to the Agency's peer and administrative
review and has been approved for publication as an EPA document. Any opinions expressed in this report are those
of the author and do not, necessarily, reflect the official positions and policies of the EPA. Any mention of products
or trade names does not constitute recommendation for use by the EPA.
Desktop Analysis Case Study Disclaimer
The total water management options and levels of implementation presented in this case study are for illustrative
example only, and meant to demonstrate the potential benefits using realistic water resources information for a large
urban watershed. The options presented here do not necessarily reflect actual or planned implementation by the City
of Los Angeles, nor do they reflect official policies of the City. Although the majority of data assumptions regarding
costs and benefits for these options are based on the work completed during the City's Integrated Resources Plan,
other studies and reports were utilized.
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Abstract
There is a growing need for urban water managers to take a more holistic view of their water resource systems as
population growth, urbanization, and current operations put different stresses on the environment and urban
infrastructure. Total Water Management (TWM) is an approach that examines urban water systems in a more
interconnected manner, focusing on reducing water demands, increasing water recycling and reuse, creating water
supply assets from stormwater management, matching water quality to end-use needs, and achieving environmental
goals through multi-purpose, multi-benefit infrastructure.
This study documents the benefits of TWM to water management decision-makers and can be used to support the
development of m anagement t echniques t hat could be a dopted i n order t o improve urban systems. This study
includes a comprehensive literature review that summarizes TWM p rinciples and real world applications in the
United States and abroad. The literature review was organized into different regions of the country in order to reflect
geographic water management drivers and challenges.
An evaluation protocol for analyzing TWM is presented, along with a detailed discussion of modeling techniques. A
desk top analysis was conducted to demonstrate how TWM alternatives would perform against traditional approaches
to water m anagement using a sy stems model. The model simulates supply reliability, total lifecycle costs, water
wastewater capacity, quality of receiving waters, and a number of environmental indicators. The Water Evaluation
and P lanning (WEAP) software, developed by the Stockholm E nvironment Institute, was used as the modeling
platform.
The City of Los Angeles was used as the case study for desktop analysis, using real data within a real planning
context. The City was divided into four demand areas, each with its own connections to surface water, groundwater,
and imported water supply sources, i.e., w ater from outside City limits, as well as connections to wastewater
treatment plants and receiving waters. TWM strategies that were evaluated included increased water conservation,
expanded water recycling and reuse, graywater, stormwater recharge, and rainwater harvesting. The WEAP model
simulated how integrated water supply, stormwater and water quality management can provide increased
opportunities for achieving urban system goals that would not exist in single-purpose, traditional planning.
in
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Contents
Notice ii
Abstract iii
Contents iv
List of Figures vi
List of Tables vii
Acronyms and Abbreviations viii
Acknowledgements x
Executive Summary - 1 -
Chapter 1 -1 ntroduction 1
Chapter 2 - Total Water Management Defined 2
2.1 What is Total Water Management? 2
2.2 Benefits of Whole-System Management of Water Resources 2
Chapter 3 - Total Water Management Analysis Protocol 4
3.1 Problem Definition 5
3.2 Development of Objectives and Performance Criteria 5
3.3 Characterizing Existing Conditions and Forecasting Future Conditions 6
3.4 Selecting Options and Developing Alternatives within TWM Approach 6
3.5 Development of Systems Model 8
3.6 Evaluation of TWM Alternatives 8
3.7 Selecting the Preferred Alternative (Decision-Making) 9
3.8 Defining an Implementation Strategy 9
Chapter 4 - Modeling Total Water Management 10
4.1 Modeling in a Planning Process 10
4.2 Systems Modeling in TWM 10
4.3 System Modeling Software Tools 12
4.4 Common Modeling Elements in TWM 13
Balancing Water Demands and Supplies 14
Routing and Mass Balance 14
Drinking and Receiving Water Quality 15
Costs 15
Benefits 16
Chapter 5 - Desktop Analysis Case Study: City of Los Angeles 17
5.1 Background on Case Study 17
Description of Water Resources Systems 17
IV
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Water Resource Challenges 22
5.2 Relationship between City of Los Angeles IRP and TWM Desktop Analysis 23
5.3 Model Conceptualization and TWM Options 23
TWM Options 24
5.4 Systems Model 28
WEAR Software 28
TWM Alternatives 35
Emergency and Climate Change Scenarios 36
5.5 Case Study Results 37
Water Balance and Reliability 37
Effects of TWM on Environment 41
Financial Results 46
I nfrastructure Related Benefits 47
Climate Change Scenario Results 48
Earthquake Emergency Scenario Results 50
Case Study Conclusions 51
Chapter 6 Conclusions 53
References 54
Appendix A - Cost Assumptions for Case Study A-1
Appendix B - Rainfall and Stormwater Calculations B-1
Appendix C - Hydrology and Imported Supply Assumptions C-1
Appendix D - Total Water Management Literature Review D-1
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List of Figures
Figure 1. Non-integrated water resources management vs. total water management 3
Figure 2. Total water management planning process 5
Figure 3. Building total water management alternatives 7
Figure 4. Conceptual representation of a systems model in an urban watershed (Lopez et al., 2001) 11
Figure 5. Water sectors and routing in a total water management model 13
Figure 6. Analytical layers in relation to water sectors of a typical total water management model 14
Figure 7. Water mass balance at the household level (from Mendoza-Espinoza et al. 2006) 15
Figure 8. City of Los Angeles water supply sources 18
Figure 9. City of Los Angeles Wastewater System 21
Figure 10. Demand zones for Los Angeles total water management systems model 23
Figure 11. Screen capture of WEAR interfaces 29
Figure 12. Representative schematic of demand zone 'module' in WEAR 33
Figure 13. Screen capture of the management panel for the model developed in Microsoftฎ Office Excel 35
Figure 14. Options and settings included in the baseline and total water management alternatives 36
Figure 15. Monthly water demands for San Fernando Valley zone (based on 1980-2003 Weather) 38
Figure 16. Projected total water demand for baseline and total water management alternatives 38
Figure 17. Mix of water supplies for baseline 39
Figure 18. Mix of water supplies for total water management alternative 1 40
Figure 19. Mix of Water Supplies for total water management alternative 2 40
Figure 20. Water supply deficits for baseline and total water management alternatives 41
Figure 21. Groundwater storage or total water management alternatives relative to baseline 43
Figure 22. Seasonality of zinc loading in the Los Angeles River for baseline 44
Figure 23. Comparison of annual zinc loading in Los Angeles River in 2015 for baseline and total water
management alternatives 44
Figure 24. Predicted greenhouse gas emissions over 25 years for the baseline and total water
management alternatives 45
Figure 25. Net present value cost of baseline and total water management alternatives for simulation
period 46
Figure 26. Annual operating costs of baseline and total water management alternatives 47
Figure 27. Average potential monthly wastewater flows into Hyperion Treatment Plant for baseline and total
water management alternatives 48
Figure 28. Increased Metropolitan Water District of Southern California imported water supplies in the
climate change scenario for baseline and total water management alternatives 49
Figure 29. Water supply mix and supply deficit for emergency scenario for baseline and total water
management alternatives 51
VI
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List of Tables
Table 1. Financial Measures Comparing Alternatives 46
Table 2. Comparison of Performance Measures for Baseline and Options 51
Vll
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Acronyms and Abbreviations
AFY = Acre-feet per year
AF = Acre-feet
AWWA = American Water Works Association
AwwaRF = American Water Works Association Research Foundation
BMP = Best management practice
BOD = Biochemical oxygen demand
Central = Central City (demand zone)
CSS = Combined sewer systems
CSO = Combined sewer overflows
CWA = Clean Water Act
DO = Dissolved oxygen
DWR = California Department of Water Resources
DWF = Dry weather flow
DWUR = Dry weather urban runoff
EPA = U.S. Environmental Protection Agency
ET = Evapotranspiration
GCM = Global climate model
GHG = Greenhouse gas
GPD = Gallons per day
GPY = Gallons per year
HTP = Hyperion Treatment Plant (Los Angeles)
IRP = Integrated Resources Plan (Los Angeles)
IRWMP = Integrated Regional Water Management Plans
IRWD = Irvine Ranch Water District
JPA = Joint project authority
LAA = Los Angeles Aqueduct(s)
LADWP = Los Angeles Department of Water & Power
LAGWRP = Los Angeles/Glendale Water Reclamation Plant
LID = Low impact development
MF/RO = Microfiltration/reverse osmosis
MGD = Million gallons per day
MOU = Memorandum of understanding
MWD = Metropolitan Water District of Southern California
MWDOC = Municipal Water District of Orange County
NPDES = National Pollutant Discharge Elimination System
NPS = Nonpoint source
NPV = Net present value
ORD = Office of Research and Development
O&M = Operations and maintenance
PPCPs = Pharmaceuticals and personal care products
RO = Reverse osmosis
Vlll
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SFV = San Fernando Valley (demand zone)
SP = San Pedro (demand zone)
SSO = Sanitary sewer overflows
SWP = State Water Proj ect
TITP = Terminal Island Treatment Plant (Los Angeles)
TDS = Total Dissolved Solids
TMDL = Total Maximum Daily Load
TWM = Total water management
TWRP = Tillman Water Reclamation Plant (Los Angeles)
WEAP = Water Evaluation and Planning, a systems model developed by Stockholm Environment Institute
West = Westside (demand zone)
WRP = Water reclamation plant
WWF = Wet weather flows
WWTP = Wastewater treatment plant
UPC = Uniform Plumbing Code
U.S. = United States
USDA = U.S. Department of Agriculture
UV = Ultra-violet
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Acknowledgements
An undertaking of this type requires the dedication and cooperation of a t earn. The technical direction and
coordination for this p reject w as pr ovided by the technical p reject team of the E PA, under t he d irection of M r.
Thomas P. O'Connor, the Project Officer. Dr. James Goodrich of the EPA, Dr. Charles Rowney of ACR, LLC and
Dr. Youn Sim, Watershed Management Division, Department of Public Works, the County of Los Angeles performed
reviews of this report. Mrs. Carolyn Esposito of EPA reviewed the quality assurance project plan and the report as
well.
The authors would like to acknowledge the City of Los Angeles, Department of Public Works and Department of
Water & P ower, f or 1 eadership in advancing the concepts of Total Water Management in order to address water
resources challenges for the Los Angeles urban watershed. We would also like to acknowledge Mr. Michael Schmidt
of COM for his review of the Literature Review. Special thanks go to Dr. David Purkey of Stockholm Environment
Institute in Davis, CA and Mr. Kirk Westphal of COM for their review of the systems model used in the case study
their contribution was greatly appreciated.
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Executive Summary
As population growth, urbanization and current water management operations put different stresses on the
environment and urban infrastructure, there is a need for urban water managers to take a more holistic view of their
water resource systems. In this urbanizing world, water managers need to develop new planning and management
frameworks in order for municipalities to meet challenges, such as limited fresh water sup plies, degradation of
receiving water quality, increasing regulatory requirements, flood management, aging infrastructure, rising energy
and therefore utility costs, population dynamics, and climate change. The traditional paradigm for water resources
and infrastructure management - characterized as once-pass-through use of resources, supply-side solutions to growth,
end-of-pipe solutions to waste and pollution, and single-purpose projects - is no longer adequate to meet these rapidly
evolving challenges or the long term impacts of human activity on the environment.
Traditional water resources m anagement w ill need to be transformed into a more sustainable form of urban water
management. This transformation requires new ways of thinking about urban water management and new
frameworks for planning, decision-making, design, engineering and operations. Total Water Management (TWM) is
an interconnected approach that can reduce water demands for freshwater, increase water recycling and reuse, change
stormwater m anagement into water suppl y as sets development, match water quality to end user needs and achieve
environmental goals through multi-purpose, multi-benefit infrastructure. TWM represents a new paradigm for urban
water systems. Traditional urban water management separates a municipality's water resources into distinct classes
of potable water, wastewater, and urban runoff, while TWM views all water as a resource that undergoes a continual
cycle which can be managed in a fully integrated manner.
This study was funded by the United States Environmental Protection Agency (EPA) to communicate the benefits of
TWM to water management decision-makers, municipalities, and policy decision-makers and aid in the development
and adoption of management techniques to improve urban water systems. A comprehensive literature r eview
summarizes TWM principles and applications in the U.S. and abroad. The U.S. portion of the literature review was
organized into different regions of the country in order to reflect geographic water management drivers and
challenges.
A systems model was developed and tested based on Water Evaluation and Planning (WEAP) software, an object
oriented platform in which a w ater schematic is created by using a drag and drop approach. WEAP allows users to
build a customized model of the water system, which can include water supply, distribution, treatment,
recycling/reuse, and disposal infrastructure. The software performs a mass balance throughout the system and
allocates water based on user-defined demand priorities and supply preferences. Water storage (both reservoir and
groundwater) can all be tracked over time and indoor and outdoor w ater demands can be split to account for
conservation and irrigation with recycled water, respectively. The software can simulate supply reliability, total
lifecycle costs, water quality of receiving waters, and a number of other environmental indicators.
The case study presented in this report for the TWM model i s based on the City of Los Angeles, California. Los
Angeles is one of the few cities that adopted the principles of TWM for future water resources management citywide.
In 1999, the City of Los Angeles embarked on an entirely new approach, called the Integrated Resources Plan (IRP),
for managing its water resources. The IRP took a hoi istic, watershed approach, and was a p artnership between the
different departments within Los Angeles that managed water supply, wastewater and stormwater. The goal was to
develop multi-purpose, multi-benefit strategies to address chronic droughts, achieve compliance with water quality
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laws, provide additional wastewater system capacity, increase open space, reduce energy consumption, manage
costs and improve quality of life for its citizens. This IRP was completed in 2006 and projects identified in the IRP
are planned to be implemented over the next 20 years.
Currently, 85 percent (%) of the water Los Angeles consumes is from outside the city limits. Almost 50% of the
supply is imported from the Sierra Nevada via the Los Angeles Aqueducts. The Metropolitan Water District
provides 35% of the supply, imported via the State Water Project and Colorado River. The imported water has to be
pumped hundreds of miles to reach its destination, resulting in high energy use and carbon gas emissions. The
imported water is also highly susceptible to droughts and environmental restrictions.
The current Los Angeles wastewater system consists of a large secondary treatment plant and three water
reclamation plants. By 2020, new wastewater and collection system capacity will be required. As of the completion
of the IRP, recycled water only comprised 1% of the supply.
The stormwater runoff system is separate from the wastewater system. Additionally, dry-weather runoff from
excessive irrigation water is collected and channeled untreated into receiving waters (e.g., Los Angeles River, Santa
Monica Bay and ocean). Total maximum daily loads (TMDL) for bacteria, metals and other constituents require
Los Angeles to treat or manage this urban runoff.
For this case study, Los Angeles was divided into four demand zones - each with its own connections to surface
water, local groundwater basins, and imported water sources, as well as connections to downstream wastewater
treatment plants and receiving waters. TWM strategies that were evaluated to meet projected indoor and outdoor
demands included increased water conservation, expanded recycling and reuse, graywater, groundwater recharge
and rainwater harvesting.
The model was designed to run on a monthly time step from 2008 to 2033, with a specified historical hydrologic
sequence representing 1978 to 2003. The TWM options used in the desktop analysis case study were programmed
in the WEAP model with capital, fixed operations and management (O&M) and variable O&M estimates.
Greenhouse gas emissions were based on energy requirements of different elements (e.g., water supply, treatment)
and assumptions regarding the mix of available energy sources in California. Hydrographs were used to determine
stormwater (wet weather) flows and variability, and stormwater gage data was used to determine the average dry
weather urban runoff. For the purpose of demonstrating the model, zinc was used a proxy for water quality and
TMDL compliance. Wastewater treatment and water recycling capacities were based on the IRP. Water supply
yields and cost data for TWM strategies were derived from a variety of sources including the IRP and the literature
search.
Three alternatives (or scenarios) were evaluated in the WEAP systems model: (1) baseline scenario, representing
traditional water management; (2) total water management scenario 1, focusing on increasing local water supplies;
and (3) total water management scenario 2, focusing on improving water quality. The output from the WEAP
systems model was analyzed in order to assess the relative benefits of TWM versus traditional water management
(baseline scenario).
The systems modeling of the urban water system for Los Angeles clearly shows that TWM is superior to traditional
water management. Both of the TWM scenarios had greater benefits at lower costs when compared to the baseline
scenario approach. This is mainly a result of the high cost for imported water, which is also very vulnerable to
droughts. Additional analysis of effects of climate change and damage to water systems due to earthquake
reinforced the benefits of the TWM scenarios versus the traditional baseline approach.
The WEAP model demonstrated how TWM approaches would perform against traditional water management
approaches. The results presented in this case study are an example that can be used by other municipalities. TWM
does not necessarily need to be limited to water supply analysis alone as in other areas of the country it may produce
benefits for water quality and flood management. By examining water resources in a more interconnected and
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integrated manner, TWM allows water managers to explore multi-purpose projects and determine whether or not it
makes economic sense to move forward with TWM. Each application of TWM needs to be evaluated based on local
water resources challenges and unique baseline conditions. Decision support tools such as WEAP and other system
simulation models can be useful in analyzing whether TWM produces net benefits.
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Chapter 1 - Introduction
In order for municipalities to meet challenges such as limited fresh water supplies, degradation of receiving water
quality, i ncreasing r egulatory r equirements, flood m anagement, aging infrastructure, and rising utility costs, new
planning and management frameworks must be developed for urban areas. The traditional approach for managing
water resources and infrastructure is no longer adequate to meet these rapidly evolving challenges or the long term
impacts of human activity on the environment.
Traditional water resources management characterized as "once-pass-through" use of resources; supply-side
solutions to growth; "end-of-pipe" solutions to waste and pollution; and single-purpose projects will need to be
transformed into a more sustainable, holistic approach. This transformation will require a new paradigm for water
resources management and new frameworks for planning, decision-making, design, engineering, and operations.
Total Water Management (TWM) is an approach based on a holistic v iew of the water resources sy stem and
principles of sustainability. TWM can be utilized to increase water resources efficiency and enhance overall benefits.
It examines urban water systems in a more interconnected manner, focusing on reducing water demands for fresh
water, increasing water recycling and reuse, creating water supply assets from stormwater, matching water quality to
end-use needs, and achieving environmental and societal goals through multi-purpose, multi-benefit solutions. While
traditional urban water m anagement separates a city's water resources into the three distinct classes of water, i.e.,
potable, wastewater, and stormwater, the TWM approach views all water as a resource that undergoes a cycle that can
be managed in a fully integrated manner.
Objective
This study introduces TWM as an approach to plan and manage water systems in an urban watershed, and to illustrate
and communicate the potential benefits of TWM to utility managers, municipalities, policy decision-makers and
practitioners. The first element of the study was a comprehensive literature review that summarized TWM strategies
being implemented in the United States and internationally. The second element was development of a standardized
analytic approach that can be used to guide those wishing to implement TWM. T he third element w as the
development of a desktop analysis to demonstrate how two TWM alternatives would perform against the traditional
approach to water management, using the City of Los Angeles as a case study.
Report Organization
The main report is divided into five chapters: (1) Introduction; (2) Total Water Management Defined; (3) Total Water
Management Evaluation Protocol; (4) Modeling Total Water Management; (5) Desktop Analysis Case Study; and (6)
Conclusions. Technical assumptions for the Case Study are presented in Appendices A through C. The literature
review of Total Water Management strategies is presented in Appendix D
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Chapter 2 - Total Water Management Defined
2.1 What is Total Water Management?
TWM presents a new paradigm for urban water systems. It is an approach that seeks better management
and efficiency of water resources, and breaks down institutional barriers that separate water into the silos
of drinking, wastewater, and stormwater. TWM analyzes the entire water cycle to develop sustainable
water supplies, improve water quality, and reduce impacts of stormwater in a cost-effective manner.
Through the process of TWM, wastewater and stormwater become water supply assets to meet water
demands based on end user needs, and land uses are analyzed to reduce impermeable surfaces to allow
water to be retained onsite.
The American Water Works Association Research Foundation (AwwaRF) (1996) defines TWM as: "The
exercise of stewardship of water resources for the greatest good of society and the environment." This
definition of TWM is very broad and related to concepts such as Integrated Resources Planning
(AwwaRF, 1998) and Integrated Water Resources Management (Grigg, 1996). Common to all of these
concepts is the integration across water sectors and geopolitical boundaries. Most practically, the term
TWM has been applied to planning and projects with an emphasis on multi-purpose, multi-beneficial
solutions to solving water resources problems. A variety of TWM projects with a central objective on
water supply are described in Hill et al. (2007), Baldwin et al. (2007), and Muniz et al. (1993).
2.2 Benefits of Whole-System Management of Water Resources
In TWM we seek solutions that meet both community and environmental needs. Grigg (2008) mentions
that TWM "is about the balance between our responsibilities to provide safe and reliable water services
and to protect the environment." Young (2006) proposes that TWM is driven by four principles: (1)
recognizing freshwater as a finite but renewable resource; (2) managing water resources on the basis of
watersheds and involving relevant stakeholders; (3) preserving water resources, and (4) allocating water
equitably. The concepts of renewable resource, watersheds, stakeholders and equitable allocation can all
be implemented in a TWM approach that uses the watershed as a unit of analysis, and that evaluates water
in its entire cycle.
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Non-Integrated Water Resource Management
Receiving
Waters
wef
weather
Total Water Management (Integrated Water Resources)
Beneficial reuse ofstormwater
(e.g., groundwater recharge)
Reuse of treated
wastewater
wet
weather
Figure 1. Non-integrated water resources management vs. total water management
Figure 1 i llustrates the difference between non-integrated water resources management and TWM. In this figure,
receiving waters represents surface and groundwater sources while dry-weather stormwater represents non-peak storm
events or low flows that occur from over irrigation in urbanized watersheds. In some locations of the U.S., these dry-
weather stormwater flows are conveyed to the wastewater system for treatment and discharge. In the non-integrated
approach, urban watersheds use more receiving waters for their water supply, and heavily discharge wastewater and
stormwater into receiving waters. This approach can result in detrimental environmental impacts, as well as lead to
inefficiencies in the u se o f w ater. TWM s ignificantly improves the opportunities to obtain benefits from water,
regardless of its stage in the water cycle. Water conservation reduces the demand for fresh water. Rather than
stormwater being viewed as a nuisancesomething to get rid of as soon as it starts flowing in order to avoid
floodingit should be an asset, where it can be allowed to recharge groundwater through best management practices
(BMPs) such as swales and use of porous pavement, or directly captured using cisterns. Furthermore, wastewater can
be recycled, providing both environmental and dependable water supply benefits. The end result of TWM is reduced
discharges to receiving waters and reduced reliance on natural surface and groundwater supp lies to meet water
demands.
Typically, TWM strategies include:
Water conservation
Reuse of wastewater
Reuse of graywater
Stormwater best management practices (BMPs)
Rainwater harvesting
Dry weather urban runoff treatment plants
Dual plumbing for potable & non-potable uses
Separate distribution systems for fire protection
Multi-purpose infrastructure
Using the right water quality for intended use
Green roofs
Low impact development (LID)
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Chapter 3 - Total Water Management Analysis Protocol
The purpose of this chapter is to give water resource practitioners guidance on how to analyze TWM, and outline the
major steps and elements of the planning process. Evaluating TWM follows many of the same principles of traditional
planning.
Generally, the TWM planning process includes the following general steps:
Define study area and problem
Define planning objectives and develop performance criteria
Characterize existing conditions and project future scenarios
Identify and characterize individual TWM options
Combine TWM options into complete alternatives or portfolios
Develop systems model approach and select appropriate analysis tools
Evaluate TWM alternatives
Select preferred TWM alternative
Develop implementation strategy, addressing risk and uncertainty through adaptive management
Not all of these steps are chronological or applied in series. The different planning steps can be performed as three
parallel paths at the beginning of a project converging on the analysis and decision making as illustrated in Figure 2.
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Analyze TWM Alternatives
(using systems analysis tools such as simulation models)
Define Implementation Strategy
Figure 2. Total water management planning process
3.1 Problem Definition
The first step in the process is to define the problem and the drivers for the project. Is the project driven by demand
growth? Is there a supply reliability problem? Is it driven by regulatory compliance on water quality? Is it a strategic
first step to define capital investments? The problem definition helps to guide the entire planning process. This step
is can be done with utility officials or with stakeholders in a facilitated workshop. Often, a mission statement for the
project is developed during this step.
This step is also where major issues and stakeholders are identified. Is there an established group of stakeholders that
collaborates with the utility or city? Are there contentious issues or antagonistic relationships with some members of
the public? D o w e have s ufficient technical knowledge about the engineering i ssues? Is there significant lack o f
relevant data? These t ype of situational analysis questions help define the TWM process in its technical and
stakeholder dimensions.
3.2 Development of Objectives and Performance Criteria
Before identifying and analyzing any solution, project or strategy, planning objectives need to be clearly defined.
Objectives set out to answer the questions: "what are we trying to achieve?" or "why are we preparing this plan?"
Objectives define the broad goals of the program, in easy to understand statements. And while it is not essential, it is
recommended that objectives should be defined in a collaborative setting with public stakeholders and utility officials.
A TWM overall goal i s achi eved when achieving individual objectives simultaneously by implementing T WM
strategies.
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Examples of TWM individual objectives may include:
Ensuring water supply reliability under all hydrologic events
Improving drinking water quality
Managing utility costs
Providing adequate wastewater system capacity
Reducing impacts of stormwater on the environment
Increasing water use efficiency
When a TWM strategy is successful, these sample objectives listed above can be achieved simultaneously, to different
degrees. This contrasts significantly with traditional water planning where a single objective may be pursued, such as
improving water reliability at the minimum cost. For each objective, performance metrics need to be developed in
order to quantify how well alternatives achieve the desired goals. Examples of performance metrics include:
Frequency and magnitude of water shortages
Amount of arsenic in drinking water
Total lifecycle costs
Bacteria count in receiving waters
These p erformance m etrics ne ed to be specifically mapped to all of the objectives. A g ood de scription ofcriteria
development is presented by Michaud (2009) explaining not only the process to develop criteria but the attributes that
criteria need to have to be effective in discriminating among alternatives.
3.3 Characterizing Existing Conditions and Forecasting Future Conditions
Characterizing the existing conditions and forecasting future conditions establishes the baseline for the project. This
characterization will need to answer the following questions: What are the existing water supplies? Will these
existing water supp lies decrease overtime? What are the current or expected water quality and environmental
regulations? What is the current i nfrastructure for water, wastewater and stormwater? What are the current and
projected water demands?
In many cases, this baseline condition can be e stablished w ith information from recently completed utility m aster
plans for water and wastewater. This is also sometimes referred to as a "no project" or "no action" alternative.
3.4 Selecting Options and Developing Alternatives within TWM Approach
The term "option" refers to individual projects or p rograms for each of the historically individual sectors of water:
drinking water; wastewater; and stormwater. Identifying and characterizing these options is a very important step in
the TWM process. For each option, it is important to identify the benefits provided and full costs.
Because no one option will likely solve all of the water resources goals identified, options must be combined to form
complete alternatives or portfolios. This is especially true in TWM, where goals are to be met for multiple water
sectors. The creation of alternatives is an important step because evaluation criteria are applied at the alternatives
level and not individual project level. The reason for this is simple; any one specific project may not perform well by
itself, but when combined with another option or several options, the entire alternative may perform well due to the
synergistic nature of TWM.
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Given the num her of pot ential options spread across three utility sectors, i.e., drinking water, wastewater and
stormwater, the number different permutations or combinations will result in dozens of alternatives to evaluate. To
keep the number of alternatives manageable, the planning objectives can be used to develop alternatives centered
around "themes." Example alternatives based on themes could include:
Balanced impacts
Balanced benefits
Low cost alternative
Low risk alternative
High reliability alternative
High sustainability alternative
Alternative with high adaptability to regulatory, technology and market changes
Using t hemes ar e an effective way to keep the num ber of initial alternatives manageable. Once these initial
alternatives are evaluated, hy brid alternatives can be constructed by t aking the best elements from the initial
alternatives in order to create "super performing" alternatives. Figure 3 depicts how alternatives are developed from
individual options.
Objectives
Performance
Measures
TWM
Options
TWM
Alternatives
Defining performance measures for each objective
-> Combining options into alternatives
-> Measuring alternatives against objectives
Figure 3. Building total water management alternatives
7
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The alternative definition step may be one of the most valuable in a TWM process. Creativity and expertise, as well
as knowledge of the system and the issues, are necessary to define innovative solutions. This step in a TWM process,
where options are combined into alternatives, traditionally requires an internal workshop with experts and members of
the team with significant knowledge of the system.
3.5 Development of Systems Model
A systems model adds significant value in evaluating the alternatives against the objectives and performance criteria.
Chapter 4 explains the significant advantages in developing a sy stems model as a cen tral analytical tool in TWM
planning. The first important step of developing a systems model is defining the 'modeling' objectives which will
define how the model can help inform the problem statement and meet the planning goals.
A second step in developing the systems model is the definition of its scope, which as the following dimensions:
Geographic space (city, county, urban watershed)
Sectors (water, wastewater, stormwater)
Analysis layers (cost, water quality, environmental impacts, etc.)
Time scale (annual, monthly, daily)
In every modeling effort, it is critical to write a modeling plan describing the modeling objectives and the scope, as
well as important characteristics of the system. When the modeling plan is complete, the selection of the tool can take
place. Chapter 4 includes a more detailed discussion on modeling TWM and the tools that are available.
Before programming the model begins, a conceptualized model of the system needs to be constructed, i.e., drawn in
one or sev eral sch ematics. The cone eptual m odel ne eds t o include al 1 r elevant model ( system) elements an d
relationships. After the conceptual m odel is d eveloped, the p rogramming t ask can take place. It is important to
recognize that the development of the conceptual model will be an ongoing task until the programming is finished due
to the fact that the programming task results on a better and deeper understanding of the system.
After the programming takes place and the model is complete, it needs to be tested and validated. Several checks
need to take place during and after model programming, and the model needs to be validated with the simulation of
existing conditions. Validation includes tests to see if mass is conserved, meaning all sources of water are tracked
from when it enters to when it leaves the system. Validation is also important to make sure all units are converted
properly and that all cost calculations are tested. I n more complex models, validation can be used to test how the
model simulates water storage operations for a past hydrologic condition.
3.6 Evaluation of TWM Alternatives
After the systems model i s programmed and validated, the evaluation of the alternatives can take place. This step
involves the quantitative analysis of how each alternative performs against the performance measures. It is important
in this step to clearly define how the performance measures will be reported. W ill the performance be measured
cumulatively over the planning horizon (e.g., build-out conditions), or for a specific design year? It is also important
to determine whether results will be presented as a probability distribution or as a point estimate. Many of the system
model softwares allow for runs of Monte Carlo simulations. In Monte Carlo simulations, random draws are made for
key decision variables (e.g., hydrologic years, variability in operations and maintenance (O&M) costs, etc.) and the
model output can then be presented as a histogram or exceedance probability plot. A score card of alternatives and
their performance is another way in which output from this step can be displayed.
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3.7 Selecting the Preferred Alternative (Decision-Making)
After the analytical phase of the project, the technical team needs to synthesize the great amount of information that is
generated as part of the analysis. Because there will likely be many performance measures that are reported from the
systems model and these measures will all be reported in different units, i.e., flows in million gallons per day (MOD),
or costs in dollars per year, the use of a multi-criteria decision tool is often used to standardize the output and rank
alternatives. The use of such a tool will clearly show tradeoffs between the alternatives and help decision-makers in
selecting a preferred alternative.
3.8 Defining an Implementation Strategy
The decision-making step usually results in the selection of one alternative or a short-list of alternatives. TWM plans
can formally addr ess unc ertainties and risk assoc iated with the forecasting st ep using a daptive m anagement t o
develop an implementation strategy. For example, if there are several variables that are highly uncertain, such as
demand forecast or regulatory requirements, the systems model can be used to develop separate implementation paths
associated with different scenarios of the future. Trigger points can be established in the future, and when a specific
path is becoming more apparent, then the implementation strategy can be adjusted accordingly.
Because TWM by its very nature explores all water sectors, implementation of TWM projects will require greater
coordination between those who manage water, wastewater and stormwater. In some cases, two or even all three of
these water sectors are managed by a single city agency, such as public works, and this will make the implementation
of TWM more straight forward. But more commonly (and especially in larger cities), there are three separate utilities
or city agencies that manage water resources. In this case, implementation of TWM projects will require some
institutional barriers to be eliminated and greater cooperation between utilities.
Implementation of TWM projects will likely involve different ways to finance and fund capital infrastructure between
multiple partners, as well as agreements on how facilities will be operated once constructed. These agreements can be
in the form of a memorandum of understanding (MOU), through an oversight entity such as the mayor's office, or
through a joint project authority (JPA).
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Chapter 4 - Modeling Total Water Management
4.1 Modeling in a Planning Process
Any planning process involves the systematic evaluation of alternatives in order to make a rational decision, given
baseline and projected data. McAllister (1995) de scribes environmental planning as a process encompassing five
steps: "(1) identify the problemto be addressed; (2) design alternative solutions to the problem; (3)evaluate the
alternatives; (4) decide on the action to be taken through the appropriate political process and implement it; and (5)
monitor the results." The third step, the evaluation step, is an analytical step and usually is highly quantitative in
nature. The quantitative analysis of alternatives can be performed with a range of analytical tools. Selecting which
tool to use should be based on the complexity of the problem and what is at stake in the decision making process.
Computer models are common analytical tools used to understand and simulate water resources and environmental
systems in which the alternatives are applied. The evaluation and quantification of the response of those systems to a
set of management and planning decisions (alternatives) is adequately performed with models. Models can optimize
or simulate a system, and quantify the water resource and environmental system variables over time. Models can give
decision makers the information needed for Step 4 of the planning process in McAllister's description of the planning
process.
In traditional planning, usually one flow model i s used for each stage of the water cycle. For example, hydraulic
model for drinking water; collection system model for wastewater; and hydrology model for stormwater. In addition,
treatment and/or water quality models may also be necessary. But in TWM when all water resources are modeled as
an interconnected system, more closely mimicking the real watershed, then a different type of model is required. A
"systems" model, as it is commonly called, is ah igher-level model that simultaneously simulates the entire water
cycle. This systems model does not replace more detailed models for water supply, wastewater, or stormwater, but in
fact is used in conjunction with these detailed models.
4.2 Systems Modeling in TWM
The concept of TWM requires a systemic view of an urban watershed. In TWM, water at different stages of the water
cycle is not seen as independent "types" of water such as raw water, potable water, wastewater and runoff but rather
as a resource that undergoes a cycle which can be managed holistically. Pollutants are not seen as specific attributes
i.e., sometimes assumed to be inherent, of a "type" of water. Instead, pollutants are seen as elements that the water
will transport once introduced into the water cycle at specific locations and as a result of specific human activities and
practices and natural processes. In TWM, managers track where pollutants are introduced in the water cycle and how
they are transformed and removed from it. Pollutants are not just tracked within a sector of the system, i.e., potable
water, wastewater, and stormwater, but also as they move between sectors. TWM describes the pollutant's ultimate
fate and how managing decisions can impact that fate and transport.
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Systems models are well suited as analytical tools for TWM. The term "systems model" is used to define a model
that i ncludes t he r epresentation o f di fferent c omponents of a n overall s ystem. A sy stems model of an urban
watershed cou Id include a representation of the w ater de mands, water s ources, water t ransmission and treatment,
wastewater co llection and t reatment, wastewater an d stormwater d ischarges, and receiving waters. It could also
include economic variables and environmental impacts. A systems model differs from the "model of a system" (e.g.,
a groundwater model, a wastewater treatment plant (WWTP) process model, or a water distribution network model)
in that, in modeling the urban watershed, the systems model places emphasis on the interrelationships between the
components o f t he ov erall sy stem. The sy stems model o f a n u rban w atershed w ould pi ace an e mphasis on t he
interrelationships between: indoor water demands and household wastewater generation; wastewater recycling and
irrigation water demands; surface runoff and groundwater recharge; and stormwater and water quality in receiving
waters.
Systems models are dynamic models. These models simulate variables overtime to allow decision-makers to test
how alternatives change the system, and also to test "what-if' scenarios of different possible future conditions. A
systems model can estimate specific benefits from water management decisions that can impact more than one sector
in the watershed (e.g., water supply and water quality in receiving waters). In the context of TWM, a systems model
can also be used to measure the economic, environmental and social elements of sustainability. Figure 4 presents a
schematic representation of a systems model of an urban watershed.
Sources
Imported
Water
Collection and
Conveyance
Treatment
Conservation
Disposal
Environmental
Use
Receiving
Waters
Descentralized
Capture and Use
End of System
Capture and Use
Dry Weather
Discharge
Dry Weather
Urban Runoff
Conveyance
Dry Weather
Urban Runoff
Treatment
Figure 4. Conceptual representation of a systems model in an urban watershed (Lopez et al., 2001)
The use of a systems model can help formalize the relationships, i.e., establishing actual equations representing the
relationships and quantifying the effects of management options on a specific area of the system. The main advantage
of a systems model is that it can keep track of a number of simple relationships and generate one comprehensive list
of outputs relevant for managers, enabling them to keep track of all of the system responses, costs and benefits. For
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example, the systems model would quantify the impact indoor water conservation will have on water demand and
wastewater discharges. Additionally, conservation will come at a ce rtain cost of implementation, but can represent
savings on water and wastewater infrastructure. The overall energy requirements to operate the system will also vary
with the conservation strategy. One management decision can trigger responses in several variables of interest and
when the number of decisions and system components grows, a system model for TWM becomes crucial.
Systems models can be constructed to simulate the variability in hydrology, or any other variable that has volatility or
a probabilistic nature, overtime and are ableto simulate the response of a system over different time scales. A
systems model can simulate a system under normal hydrology conditions, droughts and wet periods as well.
4.3 System Modeling Software Tools
Many s imulation t ools a re av ailable t hat cou Id be used for a T WM study. Common s ystems modeling s oftware
include:
STELLA - http://www.iseesystems.com/softwares/Education/StellaSoftware.aspx
PowerSim - http://www.powersim.com
Vensim - http://www.vensim.com
ExtendSim - http://www.extendsim.com
GoldSim - http://www.goldsim.com
These "g eneric" si mulation tools allow us ers to build a customized model of any kind of s ystem (e.g., bus iness
system, ecosystem, natural or physical system, or water system). These models can be simple, one-sector systems, or
highly complex, interconnected systems. What makes these tools so powerful is the ability to see dynamically how a
system r esponds to external f orces or actions, i.e., strategies. The m odels a re built using ob ject-oriented
programming, show results visually through interactive graphics, and are very transparent. They also have the ability
to run Monte Carlo simulations, enabling probabilistic analysis to be conducted. Because these models are generic in
nature, they are well suited for water resources system evaluations.
In their application for TWM, the system models perform a mass balance throughout the system and allocate water
based on user-defined demand priorities and supply preferences. In these models, important system pe rformance
measures can be defined and tracked - including supply reliability, cost, water quality, storage (surface and
groundwater), return flows, stream flows and impacts to the environment. However, these models require the entire
system to be constructed from scratch, and the user must be careful in explicitly defining the units of measurements
and formulas for all conversions. Therefore, these models are to be used by experienced practitioners in the fields of
systems modeling and engineering.
The software WEAP (http://www.weap21 .org). developed by the Stockholm Environment Institute, is a systems
model created specifically for water resources planning. Unlike the generic systems models described above, WEAP
has built-in water r esources e lements and does all unit conv ersions automatically. WEAP can ev aluate r unoff,
groundwater/surface interactions, water conservation, water quality and storage. It is more suited for planners, and
models can be constructed more quickly than the g eneric sy stem models d escribed above. However, W EAP ha s
limited output and certain important performance measures would need to be evaluated outside of the model, using a
spreadsheet or some other means. WEAP is also not able to directly run Monte Carlo analysis. So if the nature of the
problem is highly variable or uncertain, other systems models may be more appropriate.
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For this study WE AP was selected to analyze TWM for the case study pre sented in Chapter 5. The decision was
based on the ease of use and quickness in developing the model, and the fact that WEAP is commonly used all across
the globe for similar integrated water resources planning.
4.4 Common Modeling Elements in TWM
TWM models i ncorporate el ements i n two dimensions: ( 1) t he di fferent w ater se ctors, such as d rinking w ater,
wastewater, or st ormwater; a nd (2) the a nalytical 1 ayers, such as supply r eliability, cost, water qu ality, and
environmental impacts.
Included in the water sectors is the demand for water, and how water moves through the urban watershed cycle, i.e.,
sources of water supply, drinking water distribution and treatment, wastewater collection and treatment, stormwater
flows and system, and disposal of wastewater and stormwater to receiving waters. Figure 5 s hows an example of
water sectors in an urban watershed and how they are interconnected. Figure 5 is one conceptualization of a water
system out of many that can take place in a TWM project, depending on the case-by-case emphasis of the different
elements oft he system (e.g., groundwatervs. wastewater). Butall TWM conceptualizations need to include the
interrelationship between the systems and treat water, regardless of its stage in the water cycle, as a traceable entity
with conservation of mass.
In addition to the water sectors, a TWM model can contain additional analytical layers for all of the performance
metrics that are important to decision makers, i.e., costs, supply reliability, greenhouse gas (GHG) emissions, water
quality, and environmental impacts. Figure 6 provides a schematic of analytical layers in relation to water elements.
Rainwater
Pumping Storage
Pumping Treatment Storage
___>
infiltration
Demands
Indoor Potable
Indoor Non-potable
Cooling
Irrigation
Municipal WTP
Figure 5. Water sectors and routing in a total water management model
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Figure 6. Analytical layers in relation to water sectors of a typical total water management model
Balancing Water Demands and Supplies
An important aspect of a TWM model is the balance between water demands and supplies in the system. Demands
need to be differentiated according to the quality of water required, as well as the timing and seasonality of demand.
Geographic location of t he de mands may a Iso be i mportant, de pending on t he c omplexity of t he w atershed a nd
limitations of water supply. In most cases, separation of indoor and outdoor water demands will be important in order
to evaluate the potential for water conservation, recycled water, graywater and other alternatives that are targeted for
non-potable demand.
The sup ply si de in the TWM model needs to incorporate all the different sources of water, including safe yield,
annual and monthly hydrologic variation, and long-term sustainability. Operational assumptions, especially as they
relate to storage, are also very important to explicitly define. For example, a water supply source may be more than
adequate to meet average annual water demands, but the capacity of conveyance and/or treatment facilities may not
be sufficient to meet peak-day demands. Thus, the TWM must be able to measure operational constraints as well as
supply availability.
Routing and Mass Balance
In a T WM model, the flow paths oft he volume of water in each water sector should be tracked rigorously. For
example, potable water enters a building and it is used; some of it is consumed and some is discharged as wastewater.
The consumption path and the discharge path are tracked in TWM models to conserve mass. Depending on t he
supply options evaluated in a TWM model, the paths can be simplified or can multiply elevating the complexity of the
system. Figure 7 shows an example of tracking of flows within buildings with and without graywater systems.
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Figure 7. Water mass balance at the household level (from Mendoza-Espinoza et al. 2006)
Mass ba lance in aTWMmodel is fundamental. The software t ools de scribed earlier h ave di fferent degrees of
rigorousness regarding conservation of mass. In some cases, the tool requires the analyst to program mechanism to
enforce mass balance and in some cases, as in the case of WEAP, mass balance is enforced by the program.
Drinking and Receiving Water Quality
In a TWM study, water quality is an essential element that is of interest to decision makers. Water quality can be
tracked for drinking water or receiving waters, or both. TWM models use the same mass balance routines to estimate
water qua lity constituents. However, TWM sy stem models g enerally don' t include sophisticated k inetics.
Temperature and residence times of appropriate scale are two variables commonly absent in TWM models and thus
the quality elements are limited to simplified mass balance and fate and transport. TWM models can include some
decay or uptake processes but they will be modeled with simplifying assumptions due to the time scale relevant to
TWM, i.e., years, months and, rarely, days. All of the simulation tools mentioned as appropriate for TWM have the
ability to accept data from other models (with varying degrees of user-friendliness), and all of the models can include
transform functions that are derived from traditional water quality models.
Costs
Cost is a layer of analysis always present in TWM models and studies. Given that most TWM models will have the
abilityto simulate the system and quantify the actual use of each water source per unittime (e.g., monthly), it is
appropriate to separate v ariable costs from fixed cos ts in addition to having capital costs included in the model.
Variable costs, when tracked and accounted appropriately, can make a difference to decision makers when deciding
on planning alternatives.
Costs in TWM need to include the operation and maintenance costs of programs and not only capital projects. For
example, w ater c onservation us ually doe s no t i nvolve i nfrastructure p rejects, but i ts c ost t o the u tility or c ity
implementing the program need to be accounted for nonetheless. Costs of compliance with regulations also need to
be included. Some costs can be accounted for as benefits if they are considered avoided costs.
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Benefits
The step of the planning process when decision makers select a specific alternative is not the analysis step but rather a
synthesis step where a method to interpret the information from the systems model is used to compare alternatives.
Conceivably, any TWM process could include a "cost-benefit" comparison in the traditional sense where all benefits
are monetized. In most cases, however, benefits in TWM are not aggregated into one monetized metric. Rather
TWM studies compare alternatives from a multiple-objective perspective.
In that sense, benefits can be associated to the degree to which the alternatives meet different objectives. If a TWM
study i ncludes objectives on e nvironmental pr otection, c ompliance w ith r egulations, a daptability of the pi an, o r
environmental justice, t hen be nefits c an be m easured qua litatively or qua ntitatively i n t erms of how well e ach
alternative meets the objectives. Output from the TWM model, usually in terms of unit flows from different sources
of sup ply, can be used to measure these be nefits. For ex ample, based on un it f lows of di fferent supply sources,
energy consumption can be derived, and from this energy consumption GHG emissions can be estimated.
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Chapter 5 - Desktop Analysis Case Study: City of Los Angeles
5.1 Background on Case Study
In 1999, t he City of Los Angeles (City) embarked on an entirely new approach for managing its water resources,
called the Integrated Resources Plan (IRP) (City of Los Angeles 2006a, 2006b and 2006c). The IRP took a holistic,
watershed app roach and was a partnership between the different departments within the City that managed water
supply, wastewater, and stormwater. Prior to the IRP, the three departments that managed the City's water resources
rarely coordinated or looked at their respective systems as part of a bigger whole. The goal of the IRP was to develop
multi-purpose, m ulti-benefit st rategies to address chron ic droughts, a chieve c ompliance w ith w ater qua lity
regulations, provide additional wastewater system capacity, increase open space, reduce energy consumption, manage
costs, and improve quality of life for its citizens. The IRP was completed in 2006, winning numerous state and
national awards, and well supported by the City's diverse stakeholders. The projects identified in the IRP preferred
strategies will be implemented over t he cou rse of the ne xt 20 years, including i ncreased use o f recycled water,
beneficial use of stormwater, increased water conservation, and multi-purpose/multi-benefit infrastructure.
Description of Water Resources Systems
The C ity and surrounding urba n watershed is g eographically di verse and 1 arge. 11 st retches from t he vast S an
Fernando Valley, a large downtown and central city area, the west side beach areas, and a port area in the southern
part of the City. Running throughout the City is the Los Angeles River, now mostly a concrete channel designed for
flood management. The urban watershed also has several groundwater basins located within the City or adjacent to
the City. The City's water resources systems are composed of drinking water, wastewater, and stormwater. Each of
these sy stems i s b riefly de scribed to provide a b asic unde rstanding of the issues and challenges facing this urban
watershed. The cited sources for these system descriptions come from the Los Angeles Department of Water &
Power (LADWP) Urban Water Management Plan (LADWP, 2005) and the Los Angeles Integrated Resources Plan
(City of Los Angeles 2006a, 2006b and 2006c).
Water
The C ity r elies primarily on three w ater supply sour ces: (1) t he L os A ngeles A queducts ( LAA); (2) 1 ocal
groundwater; and (3) supplemental w ater pu rchased from t he M etropolitan Water D istrict of S outhern C alifornia
(MWD). See Figure 8 for a m ap and historical reliance on these water supply sources. Historically, these water
sources have delivered an adequate water supply to meetthe City's needs. Currently, the City relies on imported
water, water from outside City limits, for 85 percent (%) of its water demands. Almost 50% of the supply is imported
from the Sierra Nevada via the LAA. The MWD provides 35% of the City's supply, imported via the State Water
Project (SWP) and Colorado River. The imported water has to be pumped hundreds of miles to reach its destination,
resulting in high energy use and carbon gas emissions. The imported water is also highly susceptible to droughts and
environmental restrictions. Approximately 15% of the City's water supply is pumped from local groundwater.
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Recycled
MWD Water
(SWP&CRA) -1%
35%.
Local
Groundwater
15%
Los Angeles
Aqueducts
Local Groundwater
Los Angeles
Los
Angeles
Aqueducts
49%
Colorado River |
Aqueduct
Figure 8. City of Los Angeles water supply sources
The City has been a national leader in implementing water conservation. Since 1991, LADWP has installed over one
million ultra-low-flush t oilets, hu ndreds o f thousands of 1 ow-flow s howerheads, a nd p rovided r ebates f or hi gh
efficiency clothes washer machines and smart irrigation devices. In fact, the City uses less water now than it did in
1990, despite adding over 700,000 new residents to its service area.
Los Angeles Aqueducts
Supplying almost 50% of the City's water supply, the LAA delivers water via gravity alone from the Mono Basin
region in the eastern Sierra Nevada extending approximately 340 miles south. The First Los Angeles aqueduct was
completed in 1913. To meet the growing needs of its population, the City completed construction of the Second LAA
in 1970. Seven reservoirs on the system have at otal combined reservoir capacity of the system is approximately
300,560 acre-feet (AF). D eliveries since 198 9 from the LAA have averaged approximately 275,000 a cre-feet/year
(AFY) compared to a total annual demand around 650,000 AFY. Of the three supply sources for the City, the LAA
supplies the highest quality water.
Surface runoff from snowmelt in the eastern Sierra Nevada feeds the LAA system. Runoff peaks in the late spring
and s ummer pr oviding flexibility i n ope rating t he L AA sy stem and the w ater sy stem as a w hole. However, t his
supply source is subject to substantial variability due to hydrologic variability in the eastern Sierra Nevada with wet
and dry years. Annual system deliveries are dependent upon annual snowfall in the eastern Sierra Nevada. Years
with higher snowpack levels typically result in larger volumes of imported water delivered to the City.
Since the late 1980 's environmental issues have required the City to use an increasingly significant volume of its
LAA supplies for environmental mitigation in the Owens Valley and Mono Basin regions. As of 2005, the City has
committed approximately 166,000 A FY or approximately 40 % of its historic LAA water supply to environmental
enhancements in these regions. To offset the supply reduction, the City has developed other resource management
opportunities to maintain a reliable water supply system.
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Local Groundwater
Local groundwater provides approximately 15% of the total water supply, increasing up to 30% of the total water
supply during droughts. The City has water rights in five groundwater basins. Approximately 86 % of the City's
groundwater supply, on average, ispumped from the UpperLos Angeles River A rea g roundwater basins, the San
Fernando, Sylmar, and Eagle Rock groundwater basins. The Central Basin supplies the remaining 14% of the City's
groundwater supply. Groundwater rights in the West Coast Basin are not utilized as a result of localized water quality
issues. All o f t he b asins ar e adjudicated, i.e., water rights for specific users ha ve be en es tablished, and are
administered by an administrative entity with jurisdiction over a specific basin called Watermaster.
The S an F ernando B asin i s t he C ity's pr imary groundwater s ource s upplying a pproximately 80 % of the to tal
groundwater supply. In accordance with the adjudication the City has the right to the native safe yield of 43,660 AFY
and t he r eturn of imported w ater of a pproximately 43,000 A FY pr oviding ana nnual t otal e ntitlement of
approximately 87,000 AFY. The adjudication allows the City to store water in the basin to supplement the annual
SFB ent itlement. In 2005 t he s tored w ater c redit w as a pproximately 320,000 A F. The pra ctice o f r echarge and
extraction known as conjunctive use in the basin is practiced by pumping the annual entitlement generally between
April through O ctober, t he hi ghest w ater de mand m onths, a nd r elying on more r eadily a vailable i mported w ater
during the lower demand months, November through March. Captured stormwater and/or imported water are used to
recharge the basin. Average annual recharge through spreading basins is approximately 25,390 AFY.
Metropolitan Water District
Approximately 35% of the City's water supply is provided by MWD. Supplies are purchased by the City from MWD
to use as a supplemental supply to make-up any deficits between the City's water supplies and customer demands. As
the largest water wholesaler in California for domestic and municipal water use, MWD obtains its supplies from the
SWP as a contractor, its ownership of the Colorado River Aqueduct, and from storage and water transfer programs.
The City is one of MWD's 26 member agencies.
MWD is the largest contractor of the SWP, with a contract for 2.01 million AFY of the project's capacity of 4 .23
million AFY. SWP water is pumped from the Sacramento-San Joaquin River Delta (Delta) in Northern California
and delivered via aqueducts to Southern California. Environmental issues and variable hydrology dramatically reduce
actual deliveries from the SWP. MWD's goal is to receive 650,000 AFY during drying years and 1.5 million AFY on
average. But in recent years, due to a prolonged three-year drought and court-ordered pumping restrictions due to
Endangered Species Act issues, MWD has received a small fraction of its contract supply (less than 200,000 AFY).
In fact, in 2009 and 2010 MWD had to allocate its imported water for the firsttime since 1991 resulting in wide
spread mandatory water restrictions throughout Southern California.
The State of California has a basic apportionment of 4.4 m illion AFY of water from the Colorado River, although
California ha s hi storically t aken ana dditional 1 m illion A FY of s urplus w ater a nd unus ed a pportionments from
Nevada and Arizona. MWD's basic apportionment is 503,000 AFY, although until recently MWD has been able to
utilize surplus and unused apportioned water of up to 1.2 million AFY. However, the U.S. Secretary of Interior has
asserted California must develop a plan to live within its apportionment leading to development of the a Colorado
River W ater U se P Ian ha s be en de ve loped, w hich has the k ey el ement o f c ompleting a Q uantification Settlement
Agreement establishing baseline water use for each California party with rights to Colorado River water. A s such,
MWD ha s d eveloped storage and water transfer pr ograms t o boost i ts r eliability of Colorado R iver A queduct
deliveries.
Recycled Water
The City uses recycled water to meet a small portion of its overall water demands. The City realized the potential of
recycled water early on and constructed two water reclamation treatment pi ants, the Los Angeles-Glendale Water
Reclamation Plant (LAGWRP) and Donald C. Tillman Water Reclamation Plant (TWRP), to produce tertiary treated
recycled water ups tream i nstead of enl arging i ts t wo terminus WWTPs, Hyperion Treatment P lant ( HTP) and
Terminal Island Treatment Plant (TITP). In 1979, the City first began delivering recycled water to irrigate parks areas
in the Griffith Park area. Since that time recycled water deliveries have been expanded to include, but are not limited
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to, freeway landscaping, golf courses, environmental enhancement, and non-governmental industrial and commercial
uses. In 2005 almost 65,000 AFY of the City's wastewater is recycled. This includes municipal and industrial use of
1,950 AFY, or less than 1 % of the City's water supply, to offset potable demands. An additional 28,500 AFY of
recycled water is used for environmental purposes and 34,000 AFY of secondary treated water is sold to West Basin
Municipal Water District for recycling.
To further increase recycled water use, the City is in the process of developing acorn prehensive Recycled Water
Master P Ian to g reatly e xpand bo th n on-potable us e of r ecycled w ater a nd i ndirect potable us e t hrough advanced
treatment of recycled water for groundwater recharge. The goal of this master plan is to develop over 30,000 AFY of
new supply by 2018.
Wastewater
The City's wastewater system provides wastewater collection, treatment, and disposal. This system is composed of a
wastewater collection system that includes approximately 6,500 miles of major interceptors and mainline sewers, 46
pumping plants, and various other support facilities, such as corporation yards and diversion structures. The City's
treatment facilities include a large secondary treatment plant, which is located at the coast and serves the majority of
the C ity, two w ater reclamation pi ants (tertiary treatment) 1 ocated in the northern p art o f the C ity (San F ernando
Valley and Central City), and one water reclamation plant (tertiary and advanced treatment) located in the southern
most part of the City (TITP). The existing cumulative average dry weather flow (DWF) treatment capacity is 543
MOD. By 2020 additional treatment and collection system capacity will be required. This additional capacity could
be constructed at the secondary treatment plant or at the two northern water reclamation plants.
There are four WWTP within the City's service area, the TITP, HTP, TWRP and LAGWRP. Figure 9 s hows the
location of these plants.
The TWRP is a full tertiary treatment facility with capacity to treat 80 MGD; flows in excess of 80 MGD are by-
passed for treatment downstream at the HTP. The TWRP currently supplies tertiary effluent for reuse and it also
discharges to the Los Angeles River. No solids handling or processing are performed at the TWRP. Solids removed
from the treatment processes are returned to the sewer system for treatment at the HTP.
The LAGWRP serves the Glendale/Burbank area and can treat excess flow that by-pass the TWRP. The LAGWRP is
the City's oldest tertiary treatment facility and has the capacity to treat 20 MGD. Like the TWRP, the LAGWRP is
an upstream plant that treats constant flows, since it has the ability to bypass flow to the HTP for treatment. The
LAGWRP supplies effluent for reuse (primarily landscape irrigation and cooling water), with the remaining effluent
discharged to the Los Angeles River. Like the TWRP, there are no provisions for solids handling or processing at the
LAGWRP. Solids removed from the treatment processes are returned to the sewer system for treatment at the HTP.
The HTP is the City's oldest and largest wastewater treatment facility and is designed to provide full secondary
treatment for a maximum monthly flow of 450 MGD and corresponding average DWF of 413 MGD. The HTP is an
end-of-the-line plant, subject to normal diurnal and seasonal flow variation. The HTP currently exports 21 MGD of
secondary effluent to the West Basin Water Reclamation Plant, managed by the West Basin Municipal Water District
for further treatment and reuse. The remaining secondary effluent is discharged to the Santa Monica Bay via a 5-mile
ocean outfall.
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Tillman
Water
Reclamation
Plant
LA/Glendale
Water
Reclamation Plant
Terminal Island
Treatment Plant
Figure 9. City of Los Angeles Wastewater System
The fourth treatment plant, TITP, is in the vicinity of the Los Angeles Harbor. Currently, TITP has the capacity to
provide tertiary treatment and advanced treatment (microfiltration and reverse osmosis) for an average flow of 30
MOD. Like the HTP, the TITP is an end-of-the-line plant, subjected to normal diurnal and seasonal flow variation.
At the TITP, biosolids are treated to Class B levels and hauled for land application and reuse as a soil amendment in
the region.
Stormwater
The City's runoff service area consists of approximately 295,000 a cres spread throughout portions of four major
watersheds and more than 2,000 s ub-watersheds. Most of the land area is highly urbanized and impervious. A
myriad of government agencies jointly cooperate to operate the extensive runoff management system, including the
City, Los Angeles County, State of California, and Federal agencies, to protect the City's citizens and property from
flood ha zards. As a w hole t he system i ncludes flood c ontrol basins, o pen c hannels, s torm dr ains, c atch ba sins,
culverts, low-flow diversions to direct runoff to the sanitary sewer system, pumping plants, spreading grounds, and
detention basins. The stormwater system is completely separate from the wastewater system. The portion of the
runoff management system owned and operated by the City is composed of approximately 34,000 catch basins, 2,457
culverts, 157 flood control basins, and over 1,200 miles of storm drains. The runoff management system also has
approximately 2,000 outlets to the largest river in the City, the Los Angeles River, and has 315 outlets to Ballona
Creek.
Discharges oc cur throughout m ost of the s ystem i n bot h d ry a nd w et w eather. Working t ogether t he s ystem
components drain dry and wet weather from City streets into gutters and then catch basins. Catch basins route runoff
into an underground network of pipes and drains discharging the runoff either directly to the Pacific Ocean or into
inland streams and channels which may ultimately di scharge into the Pacific Ocean or to wetlands, flood control
basins, or lakes. DWFs are derived from a variety of sources including landscape irrigation runoff, street washing, car
washing, g roundwater s eepage, i llegal c onnections, hydrant flushings, c onstruction runoff, and other c ommercial
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activities. DWFs attributed to the City are estimated at 58 MGD. Wet weather flows are intermittent in nature and
potentially 1 arge v olumes are discharge dur ing w et weather ev ents. The av erage annual v olume of d ischarged
attributed to wet weather is estimated at 56,200 million gallons or approximately 172,000 AFY which is equivalent to
about 25% of the City's annual demand (City of Los Angeles, 2006b).
Water Resource Challenges
Each water resource system in the C ity faces uni que challenges. However,these individual sy stems al so face
common challenges. Common challenges include regulations, community concerns with siting of facilities, lack of
funding for infrastructure, and interagency coordination.
Water
Providing ade quate and reliable w ater supplies i n asemiarid climate presents multiple challenges. Constraints
imposed on the City's water supply are primarily driven by cycles of drought. Drought conditions have the largest
impact on t he C ity's i mported w ater s upplies. Imported water supply av ailability can vary subs tantially due t o
hydrology. Cyclical hy drologic cond itions in theeastern Sierra Nevada result in apattern ofwetand dryyears
influencing snow pack levels and ultimately deliveries to the City viathe LAA. D uring wet years deliveries have
exceeded over 400,000 AFY, while during critical droughts, only 75,000 AFY has been delivered. D roughts also
impact imported water deliveries from MWD. Potential climate change will also likely cause greater variability in
imported water. To mitigate against the effects of recurring droughts and future climate change, the City continues to
make substantial investments in groundwater, water conservation, and recycled water.
Other water supply challenges include environmental restrictions and water quality issues. The Owens Valley and
Mono Basin regions are the sources of the LAA water to the City and both regions are experiencing environmental
impacts related to withdrawals of large volumes of lake water to the LAA. Thus, diversion of LAA supplies has been
necessary f or e nvironmental m itigation i n t hese r egions r educing de liveries t o t he C ity. Also, e nvironmental
constraints i n the Sacramento-San Joaquin B ay D elta, t he s ource o f the SWP that de livers w ater to Southern
California, have greatly affected imported water deliveries to MWD. Finally, local groundwater contamination in the
San Fernando Valley has curtailed groundwater production at multiple City wells requiring wells to be taken offline.
Wastewater
System capacity is the primary driver of the City's wastewater system. Population projections prepared for the IRP
indicate system capacity will be inadequate in 2020. Additional system capacity will be required for the both the
treatment and collection system components. Additional wastewater system challenges include reducing infiltration
into the collection systems during wet-weather events and biosolids disposal (City of Los Angeles, 2006a).
Stormwater
Compliance with Total Maximum Daily Loads (TMDLs) is the major driver of the Stormwater system. Major water
bodies within the City, including the Los Angeles River, Ballona Creek, Dominguez Channel, Santa Monica Bay, and
many of the tributary channels and creeks are on the Clean Water Act 303(d) list for impairments. Most constituents
are conveyed into receiving water without treatment. Fourteen TMDLs including trash, bacteria and several heavy
metals have been adopted and more than 60 are expected to be adopted by 2012.
Additional Stormwater system challenges include: development of an approach to combine source control of urban
pollutants, r unoffv olume r eduction, and technologies to remove pol lutants from r unoff; a dministration, s ince
Stormwater affects departments throughout the City; le gislative and policy changes at the local, county, and state
levels to regulate urban runoff and provide guidelines for urban runoff reuse; and, scientific advancements since
Stormwater management inherently has many uncertainties (City of Los Angeles, 2009).
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5.2 Relationship between City of Los Angeles IRP and TWM Desktop Analysis
The following sections in this chapter describe the desktop analysis for this TWM technical report. The development
of the model, TWM options and their characterization, the combination of options into TWM alternatives, and the
simulation and evaluation of the TWM alternatives are all original to this desktop analysis and not from the City's
IRP. This c hapter, how ever, dr aws significantly from the IRP in the geographical c haracterization, t he T WM
approach (similar to the City's approach for the IRP), and the much of the data required for the analysis. Thus, the
results presented in this chapter illustrate the same general benefits that were estimated in the IRP.
The TWM options and levels of implementation presented in this case study are for illustrative example only, and
meant to demonstrate the potential benefits using realistic water resources information for a large urban watershed.
The options presented here do not necessarily reflect actual or planned implementation by the City, nor do they reflect
official policies of the City. Although the majority of data assumptions regarding costs and benefits for these options
are based on the work completed during the City's IRP, other studies and reports were utilized. This disclaimer is
also under the Notice.
5.3 Model Conceptualization and TWM Options
Based on the facilities and watershed features of the City, the project's geographic scope was divided into 4 demand
zones: San Fernando Valley (SFV), Central City (Central), Westside (West) and San Pedro (SP) (see Figure 10). The
SFV zone includes TWRP, the Central zone includes LAGWRP, the West zone includes HTP, and the SP zone
includes TITP. The Los Angeles River flows through the SFV zone, into and out of the Central zone and discharges
into the ocean in SP zone.
DOT Water
Reclamation Plant
A
LAG Water
Reclamation Plant
~^V
Termini I Island
Treatment Plant
Figure 10. Demand zones for Los Angeles total water management systems model
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TWM Options
A number of TWM options were included in the case study model. Many of the options described in this case study
are currently being implemented, in planning stages, or being considered by the City, and were included in order to
demonstrate the types of benefits that can be achieved through TWM. While these TWM options are particularly
relevant to the water resources context of Los Angeles, many of these options could benefit other regions of the U.S.
with varying degrees.
Another key aspe ct o f the case study i s to demonstrate the value of u sing a s ystems model to evaluate an urban
watershed. While t he TWM options co uld be i mplemented sep arately f or e ach water s ector, it is t he pow er o f
integration and ability to analyze the entire impact of such strategies that is unique to TWM.
The systems model built for this study includes the TWM options described below. The options are available in each
of the four demand areas in the study area. Each can be "switched" on or off in the model and different scenarios can
be run toe ompare the c apital a nd ope rating c osts as w ell a s t he w ater s upply a nd w ater qua lity be nefits of t he
different options (or combinations thereof). Appendices A through C include detailed assumptions and calculations
regarding cost, hydrologic variability, and local watershed yield estimates for these options.
Water quality i s an i mportant attribute for e ach of the TWM options, and i s m odeled for e very flow path i n the
system. The constituent selected as a p roxy for water quality impacts, either positive or negative, from TWM
alternatives was zinc. There are mainly three reasons for the selection of zinc as a proxy for water quality: (1) it is
generally a conservative constituent, which is important for the monthly time scale of the model; (2) there is a specific
monitoring pr ogram of c oncentrations f rom City which generates data to inputtothe model; a nd (3) t he
concentrations are high enough to be able to observe benefits of TWM options with impacts on w ater quality, i .e.,
some other constituents regularly monitored by the City have many data points as "non-detect," which doesn't allow
to show impacts of TWM options in their concentrations.
Water Conservation
The water conservation option specifies an overall reduction in water demand, and assumes a variety of water saving
and water efficiency programs and technologies. The conservation option can be individually selected for indoor and
outdoor water demands in each demand zone. The degree of conservation savings is specified as a percent reduction
in demand. In the WEAP model, conservation is applied directly to the indoor and outdoor "demand nodes." The
conservation percentages are applied uniformly in each month and year oft he simulation as a s calar to the input
demand projections.
Two levels of w ater co nservation w ere c onsidered i n t his s tudy: "moderate con servation" and "aggressive
conservation." For moderate conservation, the indoor and outdoor demand reduction percentages were 5% and 10%,
respectively. For aggressive conservation, t he i ndoor and outdoor reduction pe rcentages w ere 10 % and 20 %,
respectively. It should be noted these conservation savings represent additional conservation over and above what has
already occurred within the City. As noted earlier, current conservation has reduced City demands by almost 15%
from 1990 levels of water use.
Modeling w ater c onservation a ssumes a nnual op erating pr ogram c osts. The assum ptions a re ba sed on actual
conservation measures that would be implemented to achieve the levels specified in the options (see Appendix A for
more details on cost assumptions). Water quality is only impacted by the conservation options in so far as required
flow rates are reduced.
Non-potable Wastewater Recycling
Non-potable w astewater r ecycling i s de fined in t his st udy as t he co llection a nd tertiary treatment of m unicipal
wastewater flows to meet outdoor irrigation and industrial process water demands. The City currently recycles and
reuses some of its wastewater through existing facilities, but this study looks atthe costs and benefits of expanded
wastewater recycling projects.
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In the WEAP model, wastewater volumes are determined at each of the four demand zones as a percentage of the
indoor potable water usage minus losses and consumption of water. Additionally, wastewater volumes include any
outdoor flows that enter the local sewer system with specific diversions. Wastewater recycling is represented as a
"transmission link" flow pathway from the demand zone's reclamation plant to an outdoor demand node. Each water
reclamation pi ant ha s a s pecified w astewater recycling c apacity a nd a portion of the pi ant e ffluent (according to
demand, and up to capacity) is treated to tertiary standards and then conveyed through a recycled water distribution
system to meet outdoor demands.
Modeling the wastewater recycling option assumes additional and/or expanded treatment and conveyance facilities
for the use of the recycled water. It is assumed that wastewater recycling operations include treatment, pumping and
conveyance, as well as annual maintenance. These all have associated capital, fixed, and variable costs - which are
accounted for in the model.
For water quality modeling, each water reclamation plant has a specified effluent concentration for the constituent of
interest, i.e., zinc. Flows upstream of the plant have a zinc concentration but it is assumed that the plant will be able
to meet the effluent concentration in all simulated months, and the concentration of zinc is reset when the wastewater
effluent leaves the plant to a concentration equal to the standard.
For each demand zone, the water reuse pathway can be switched on or off, and a capacity for water reuse facilities is
specified. The model doesn't include an option to decouple the fire flows from the potable water system at this time.
The reason for excluding the option from the desktop analysis is that the City's potable system is practically built out.
This means that facilities have been sized to meet fire flows. Decoupling the fire flows would, in the case of Los
Angeles, represent a s ignificant ad ditional co st - to est ablish a sy stem w ith recycled water us ed for fire flows.
However, the separation between potable and non-potable systems for fire flows does have merit in new development
or in suburban areas, and potentially in the City if significant infrastructure replacement programs are implemented in
the future.
Dry Weather Urban Runoff Capture and Reuse
Dry weather u rban r unoff (DWUR) in L os A ngeles is defined as t he flows that ent er the st ormwater c ollection
infrastructure from over irrigation and other outdoor water uses (e.g., car washing). These flows are termed "dry
weather" because they are present in the stormwater system even during periods when there is no precipitation. For
this study, three options are considered for DWUR management. The first option is for DWUR to be collected and
conveyed to a dedicated DWUR treatment facility - where the treated effluent is reused to meet outdoor demands.
With the second option, DWUR is collected and conveyed to the existing WWTP through the local sewer system.
And with the third option, the DWUR persists as runoff and is collected in the existing stormwater system and then is
managed and treated as stormwater to comply with TMDL requirements before discharged to the receiving waters.
Los Angeles currently has a number of facilities for diverting DWUR, mostly in the West zone. This study looks at
the costs and benefits of existing and expanded DWUR management practices. Each demand zone is assumed to
have its own DWUR facilities and infrastructure (according to the selected option), and managed DWUR flows are
either used to offset outdoor demands or discharged to the receiving bodies of the given demand zone. Depending on
the option, the facilities required can include collection, treatment, and conveyance. Operations include treatment
and/or conveyance, as well as annual maintenance. These all have associated capital, fixed, and variable costs.
In t he WE AP m odel, the D WUR management opt ions ar e r epresented using " return flow" pathways a nd/or the
internal "reuse" parameter of the outdoor demand sites (the reader is referred to the WEAP software documentation
for more information). Depending on the option selected, return flows are used to divert a portion of the DWUR
flows (up to the specified facility capacity) to the local sewer system and WRP, and to divert the remainder of DWUR
flows to the stormwater system. The internal reuse parameter at the outdoor demand node isused to account for
DWUR treated and reused at a dedicated treatment plant. The reuse parameter acts as a reduction in demand - as a
portion of the required flow in each month is offset by "internal" management practices. The costs and benefits of the
different DWUR options are associated appropriately with these flow pathways and node parameters.
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For water quality m odeling, the D WUR options are handled differently. D ry weather urban runoff flows that are
treated (either at the local WRP or at a ne w, dedicated treatment facility) are assumed to have e ffluent pollutant
concentrations suitable for reuse for outdoor demands. D ry weather urban runoff flows that enter the stormwater
system are assumed to take on the stormwater pollutant concentrations.
In the model, for each demand zone, the DWUR management option can be specified, and a capacity for the DWUR
management facilities is specified.
Graywater
Graywater is defined as water captured from relatively "clean" indoor water usage (e.g., bathroom sink and shower
flows, clothes washers, and dishwashers) and then minimally treated for outdoor water use. This water is distinct
from "blackwater" which includes sewage water from toilets and kitchen sinks. In this study, some percentage of the
indoor water use can be collected and reused to meet outdoor demands within the same demand zone, rather than
being conveyed to the WWTP. This diverted graywater requires some treatment and pumping in order for it to be
reused onsite.
In the WEAP model, the graywater option is represented in each demand zone as a "transmission link" flow pathway
from the indoor demand node to the outdoor demand node. A constraint is applied to the transmission link to limit the
maximum amount of indoor graywater that can be reused. The graywater constraint is the product of a "graywater
potential" factor and a "coverage" factor. The graywater potential is assumed to be 65% of the total indoor water use
at any household or business that could potentially be diverted for onsite graywater reuse. The coverage factor is
variable for di fferent seen arios, and represents the extent of application of graywater systems to households and
businesses in the demand zone (e.g., 25% of all households will have graywater systems).
The gr aywater option i s assumed tor equire a dditional hous ehold p lumbing, s torage, a nd treatment facilities.
Operations require treatment and pumping, as well as annual maintenance. All of these have associated capital, fixed,
and variable costs - which are accounted for in the model.
For water quality modeling, it is assumed that the graywater sources are relatively clean at that minimal treatment is
required to produce water suitable for outdoor demands. These assumptions are implicit in the approach, but are not
explicitly modeled in WEAP.
Within the model, and at each demand node, a graywater switch can be turned on or off, and a percent diversion of
indoor water use is specified. This percent diversion includes the amount of water that can potentially be reused as
graywater, as well as the extent of application of graywater systems to households and businesses within the demand
zone. When graywater is implemented, water supplies increase and flows to the wastewater system are reduced.
It should be noted that use of g raywater systems in California is still considered an emerging practice as there are
significant regulatory issues that municipalities will need to address. However, graywater systems have been used in
small-scale demonstration projects successfully in California and full-scale elsewhere around the world.
Rainwater Harvesting
Rainwater harvesting is defined as the direct collection, storage, and use of rainwater from the rooftops of buildings.
The captured rainwater can be used to meet outdoor demands with minimal or no treatment and minimal pumping.
In the WEAP model, rainwater harvesting is represented in each demand zone as a "transmission link" flow pathway
from t he (combined) " urban node " a nd " urban c atchment" e lements t o t he out door de mand node . T he ur ban
catchment node includes all of the surface area of the demand zone, i.e., sub-watershed. Some portion of that surface
area represents the total rooftop area of buildings in the demand zone, and a decision variable in the WEAP model
indicates howmuchof the total building roof area is dedicated for rainwater harvesting. The upper limit on the
monthly a vailability of ha rvested rainwater i s t he p roduct o f t he r ooftop a rea, t he m onthly r ainfall de pth, a nd a
rainwater capture coefficient (which includes 1 osses related to storage, weather, and use patterns in the rainwater
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harvesting systems). This limit is applied as a constraint on the rainwater harvesting transmission link. See Appendix
B for detailed assumptions regarding rainfall/watershed analyses related to rainwater harvesting.
This r ainwater ha rvesting opt ion i s a ssumed tor equire o nsite rain c ollection plumbing a nd s torage. O perations
require some pumping of the captured water to its eventual use, as well as annual maintenance. All of these have
their associated capital, fixed, and variable costs - which are accounted for in the model. For water quality modeling,
the rainwater harvesting option is assumed to be a clean source of water without pollutants, in this case, without zinc,
the pollutant of interest in the model.
For each demand zone in the model, the rainwater harvesting option can be switched on or off, and the total rooftop
catchment ar ea (in the z one) is sp ecified. The un derlying ass umptions about ca ptured rainwater s torage, a nd
rainwater capture efficiency are also specified within the model.
Indirect Potable Reuse for Groundwater Recharge
Based on current regulatory constraints, recharging groundwater aquifers in the Los Angeles basin will involve
advanced treatment be yond tertiary treatment of w astewater. The standard practice for advanced treatment is
microfiltration and Reverse O smosis (MF/RO). This option assumes a MF/RO treatment process adjacentto the
WRP, and then this advanced-treated recycled water would be conveyed to existing spreading grounds in the San
Fernando groundwater basin for recharge using natural percolation. The recycled water would then travel through the
groundwater basin for a number of years to be extracted for potable use.
In the WEAP model, the recharge of groundwater with WRP effluent option is represented in the SFV and Central
demand zones as a "return flow" pathway from the reclamation plant to the groundwater basin (the other two demand
zones do not manage the groundwater for water supplies). A decision variable in the model allows specification of
the percent of WRP effluent that is diverted to the basin for recharge.
For water quality modeling, the recharge water is effluent from the reclamation plants - with the associated effluent
pollutant concentration. WEAP doe s not track w ater quality i n g roundwater ba sins du e t o t he c omplexity a nd
uncertainty of mixing in different basins. The initial conditions of groundwater storage and zinc concentrations in the
basin are not known. Thus, an outflow concentration is specified for groundwater extractions.
In the model, groundwater recharge from the water reclamation plant can be switched on or off for each demand zone,
and for each zone is specified the percent of the WRP effluent that is directed for groundwater recharge.
Centralized and Decentralized Stormwater Recharge
Two options for groundwater recharge with stormwater are included in this study: centralized Stormwater collection
and recharge, and decentralized stormwater recharge.
Centralized stormwater recharge is defined as the diversion of some portion of collected stormwater flows into
conveyance infrastructure that carries the stormwater to groundwater recharge facilities (either percolation basins, or
injection wells). In the WEAP model, the centralized stormwater recharge option is represented in each demand zone
as a flow from the combined "urban node" and "urban catchment." Rainwater in the urban catchment that does not
naturally infiltrate into the ground, and that is not diverted as direct rain harvesting, will become stormwater in each
demand zone. A decision variable for the capacity of the centralized stormwater recharge facilities (in each demand
zone) is included in the model, and is applied as a constraint to the transmission link. Groundwater recharge is
"forced" in WEAP by using a "dummy" demand node of arbitrarily high value. W hen performing the supply and
demand a llocation, W EAP w ill s end a vailable s tormwater t o t he g roundwater ba sin, up t o t he c apacity of t he
centralized recharge facilities, as it tries to meet the dummy demand.
Forthe centralized option, itis a ssumed that conveyance and recharge facilities are required. Operations include
pumping, treatment, and recharge. Annual maintenance is also required. These elements all have associated capital,
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fixed, and variable costs - which are accounted for in the model. Water quality pollutant concentrations are specified
and tracked in the model for the urban stormwater flows.
Decentralized stormwater recharge is defined as allowing additional infiltration of stormwater to take place at smaller
sites scattered throughout the demand zone. Increased infiltration of localized stormwater flows takes place through
"non-conventional" stormwater entities, such as swales and percolation ponds. In the WEAP model, the decentralized
stormwater r echarge opt ion is r epresented in each demand zone a s a n a djusted r unoff/infiltration r atio of t he
stormwater volumes at the urban catchment nodes. Rainwater is specified in WEAP at the urban catchments as a time
series of rainfall depth per month. The monthly rainfall volume (product of rain depth and catchment surface area) is
routed along two pathways - runoff and infiltration. The proportion of rain volumes becoming runoff or infiltrate are
specified as si mple pe rcentages of the total flow. T he d ecentralized stormwater recharge op tion increases the
proportion of rain water infiltrating to the ground, while decreasing the proportion becoming runoff. This approach
captures the essence of d ecentralized s tormwater m anagement m ade up of s mall st ormwater r echarge facilities
scattered throughout the demand zone.
For the decentralized option, it is assumed that the stormwater management infrastructure (swales and ponds) need to
be constructed. Operations are minimal, but the facilities require annual maintenance. These elements all have
associated capital, fixed, and variable costs - which a re a ccounted for i nthe model. W ater quality pollutant
concentrations are specified and tracked in the model for the urban stormwater flows.
Both the centralized and decentralized options can be switched on or off for each demand zone. For the centralized
option, the capacity of the recharge facilities is specified, and for the decentralized option the total area of "non-
conventional" stormwater facilities and their i nfiltration coefficient are specified. The c onceptual m odel of these
options is described in Appendix B.
5.4 Systems Model
As part of this study, a high-level decision support model was developed using the WEAP software to demonstrate
how TWM alternatives would p erform a gainst traditional, s egmented a nd non-integrated approaches to water
management. The model was constructed to represent the main water resources features of the City. The model is
intended to be used at the planning level of d etail and so aggregates many of the features of the potable-water,
wastewater, and stormwater systems into the four demand zones described above (along with the relevant connections
between zones).
The WEAP model tracks the urban water supply and demand balance, supply reliability, total lifecycle costs, and
water quality of receiving waters. The TWM options described above are programmed into the model for each zone
and can be selected and specified (in terms of size and extent) in the setup of different scenarios to run and compare.
The model simulates how integrated water supply and water quality management can provide increased opportunities
for achieving urban system goals that would not exist in single-purpose, traditional planning.
WEAP Software
WEAP is a software package developed by the Stockholm Environment Institute that allows integrated modeling for
water resources planning, management, and decision- making. WEAP allows users to build a customized model of
their water i nfrastructure as on e interconnected s ystem including w ater s upply, di stribution, treatment,
recycling/reuse, and disposal infrastructure. The so ftware pe rforms a m ass ba lance t hroughout the system and
allocates water based on user-defined demand priorities and supply preferences. In the analysis, important system
performance measures can be defined and tracked including reliability, cost, and water quality. Models are built in
WEAP with a user-friendly interface consisting of a graphical schematic of the system and a set of data tables and
graphs. The user can then run simulations for various scenarios and view results in terms of water reliability, water
quality, and cost. Figure 11 shows a sample of the graphical interfaces of WEAP.
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Figure 11. Screen capture of WEAR interfaces
Complete doc umentation of WEAP is included with the software in i ts comprehensive us er manual, a s w ell as
through the SEI website and online tutorials. However, brief descriptions of the relevant components and features of
WEAP are provided here.
WEAP Model Components
Water resources systems are described and modeled in WEAP using the following basic components.
Demand Nodes
Demand nodes are used to specify water demands. Demands can be further specified by type, such as single family
homes, multi-family hornes, commercial, industrial demands, and/or indoorvs. outdoor. Demands are entered as
projections into the future. Demand nodes also have important parameters, including water loss and consumption
rates, water reuse rates, and demand reduction (conservation) rates. For the Los Angeles case study, each "demand
zone" was made up of two demand nodes - indoor demands and outdoor demands.
Wastewater Treatment Plants
WWTPs receive water from demand nodes or catchments and represent the treatment of water to some specified
effluent standard. The treatment plants also have a specified capacity, and any flows entering the plant in excess of
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the capacity pass downstream, untreated. F or the Los Angeles case study, each demand zone uses a WWTP to
represent the water reclamation facility.
Catchments
Catchments represent watersheds or sub-watersheds. Catchments have a sp ecified surface area and are associated
with a specified time-series of rainfall (along with a number of other weather and agricultural parameters that were
not used in this study). The area and rainfall parameters of the catchments are used to determine total monthly
rainfall volumes. The rainfall volume is then routed as either runoff or groundwater infiltration. For the Los Angeles
case s tudy, each demand zone i s r epresented as an urban catchment - with its r espective sur face area and
runoff/infiltration coefficients.
Groundwater Basins
Groundwater basins are nodes which track inflows, outflows, and storage volumes. The groundwater basins require a
specified time series of "n atural recharge" flows, as well as asp ecified storage capa city. A maximum monthly
withdrawal rate can also be specified for the groundwater basins. Outflows from demand nodes, catchments, or water
treatment plants can be used to represent various infiltrations or recharge processes. And the groundwater basins can
have their own outflows to represent groundwater pumping. For the Los Angeles case study, each demand zone has a
groundwater basin; but only two are modeled, as only the SFV and Central basins are actively managed by the city for
water supply.
Other Supplies
Other supplies represent generic sources of water and can be used to model entities such as desalination plants or
imported water supplies. Other supplies are specified with a time series of inflows. WEAP allocates water from the
other supplies up to the inflow value. Any inflow water not used in the time step will be lost from the system i.e.,
other supplies have no storage. In the Los Angeles case study, other supplies were used to represent the two imported
water supplies, i.e., LAA and MWD.
Transmission Links
Transmission links are flow pathways that actively convey water between two system elements. WEAP performs a
prioritized demand-supply allocation analysis that routes water from supplies to demands through transmission links.
Transmission links can be specified with monthly flow capacities. WEAP will allocate water supplies according to
their availability and the ability for transmission links to carry the flows. Transmission links can also be specified
with loss fractions.
Return Flows
Return flows are flow pathways that passively convey water between two system elements. Return flows exiting a
demand node or WWTP node are each given a percentage of the total node effluent (with the sum equaling 100%).
WEAP calculates the total effluent, and routes water in proportion to the return flow routing percentages. R eturn
flows can also be specified with loss fractions.
WEAP Model Calculations
WEAP performs three general kinds of calculations during a simulation. These include a water supply/demand mass
balance, a water quality mass balance, and a financial analysis (including costs and benefits).
WEAP i ncludes a pow erful, systems-view a llocation a Igorithm for pe rforming t he s upply a nd de mand ba lance
throughout the modeled area. The network of supply, demand, and treatment nodes and the flow pathways between
them ar e r epresented as a s ystem of equa tions that ar e so Ived simultaneously by WE AP us ing 1 inear al gebra
algorithms. D emands a re ser ved by suppl y so urces acco rding t o user-defined de mand pr iorities a nd us ing us er-
defined supply preferences. In the case of water shortages, the priorities are used to determine the allocated volumes
of water to each demand node. These calculations takes place 'behind the scenes' in WEAP, but provide a powerful
tool for the integrated analysis of water systems with multiple supply sources, demand nodes, and flow options.
30
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WEAP is able to track the mass balance and dynamic behavior of a number of built-in water quality parameters, such
as total suspended solids (TSS), biochemical oxy gen de mand (BOD), dissolved oxygen (DO), and temperature.
Additionally, the user may define other constituents or pollutants to track over time and space. WEAP includes a
number of built-in methods for modeling the different water quality constituents - including methods for conservative
pollutants, decaying pollutants, and specialized methods for BOD and DO. In this study only a single, representative,
and conservative pollutant was modeled (zinc). C alculations for zinc concentrations in the model required only a
simple mass balance at nodes in the model where flows mixed. The weighted average of pollutant concentrations of
the mixing streams was taken as the combined concentration.
WEAP includes a cost layer which allows specification of capital, fixed annual, and variable operating costs at each
node and flow pathway in the system. Costs can be specified for model elements to represent WWTP facilities and
processes, de mand m anagement pr ograms, c onveyance t hrough t ransmission 1 inks a nd r eturn flows, facilities and
pumping at groundwater basins, acquisition and conveyance of imported supplies, etc. Capital costs are amortized at
an assumed discount rate, fixed costs are incurred each year in the simulation, and variable costs are applied per unit
of flow. WEAP performs a financial analysis on all of the costs to produce a total Net Present Value for the simulated
scenario. WEAP also reports the Net Cost of the scenario and the Average Cost of Water for the scenario.
Running Simulations and Viewing Output with WEAP
WEAP allows the setup and simulation of various water resources planning scenarios. Any of the input variables (or
combinations of variables) can be changed and run as a separate scenario. WEAP will simulate the performance of
the scenario on a monthly time step for any future period defined by the user. D uring t he s imulation, WEAP
determines the water quantity and quality mass balances and calculates the operational costs.
WEAP has built in tools to conveniently manage the scenarios (e.g., save scenarios, open saved scenarios, and define
scenarios based on inherited values from a parent scenario). Within WEAP scenario results can be viewed
individually or c ompared against on e a nother. A dditionally, W EAP out put c an be e xported t o Microsoft E xcel
spreadsheets for further analysis or presentation.
WEAP has a dynamic output screen that provides flexibility and diverse formatting options for viewing simulation
results. Results can be viewed for any of the system metrics. Examples include:
Demand projections
Supply requirements at demand nodes (after conservation, etc)
Supply reliability
Supply mix from the different water sources
Reliance on imported water supplies
Stream flow and in-stream water quality
Groundwater inflows/outflows and storage volume
Capital, fixed, and variable costs
Financial analysis (e.g., average water cost, net cost)
31
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Data Requirements for Input to WEAP
WEAP provides a lot of flexibility for the input of data. Input data can be entered directly into the WEAP interface,
imported through a specially formatted excel spreadsheet, or read directly from an external file. The following data
are required in order to fully define a water system/scenario in WEAP.
Demand Data
Specify the "activity level" at demand nodes and the water use rate for that activity [e.g., demand at a node is
calculated as the number of people in the node ("activity") multiplied by the gallons of water used per person
per year ("use rate")].
Demands can be d isaggregated at the demand node level (e.g., household w ater us e c an be broken upby
water used for showers, toilets, drinking, or washing).
Demands are entered as annual volumes though monthly variations can be applied to give higher seasonal
resolution.
Supply Data
Water su pplies to the sy stem can be de fined as r ivers, groundwater ba sins, 1 ocal sur face bod ies, r ain
catchments (runoff), or imported/transfer water connections to other agencies or basins.
Each supply can be specified differently, either as user-defined inflow series, or calculated based on
hydrology (using "water year types" or calculated based on rainfall and runoff).
Constraints can be added to the supply sources and used to represent various capacities on the supply (e.g.,
well capacities, conveyance capacities, or contractual capacities).
Treatment and Conveyance Capacities
Specify the capacities of water treatment plants.
Specify the capacities of conveyance pipelines or well fields.
Water Quality Data
The user enters the constituent concentrations at the various supply sources and the removal rates atthe
treatment plants.
During each time step WEAP calculates a water quality mass balance for each constituent at all of the nodes
and arcs in the system.
Cost and Benefit Data
The user may specify the levels of costs and benefits for different supply elements, including: capital costs for
new projects, fixed O&M costs, as well as variable O&M costs.
Costs and benefits are entered for supply sources, flow pathways, treatment plants, and demand management
programs.
Financial parameters, such as discount and inflation rates, are entered to calculate net costs, net-present-value
costs, and 'total cost of water' values.
Model Description
A high-level, integrated systems r epresentation of the City was prog rammed i n the WE AP software using the
previously defined four demand zones - SFV, Central, West, and SP. Each of these four demand zones is included as
32
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an identical "module" inWEAP. Figure 12 shows a representative schematic for the SFV demand zone "module."
Figure 12 includes the basic model elements: an indoor and outdoor demand node, i.e., SFV Outdoor Demand and
SFV Indoor Demand, a wastewater treatment and reclamation plant (TWRP), an urban catchment node (SFV Urban
Catchment), a g roundwaterba sin (SFV G roundwater B asin), a nd a 11 o f t he flows between entities ( called
"transmission links" in WEAP) and return flows. Figure 12 shows inflows into the demand nodes, which represent
the sources that can supply those demands. Included is, for example, a flow between SFV Indoor Demand and SFV
Outdoor demand, which is representing graywater. The attributes of that graywater flow are established in a different
layer in WEAP, where flows, capacities, costs, etc. can be included. The SFV "Dummy" variables for WWTP return
flow and for groundwater are elements that allow WEAP to establish a specific flow, as opposed to just a flow that
results from WEAP internal cal culations. This m odule is r epeated for a 11 of t he C ity a reas, w ith c orresponding
interconnections such as the Los Angeles River and process flows between upstream and downstream WWTPs.
Demand (Red), Catchment (Green), orTreatment Plant (Brown)
FlowSplit Element
Storage Element
Inflows
Outflows and Return Flows
Tilman WRP
SFV Dummy WWTP
Figure 12. Representative schematic of demand zone 'module' in WEAP
The module for each demand zone characterizes the water, wastewater, and stormwater systems for the City, and the
TWM options investigated in this study. The potable water system is described by the indoor and outdoor demand
nodes with the transmission links coming from the imported supplies (not shown in Figure 12) and the groundwater
basin. The transmission link between the indoor and outdoor demands represents the option for graywater reuse. The
wastewater sy stem i s de scribed by t he WWTP, w ith a ssociated i nflows from t he de mand node s, a nd a ssociated
outflows. Wastewater recycling and recharge a re r epresented as the transmission link and r eturn flow from t he
WWTP to the outdoor demand node and to the groundwater basin, respectively. Finally, the stormwater system is
described by the urban catchment, the urban node, and the "dummy" demand node s draining into the groundwater
basin and the river. Rainwater harvesting is represented as the transmission link from the urban node to the outdoor
demand node (SFV Urban Node and SFV Outdoor Demand in Figure 12). And the centralized and decentralized
stormwater recharge options are represented as the various flow pathways out of the urban catchment and urban node.
33
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Within WEAP, calculations take place for the water supply and demand mass balance, the water quality mass balance,
and the financial analysis - all according to the schematic as shown in Figure 12.
Figure 12 pr esents a s ummary of one o f the de mand z ones in t he m odel. The de mand z ones, how ever, a re
interconnected in the model (as in real life) by the following flow paths: raw wastewater can bypass the TWRP and
LAGWRP to be routed and treated at HTP; biosolids and process flows from TWRP and LAGWRP are discharged to
the collection system and flow downstream to HTP; and the Los Angeles River flows in the SFV zone receiving
return flows and flows into the Central zone and eventually into the TITP.
Total Water Management Options and Model Interface
To facilitate the use of the WEAP model as a decision support tool, a customized user-interface was developed in MS
Excel. Data can be easily imported to WEAP from Excel, and Excel provides a very convenient and flexible platform
for cr eating a us er-friendly "cont rol pa nel" an d for pe rforming ne cessary pre -processing cal culations o utside o f
WEAP. The control panel contains switches and input cells for selecting TWM options and specifying facilities'
capacities as decision variables. A screen-shot of the Excel control panel is shown in Figure 13.
Data Management and Programming
WEAP pr ovides a r elatively s imple, bu t comprehensive e nvironment for pr ogramming a nd a nalyzing TWM and
urban water resources management. W EAP contains a database for storing input and output data, and a powerful
calculation engine. WEAP's internal database stores and processes com plex input data and also allows flexible
viewing of the modeled results from various scenario simulations. The calculation engine performs the supply and
demand calculations, as well as derives the resulting cost and water quality values.
To solve the supply and demand calculations in WEAP, the network of supply, demand, and treatment nodes and the
flow pathways between them are represented as a system of equations that are solved simultaneously by WEAP using
linear programming algorithms. Demands are served by supply sources according to user-defined demand priorities
and using user-defined supply preferences. In the case of w ater shortages, the priorities are used to determine the
reduced allocations of water to each demand node. These calculations take place "behind the scenes" in WEAP, but
provide a powerful tool for the integrated analysis of water systems with multiple supply sources, multiple demand
nodes, and multiple flow options.
The setup and programming of a model in WEAP involves first drawing the system on the schematic layer (demand
nodes, treatment plants, groundwater basins, and connecting pathways), and then entering data into the data base to
describe t he sy stem de mand and hydrology projections, facility cap acities, routing r ules, cost p arameters, water
quality parameters, and any other system constraints. D ata can be entered into the model directly through WEAP's
interface, through a specially formatted data import spreadsheet, or read from external data files.
34
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Control Panel for Los Angeles Total Water Management Model
San Fernando Valley
Conservation
Q Indoor Conservation
fj] Outdoor Conservation
Waste Water Reuse
D WRP to Recharge
D WRP to Reuse (Outdoor Demands)
Percent of Demand - Indoor Conservation
Percent of Demand - Outdoor Conservation
Percent of WRP Effluent to Recharge
Capacity of WRP to Recharge Facilities
Capacity of Reuse facilities (final total)
Capacity of WRP Treatment Plant (final total)
Note: Existing Capacity of Reuse facilities (reference)
Note: Existing Capacity of WRP Treatment Plant (reference)
Dry Weather Urban Runoff
|- Select Option
O DWUR to Local Sewer System
O DWUR to Dedicated Treat. Plant (local reuse)
ฎ Persists as Runoff (treatment for TMDLs)
J5JMGD Capacity of DWUR Capture Facilities
Alternative Sources
HH Greywater Reuse
n Rainwater Capture
Storm Water
n Centralized Storm Water Recharge
D De Centralized Storm Water Recharge
Sub Area Designations and Runoff Coefficients
Sub Area Type
Pervious
Impervious
De Centralized Stormwater
Groundwater
Groundwater Pumping Facilties Capacity
Annual Contract Pumping Volume
GW Storage Initial Reference Volume
Acres
Effective Percent of Indoor Demand to Greywater
Rain Capture Catchment Area
Coefficient of Captured Rain that is Used (not lost)
Capacity of Centralized Storm Water Recharge Facilities
%Area
46
54
0
0.18
0.95
0.03
Existing
114.29
43,660
0
0.00
0
AF
Add'I Total
114.29 cfs
43660 AFY
Figure 13. Screen capture of the management panel forthe model developed in Microsoftฎ Office Excel
TWM Alternatives
TWM options are specific projects or programs that can be implemented to manage runoff, increase supply, reduce
demand, or r echarge g roundwater. As stated in Chapters, it i s ne cessary t o combine these TWM opt ions i nto
complete alternatives in order to be evaluated (WEAP software uses the term "Scenarios" for alternatives).
35
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To demonstrate the benefits of TWM, three alternatives were developed:
1. Baseline - represents traditional planning, or status quo
2. TWM A Iternative 1 : Water Supply - represents a T WM a pproach with emphasis on improving supply
reliability
3. TWM Alternative 2: Manage Runoff- represents a TWM approach with emphasis on improving water
quality through stormwater management
As F igure 14 shows, there ar e som e meaningful di fferences be tween the t wo TWM al ternatives and Baseline
Alternative. TWM Alternative 1 "pushes the envelope" with regards to reduction of the City's dependence on
imported water supplies. S ignificant conservation levels, both for indoor and outdoor demands are included, along
with aggressive levels of recycled water, groundwater recharge and graywater system implementation. Additionally,
it includes facilities to beneficially use DWUR.
Options and Settings
Conservation
Indoor Conservation Switch
Indoor Conservation - Percent of Demand (additional from current levels)
Outdoor Conservation Switch
Outdoor Conservation - Percent of Demand (additional from current levels)
Recycled Water Recharge
Recycled Water Recharge Switch
Capacity of Recharge Facilities
Recycled Water Use (Excluding Existing Uses and Recharge)
Additional Recycled WaterSwitch
Recycled Water for Outdoor Demands (additional to existing)
On-Site Sources
Grey water Switch
Percentage of Buildings with Systems for Use of Greywater
Rainwater On-Site Capture
Total Rain Capture Area
Dry Weather Urban Runoff (DWUR)
DWUR Managed but Not Beneficially Used
DWUR Dedicated Treatment for Beneficial Use Switch
Capacity of DWUR Dedicated Treatment Facilities for Beneficial Use
Stormwater infiltration
Decentralized Stormwater Infiltration Switch
Centralized (Large-Scale) Stormwater Infiltration Switch
Capacity Centralized Stormwater Facilities for Recharge
Units
switch
[MGD]
switch
[MGD]
switch
[AC]
switch
switch
[MGD]
switch
switch
[MGD]
Baseline Alternative 1 Alternative 2
Base Case Water Supply Manage Runoff
No
0%
No
0%
No
0
No
0
No
0%
No
0
Yes
No
0
No
No
0
Yes
10%
Yes
20%
Yes
80
Yes
10
Yes
20%
No
0
No
Yes
9
No
No
0
Yes
5%
Yes
10%
Yes
80
No
0
No
0%
Yes
1,150
Yes
No
0
No
Yes
10
Figure 14. Options and settings included in the baseline and total water management alternatives
TWM A Iternative 2 also includes indoor and outdoor c onservation but at 1 ower 1 evels. TWM A Iternative 2 also
includes options for rainwater capture and for s tormwater (wet-weather) recharge, while treating the DWUR for
compliance with TMDLs. The Baseline Alternative includes no TWM option although it also assumes treating the
DWUR for compliance with TMDLs. Baseline represents the status quo approach for Los Angeles in which the City
is heavily reliant on imported water.
Emergency and Climate Change Scenarios
Two scenarios were run in this study related to two elements of risk and uncertainty associated with water supply in
the Los Angeles area: (1) earthquake emergency scenario and (2) climate change scenario.
36
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Earthquake Emergency Scenario
This emergency scenario was set up simply by assuming an earthquake that would significantly di srupt imported
supply from MWD, to the Los Angeles area. The model did not assign specific probabilities for this scenario. The
analysis consisted in selecting one month simulated by WEAP, in the year 2030 (2030 demands) and eliminating the
MWD supply from the supply mix of resources. Results for the Baseline and the two TWM Alternatives are then
compared.
Climate Change Scenario
This scenario was set up by assuming reductions in imported supply by MWD and the LAA due to climate change
conditions. The analysis consisted in establishing a time series of forecasted reductions of MWD and LAA supplies
based on data for deliveries from northern California through the SWP (DWR, 2007). The 2007 reliability report by
the DWR presents forecasted reductions with more restrictive flow targets due to required ecological flows in the
Sacramento-San Joaquin Bay Delta and with climate change (specifically using the global climate model (GCM), and
the emission scenario A2).
MWD de livery r eductions w ere ba sed on t he flows from N orthern C alifornia toe ontractors 1 ocated i n Southern
California (known as SWP Table A Deliveries) and the reduction of these deliveries. For the case of MWD, estimates
of reduction in Table A Deliveries were adjusted based on the fact that MWD can count on a mix of supplies other
than SWP (such as Colorado River, storage and transfers) which reduce impacts of SWP supply reductions.
LAA water r eductions w ere estimated based on t he di fference between the Table A de liveries w ith and without
climate change reported in the DWR's 2007 reliability report. The same difference is assumed to apply to the LAA
system due to the fact that the source is subject to a fairly similar hydrology and snowfall/precipitation pattern than
the SWP.
The estimated reductions in imported supply are input into WEAP which simulates the TWM alternatives with and
without cl imate cha nge an d compares t o the ba seline unde r the sam e condi tions. Appendix C presents a more
detailed discussion on the modeling of hydrology for imported supply in WEAP.
5.5 Case Study Results
The B aseline and two TWM A Iternatives ana lyses i n WEAP gi ve us obj ective i nformation about m any of t he
variables of interest in making decisions. The results listed below include elements of water balance and reliability,
effects of TWM alternatives on the environment, and financial results. Results of the climate change and earthquake
emergency scenarios are also presented in terms of impacts on supply reliability.
Water Balance and Reliability
For this TWM case study, a monthly time step was used for the WEAP model. This decision was made because of
the seasonal nature of water demands and supplies for the City. Figure 15 shows the demand in the SFV demand
zone (all areas show a similar demand pattern). As the figure shows, the majority of s easonal variability is due to
outdoor demands, while indoor demand remains relatively constant (with the exception of growth and some small
variation due to weather). Outdoor water use in the City is highly variable due to evapotranspiration (ET) that drives
irrigation demands. In addition to seasonal variability, there is also variability in demand year-to-year. This yearly
variability is also due to weather. Demand in hot and dry years is higher than demand in cooler/wet years, and this is
reflected in the time series presented in Figure 15. The weather associated with each year in the projection from 2010
to 2033 i s linked to the historical record 1980-2003. As explained in Appendices B and C, ahistorical record is
imposed in the model for future years.
37
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35,000
Jan-10 Jan-15 Jan-20 Jan-25 Jan-30
Months
SFV Indoor Demand SFV Outdoor Demand
Figure 15. Monthly water demands for San Fernando Valley zone (based on 1980-2003 Weather)
By design, the TWM Alternative 1 (water supply emphasis) had very aggressive water conservation, reducing water
demands by 16% from the Baseline. A Iternative 2 (runoff management emphasis) had moderate levels of w ater
conservation, reducing water demands by 7% from the Baseline. The impact of these conservation assumptions are
illustrated clearly in the differences in total water demand presented in Figure 16. Under the Baseline, projected
water demands in the year 2030 are 760,000 AFY, while projected water demands for TWM Alternative 1 and TWM
Alternative 2 were 648,000 AFY and 718,000 AFY, respectively.
760,000
740,000
720,000
ฃ 700,000
<
~ 680,000
c
| 660,000
(D
30
(D
Q.
C
r>
p*
5'
o
(D
3
QJ
Demand Percent Reduction over Baseline
Figure 16. Projected total water demand for baseline and total water management alternatives
38
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The seasonal demands are supplied by the different sources of supply available in each alternative and the Baseline.
Figure 17 shows the supply mix time series for the Baseline, between 2010 and 2033 on an annual basis. The figure
shows a significant reliance on i mported supply, from LAA and MWD, which are by far the main sources in the
period simulated.
900,000
800,000 -
700,000
600,000
500,000
= 400,000
Q.
300,000
200,000
100,000
2010
2015
2020
2025
2030
Groundwater Recycled LAG RecycledTilman Imported LAA Imported MWD
Figure 17. Mix of water supplies for baseline
The variability in the use of sources in Figure 17 is dues to the hydrologic variation of some of those sources. In this
figure and subsequent figures, the hydrology imposed in the demand years from 20101 o 2033 c orresponds to the
historical period between 1982 and 2003. Figure 17 shows a significant decrease in LAA water from 2018 to 2024
and a gain from 2028 to 2 033, c orresponding tod roughts i n t he h istorical record. During t hese drought pe riods
impacting the LAA system, MWD supply is purchased. However, this figure does not show water supply shortages
from MWD t hat ar e g enerally cor related with drought condi tions for t he L AA sy stem (see F igure 20 for w ater
shortages for the Baseline and TWM Alternatives).
For comparison, Figures 18 and 19 shows the supply mix for TWM Alternatives 1 and 2, which shows a significant
increase in local supplies and a great reduction in imported supplies i.e., LAA and MWD, compared to the Baseline.
Conservation, groundwater, recycled water and graywater significantly contribute to the overall water supply. For
both TWM Alternatives, groundwater is significantly increased through recharge of stormwater and highly treated
recycled water. In both alternatives (Figures 18 and 19) we can observe a de crease in groundwater production in
2032. This corresponds to a locally dry year, which reduces the amount of stormwater being recharged. As explained
in the modeling s ection and A ppendix A, g roundwater m odeling i n the s ystems model w as s Amplified to a m ass
balance be cause t he initial g roundwater ba sin 1 evels were n ot av ailable for t he m odel. A g roundwater n umerical
model of the basin may simulate a less significant reduction in supply due to the combination of the low storage and
the dry year. The WEAP model, however, does keep track of groundwater use with a level of accuracy adequate for
this analysis and shows the significance of that supply in the overall supply mix.
39
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800,000
700,000 -
600,000
< 500,000
3; 400,000
3
in
*j 300,000
g
200,000
100,000
I Conservation
I Greywater Reused
I Groundwater
Imported LAA
Recycled LAG
Imported MWD
I DWUR Reused
Figure 18. Mix of water supplies for total water management alternative 1
900,000
0
2010
2015
2020
2025
2030
I Conservation
Recycled LAG
Imported LAA
I Groundwater
I Centralized Stormwater Recharge
Imported MWD
Figure 19. Mix of Water Supplies for total water management alternative 2
40
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The main differences between Figures 18 and 19 is that there is more water conservation and graywater being
implemented in F igure 18. T herefore, there i s 1 ess i mported w ater (LAA a nd M WD) i n F igure 18 than i n 1 9.
However, Figure 19 does have considerably less imported water than in Figure 17 (the Baseline).
Figures 17, 18 a nd 19 on ly show the supply delivered to the demands in the demand zones, but do not show the
supply deficits when they exi st. Figure 20 s hows the supply deficits ob served for a 11 three alternatives. Not
surprisingly, t he B aseline had the g reatest s upply de ficits, b oth i n num ber and i n m agnitude o f s hortage. These
supply deficits are directly correlated to the dependency on imported supply (LAA and MWD), as these sources of
water are highly vulnerable to droughts.
Unmet Demand (AFY)
^u,uuu
on nnn
oU,UUU
vn nnn
/u,uuu
fin nnn
DU,UUU
rr\ nnn
DU,UUU
An nnn
on nnn
3U,UUU
">n nnn
zu,uuu
1 n nnn
J.U,UUU
I , I .
O LD O LD O
*H *H (N CM CO
00000
CM CM CM CM CM
Baseline TWMAItl TWMAIt2
Figure 20. Water supply deficits for baseline and total water management alternatives
The largest water supply deficit occurred in year 2020 for the Baseline, which corresponded to a repeat of the 1990
drought conditions and results in an unmet demand of almost 80,000 AFY. TWM Alternative 2 only had one year of
supply deficit, which corresponded to the 1991 drought year. Only TWM Alternative 1 had no water supply deficits,
as this alternative had much greater levels of water conservation and implemented graywater systems.
Effects of TWM on Environment
The TWM alternatives can impact the system in many different ways. In this study we established three metrics
related to environment: (1) groundwater levels; (2) water quality in the Los Angeles River; and (3) GHG emissions.
Energy consumption in every alternative and the Baseline can also be used to define air emissions for the Los Angeles
area based on assumptions about the fuel mix used to generate energy in the region. With the assumed mix of fuels
41
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for energy generation (and hydropower), pollutant emissions (other than GHGs) can be approximated. However, in
this study we have not added any other pollutant emissions except GHGs.
Groundwater levels
The TWM model developed in WEAP includes the groundwater basin in the SFV where recharge of advanced treated
recycled water and wet weather flows can occur. Within the model, the storage element was programmed to track net
storage as a result of three actions:
1) Pumping to satisfy demands - outflow
2) Recharge of advanced treated recycled water - inflow
3) Enhanced recharge of wet weather flows - inflow
Even though the model tracks groundwater storage, the actual storage values estimated by WEAP in this study are not
representative of what could be observed in real conditions. The reason is that the initial storage value given to
WEAP is an arbitrary reference value (given the difficulty in obtaining actual groundwater basin levels for the SFV
zone). Additionally, the natural inflows and outflows are not strictly represented in the model and the groundwater
pumping activity of other users (outside of Los Angeles) r equired m ore de tailed analysis than this study could
warrant.
The assumption in this model is that the natural inflows and outflows and the pumping by others take place along with
the three storage elements (listed above) which can be controlled in the model. Actual storage values output by
WEAP are not predictive of what the field conditions actually are, but the comparative trends in storage between the
Baseline and the TWM Alternatives are valid and illustrative of positive or negative impacts to the basin as a result of
the management decisions simulated in the model. Therefore, if everything else is equal for the three alternatives, the
rationale is that the actions simulated in WEAP for a specific alternative will result in more or less storage compared
to the other alternatives simulated. Figure 21 presents the comparison of groundwater storage between the TWM
Alternatives on a monthly basis, as compared to the Baseline reference. In the figure, the Baseline reference is a flat
line with a value of zero. The trends plotted in Figure 21 are the result of subtracting the simulated Baseline storage
from the storage simulated for each TWM alternative.
Figure 21 shows that TWM A Iternatives 1 and 2 a re both significantly be tter than t he ba seline, e ven though the
pumping rates significantly increase. The reason for the improvement in groundwater levels in relation to the baseline
is the great a mounts of recharge t aking pi ace a s pa rt of the TWM alternatives. InFigure21, thereason TWM
Alternative 1, which has less groundwater recharge than TWM Alternative 2, presents better storage results is that
TWM Alternative 2 presents more pumping. Given that TWM Alternative 2 has sources that contribute less to the
overall supply mix compared to TWM Alternative 1, we have allowed more pumping in the simulation under TWM
Alternative 2, relative to TWM Alternative 1. Even with the additional pumping, storage is significantly better than
in the baseline (not shown in the figure but corresponding to a value of zero along the x-axis).
42
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in
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as
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250,000
200,000
150,000
100,000
50,000
c
CD
O
CM
C
CD
LO
CM
C
CD
O
m
c
CD
Months
TWMAItl TWMAIt2
Note: Baseline represented as a line along X-axis with value of zero.
Figure 21. Groundwater storage or total water management alternatives relative to baseline
Water Quality
Water quality impacts were measured in the Los Angeles River using zinc as a proxy for other pollutants of interest as
explained above. WEAP tracks zinc in every flow route and computes concentrations and loading at specific points
of interest in the Los A ngeles R iver. Specifically, r eturn flow nod es w here us ed as sampling 1 ocations i n t he
simulation.
Figure 22 indicates that there is seasonality in the zinc loads along the river for the baseline, with higher loads during
the wet season (which in Southern California corresponds to the period between November and March) and lower
loads in the dry season. A second pattern observed in the chart is that loading increases as we move downstream in
the river, as expected in a simulation with no pollution control assumed throughout the city. This pattern is observed
by comparing the multiple bars in each month. The bars corresponding to lower reaches have greater concentrations
of zinc.
When looking a t the e ffects of TWM options in w ater quality, Figure 23 shows a cl ear positive impact in the
reduction of loading fromt he Baseline. TWM A Iternative 1, with emphasis on water supply, presents a c lear
reduction i n 1 oads w hile TWM A Iternative 2, w ith e mphasis i n runoff m anagement, pe rforms e ven be tter i n that
regard. Figure 23 da ta c orresponds t o t he y ear 201 5, but t he s ame t rends w ere obs erved for g enerally all y ears
simulated.
43
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8,000
7,000
1,000
I Los Angeles River 0 \Headflow
I Los Angeles River 5 \Return
Flow Node 2
Los Angeles River 6 \Reach
I Los Angeles River 11 \ Return
Flow Node 9
Los Angeles River 12 \ Reach
Los Angeles River 17 \ Return
Flow Node 12
Los Angeles River 18 \ Reach
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 22. Seasonality of zinc loading in the Los Angeles River for baseline
30,000
LA River 18 \Reach
I Baseline TWMAItl TWMAIt2
Figure 23. Comparison of annual zinc loading in Los Angeles River in 2015 for baseline and total water
management alternatives
44
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Greenhouse Gas Emissions
The third environmental related metric in the analysis corresponds to GHG emissions. Specific GHG emission
estimates exist for imported water in Southern California. These estimates were applied to the amounts of imported
water in each simulation on a per acre-foot of basis. The method use in this study for the estimates of GHG emissions
for all sources consists of the following steps:
Define percentage of the O&M costs (excluding imported water) due to energy
Estimate energy consumption based on costs of energy
Apply region-specific factors of CO2, CH4 and NOX
Make CH4 and NOX conversions to CO2 equivalents
Add CO2 equivalent emissions from imported water (estimated separately)
This method can be applied in any TWM project in the U.S., as long as reasonable assumptions can be made about the
source oft he energy and, more specifically, about the fuel mix used in energy generation. Figure 24 pr esents the
estimates of GHG emissions for the baseline and the TWM alternatives.
30,000,000
25,000,000
ซ 20,000,000
O
u
ง 15,000,000
u
I 10,000,000
5,000,000
0
8,624,161
17,461,531
13,543,885
9,060,011
12,041,637
12,133,875
Reference TWM SI Water Supply TWM S2 Water Quality
I Imported Water Other Sources and Energy Uses
Figure 24. Predicted greenhouse gas emissions over 25 years for the baseline and total water management
alternatives
The emissions presented in Figure 24 indicate that the Baseline is the worst performing alternative, even though the
emissions due to operation of local sources are much higher in the TWM alternatives (maroon bars). The "savings" in
the local supply options for the Baseline are not sufficient to offset the great difference between the alternatives in
terms of the GHG emissions from transporting imported supplies over hundreds of miles.
45
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Financial Results
There are a number of ways and different metrics to compare alternatives in relation to their costs. Financial results
in this TWM analysis included the Net Present Value (NPV) over the 25 years, average unit cost of the supply mix,
and annual operating costs. Figure 25 presents the comparison of the NPV and Table 1 presents the average unit cost
of the supply mix for the simulation period.
Baseline
TWM Alternative 1 TWM Alternative 2
Capital Cost Operating Cost
Figure 25. Net present value cost of baseline and total water management alternatives for simulation period
Table 1. Financial Measures Comparing Alternatives
Alternative
Baseline
TWM Alt 1
TWM Alt 2
Net Present Value
of Capital
($ Millions)
164
877
843
Net Present Value
ofO&M
($ Millions)
6,609
4,774
5,518
Total Net Present
Value
($ Millions)
6,772
5,651
6,362
Average Unit Cost of
Water Supply
S587/AF
S553/AF
S580/AF
Figure 25 and Table 1 show that the capital costs of TWM Alternatives 1 and 2 are very similar with higher operating
costs for TWM Alternative 2, resulting in an overall higher NPV for that alternative. Both TWM alternatives present
lower NPV costs than the baseline. That is due to the fact that imported water cost is the main driving element in the
NPV and total costs of the alternatives simulated. Figure 26 presents the breakup of the annual operating costs for the
alternatives. The total operating costs of the Baseline are the highest of the three alternatives while TWM Alternative
1 is the lowest. Figure 26 shows TWM Alternative 1 ha s the lowest proportion of imported water (51%) while the
Baseline has the highest (80%). On average in the 25 years simulated, TWM Alternative 1's proportion of 49% for
non-imported w ater c osts corresponds to a bout $ 163 m illion pe r y ear. It is th e hi ghest an nual co st o f the t hree
alternatives with the Baseline at $92 million for non-imported water costs and TWM Alternative 2 at $146 million.
Yet, on the total costs, TWM Alternative 1 has the lowest figure due to the high costs of imported supply.
46
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Baseline
20%
D Imported Water
Operating Costs
D Operating Costs Excluding
Imported Water
Total Operating Costs Per Year
Baseline Million $465
TWM Alternative 1 Million $332
TWM Alternative 2 Million $386
Baseline
80%
Figure 26. Annual operating costs of baseline and total water management alternatives
Infrastructure Related Benefits
Another benefit of TWM is reducing or avoiding the need for additional infrastructure. The WEAP model tracks
every flow path in the system so that it is possible to determine the amount of influent reaching HTP, which is the
downstream WWTP for m uch o f the C ity (see F igure 9). This WWTP is w here full se condary t reated water i s
discharged into the ocean. The following benefits could occur from reducing wastewater flows to HTP: (1) reducing
annual operating costs of the treatment plant and discharges into the ocean; (2) delaying or eliminating any future
need to expand the ocean outfall; (3) delaying or eliminating the need for future expansion of the treatment p lant
itself; (4) delaying or eliminating the need for expansion of major inceptor sewers; and (5) reducing the impact of
wastewater discharges on the ocean environment.
For the purposes of this study, flows to HTP were used as a proxy for all the potential benefits of TWM. Figure 27
shows the average monthly inflow (year 2030) into the HTP, the City's largest WWTP. TWM Alternative 2 had a
13% reduction in wastewater flows to HTP from the Baseline, which was accomplished by increased recycled water
for groundwater recharge in the SFV zone. TWM Alternative 1 had a 27% reduction in wastewater flows to HTP
from t he B aseline, due to increased recycled water for groundwater recharge and non-potable us e, a s w ell a s
implementation ofgraywater systems. Deferment of wastewater infrastructure maybe one of the most significant
benefits of TWM because these benefits can occur in urban areas where water supply is not a significant problem.
47
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TWMAItl TWMAIt2
Figure 27. Average potential monthly wastewater flows into Hyperion Treatment Plant for baseline and total
water management alternatives
Another potential infrastructure benefit of TWM is decoupling the water distribution system for fire flows. Fire flows
impose significant peaking requirements for the design of water distribution systems and using r ecycled w ater to
provide fire flow could eliminate the need for additional pumping, storage or pipe sizing. The City is considerably
built out and decoupling the fire flows from the water system would be enormously expensive and likely not provide
net benefits unless a thorough replacement of the potable system is required in the future, i.e., due to infrastructure
replacement needs or catastrophic damage, e.g., earthquake. The infrastructure replacement need is beyond scope of
this report; however, regions with new demand areas or significant replacement p rograms for w ater lines should
consider the evaluation of that TWM option.
Climate Change Scenario Results
To estimate the sensitivity to potential climate change, the Baseline and the TWM alternatives were simulated under a
specific climate change scenario, evaluated by the DWR. DWR conducted several climate change simulations for
their report on State Water P reject Reliability Report (DWR, 2007). The report p resents estimated reductions i n
water deliveries from northern California based on the downscaling of several GCMs and emission scenarios.
Appendix C describes the assumptions and logic behind the hydrology dependent variables. Because the LAA and
MWD water supplies are highly dependent on snowpack, they are very vulnerable to the impacts of climate change.
Although specific analysis for climate change on the LAA has not yet been completed, it was assumed that climate
change would have the same impact (in terms of reduction in supply) as the SWP (as discussed in Appendix C).
48
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Results of the climate change scenario are mostly observed in supply reliability. The result of the analysis was that,
under the Baseline, average annual supply deficits increased by almost 1,500 AFY. Under TWM Alternative 1, there
were still no supply deficits even with climate change. TWM Alternative 2 was also not impacted by climate change.
An interesting result in the climate change scenario is that the NPV of the each of the alternatives under climate
change conditions is higher than the no climate change scenario. Under climate change, the NPV of the alternatives
increases from the values presented in Figure 25 (no climate change) by $2,000,000 to $18,000,000. This is the result
of the reduction in LAA water with the required increases purchases of MWD supplies, which are more expensive per
volume. As demand increases, the reductions in LAA water become more important and the increases in MWD water
are more significant. Over the 25 year simulation, there is sufficient added volume of MWD in the climate change
scenario to have an impact on the NPV. Figure 28 shows the increased MWD annual flows (per year and cumulative)
for all alternatives, when climate change is assumed. In the real system, the MWD supplies are indeed much more
reliable given that MWD's system has much larger storage than the LAA.
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30,000
25,000
20,000
15,000
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.
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I Baseline
Cumulative
I TWM Alt 1
Cumulative
TWM Alt 2
Cumulative
Figure 28. Increased Metropolitan Water District of Southern California imported water supplies in the climate
change scenario for baseline and total water management alternatives
Figure 28 presents how much more MWD water, i.e., expensive water, is purchased under climate change conditions,
but it does not show how much total MWD water is used each simulated year. That is why in the year 2024 there is a
significant increase in MWD water for the TWM Alternatives whereas the baseline shows only a slight increase. Th
is because the baseline is already close to maximum MWD deliveries under no climate change (requiring ov er
326,000 AFY). When climate change is simulated, only an additional 1,700 AFY is available for a total of 328,000
AFY as MWD deliveries "max out" that particular year. For the TWM alternatives, the increases in MWD purchases
are almost 30,000 AFY; these values are nowhere close to the maximum MWD deliveries (92,000 AFY and 178,000
AFY for TWM Alternative 1 and TWM Alternative 2, respectively). When climate change is simulated, the TWM
49
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alternatives do become more dependent on MWD but these alternatives can actually get the additional supply before
reaching the maximum. Figure 28 also shows the cumulative additional MWD over the study years, which causes the
additional NPV.
In climate cha nge s imulations, a better p icture o f p otential impacts can be obtained by running a p robabilistic
analysis. Figure 28 does not present a probabilistic analysis, since it was developed with a direct application of the
hydrology sequence from 1980 to 2003, imposed in demand projections from 2010 to 2033. The WEAP Model could
accommodate a probabilistic run in which the sequence of hydrology could be applied to a single year, and thus
generate an envelope of o utcomes for that given single year. That analysis was beyond the scope of this study, in
which a simple analysis was developed to show one of the potential benefits of TWM regarding climate change.
Earthquake Emergency Scenario Results
This emergency scenario was set up by assuming an earthquake that would significantly disrupt imported supply from
MWD, to the Los Angeles area. The model did not assign specific probabilities for this scenario. The analysis
consisted in selecting one month simulated by WEAP, in the year 2030 (2030 demands) and eliminating the MWD
supply from the supply mix of resources.
The results presented in Figure 29 assume that the MWD supply is interrupted in October of 2030. The seasonality
factor for the month of October (as explained in Appendix B) is equal to 1.22, which means demands are higher than
the average month (for comparison, the highest seasonality factor corresponds to August with 1.59). The baseline
presents a deficit for that month of 27,842 AF but that deficit is much smaller for TWM Alternative 1 and TWM
Alternative 2. The maximum reliability benefits for TWM Alternative 1 come from increased conservation, recycled
water and added graywater use as compared to the Baseline. For TWM Alternative 2, the greatest benefit is also from
increased conservation and recycled water. The supply deficit in the Baseline Alternative is more than four times as
large as the TWM Alternative 1, and more than doubles TWM Alternative 2.
50
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90,000
80,000
Deficit
Imported LAA
Greywater Reused
Rainwater Harvested
Centralized Stormwater
Recharge
I DWUR Beneficially Reused
Recycled Water
I Groundwater
I Conservation
Baseline
TWMAItl TWMAIt2
Figure 29. Water supply mix and supply deficit for emergency scenario for baseline and total water
management alternatives
Case Study Conclusions
The c ase study for LosAngeles clearly showsthe benefits ofTWM, as demonstrated i n T able 2. A 11 ofthe
performance measures, including overall net present value costs, were significantly better for the TWM Alternatives,
compared to the Baseline (which represents the traditional water management approach).
This conclusion will likely not be the case everywhere TWM is evaluated. But this case study can be used to help
water managers establish a credible evaluation framework for analyzing each component of TWM and determine if
the benefits outweigh the additional costs.
Table 2. Comparison of Performance Measures for Baseline and Options
Performance Measure
Water Demand in 2030 (AFY)
Maximum Annual Supply Deficit (AFY)
Average Annual MWD Imports (AFY)
Zinc Loading at Downstream End of Los Angeles River (kg/yr)
Cumulative CO2 Emissions (metric tons)
Average Monthly Wastewater Flows into HTP (MGD)
Supply Deficit in Emergency Scenario (AF/month)
Net Present Value ($ millions)
Baseline
762,700
78,400
135,267
26,569
26,085,692
375
27,840
$6,672
TWM1
655,800
-
32,599
23,788
22,603,896
270
6,680
$5,651
TWM 2
711,400
11,400
62,939
22,089
24,175,512
335
12,860
$6,362
This case study has used a large urban area (Los Angeles) to illustrate the potential benefits of a TWM approach. The
results and conclusions, however, are applicable to smaller areas and to cities with less financial resources than the
City. TWM options are not necessarily more or less cost effective than traditional engineering and planning options,
51
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but it is through the formal evaluation and quantitative analysis that decisions should be made about the merits of the
approach.
Implementation of the TWM alternatives in the City presents the same challenges that would be faced in other cities
and regions, where different agencies have jurisdiction and mandates that are exclusive of a system. In fact one of the
main tenants o f TWM is to breakdown the ba rriers that of ten ex istbe tween the m ultiple agencies and city
departments that have some role in water management.
52
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Chapter 6 Conclusions
This report has illustrated the state of knowledge and practice of TWM. Through the analysis of a real a case study,
the report has demonstrated some of the system-wide benefits that can be achieved by implementation of TWM.
The literature review and desktop analysis have shown that TWM is generally better suited to meet challenges such as
limited fresh water supplies, degradation of receiving water quality, increasing regulatory requirements, flood
management, aging infrastructure, and rising utility costs. However, the implementation of a TWM approach will
require new frameworks for planning, decision-making, design, engineering, and operations that involve more than
one administrative entity.
TWM can be implemented when different service functions of a region (e.g., utilities such as water, wastewater, and
stormwater) integrate planning and project implementation functions. Implementation of the TWM alternatives can
present challenges in most cities and regions, where multiple agencies or departments have different jurisdictions and
mandates. Functional ba rriers ne ed t o be addressed and considered when implementing TWM. Onekeylesson
learned from urba n watersheds implementing T WM i s t hat agencies do no t ha ve t o give up control ov er t he
implementation and operation of projects and facilities. But by collaborating and cooperating on the planning process
and decision-making, new opportunities for better water resources management will likely arise.
Additionally, it is fully recognized that there are currently many regulatory barriers that may impede taking a TWM
approach, such as:
(1) uses of recycled water;
(2) full-scale implementation of graywater systems;
(3) water right issues associated with stormwater capture; and others.
The framework for TWM planning and evaluation presented in this report can be used to objectively determine if the
benefits outweigh changing these regulations.
53
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References
American Waterworks Association Research Foundation (AwwaRF) (1996). "Minutes of Workshop on Total Water
Management." Seattle, WA and Denver, CO: American Water Works Association, August 1996
AwwaRF, (1998). Guidelines for Implementing an Effective Integrated Resource Planning Process. AwwaRF. Project
#920. Prepared by Wade Miller Associates, Inc., West Virginia University, and Tellus Institute.
Baldwin, T., T. Brodeur, R. Cavalieri, C. Ferraro, K. O'Neil, C. Vogel andH. Wilkening (2007). TWM: Florida's
Water F uture 2007. Florida's Water F utureW aterF orum, Orlando, F lorida, September 25 &26, 2007
(http://www.fwea.Org/cmsitems/attachments/9/2WaterForumWhitePaper-TWM.pdf).
City of Los Angeles (2006a) Department of Public Works (DPW), Bureau of Sanitation, and Department of Water
and Power. Prepared by CH:CDM. Integrated Resources Plan, Facilities Plan, Volume 2.
City of Los Angeles (2006b), Department of Public Works (DPW), Bureau of Sanitation, and Department of Water
and Power. Prepared by CH:CDM. Integrated Resources Plan, Facilities Plan, Volume 3.
City of Los Angeles (2006c), Department of Public Works (DPW), Bureau of Sanitation, and Department of Water
and Power. Prepared by CH:CDM. Integrated Resources Plan, Facilities Plan, Volume 4.
City of L os A ngeles (2009), Department of P ublic Works ( DPW), B ureau of S anitation, Watershed P rotection
Division. Water Quality Compliance Master Plan for Urban Runoff
City of Los Angeles, Department of Public Works (DPW) (2010). City of Los Angeles Recycled Water Master Plan -
Draft Site Assessment Technical Memorandum. January 2010, prepared by RMC:CDM. Appendix B.
Grigg, N. S. (1996). Water Resources Management: Principles. Regulations, and Cases. New York: McGraw-Hill,
ISBN10: 007024782X, 544 pp.
Grigg, N. S. (2008). Total Wat er Mana gement: P ractices for a Sustainable F uture. Denver, CO: American Water
Works Association, ISBN 10 1583215506, 308 pp.
Guo, Y. and B. Baetz (2007). Sizing of rainwater storage units for Green Building applications. Journal of Hydrologic
Engineering, 12(2), 197-205.
Hill, T., G. Symmonds and W. Smith (2007). TOTAL WATER MANAGEMENT: RESOURCE CONSERVATION
IN THE FACE OF POPULATION GROWTH AND WATER SCARCITY, Report developed for Global Water.
Lopez, C. E. 2005. "Effectively Manage Stakeholder Involvement in Integrated Resources Planning" Published in
Source Magazine. Vol. 19, No.3. Fall 2005.
Lopez, C. E., A. Magallanes, and D. Cannon. "Systems Modeling for Integrated Planning in the City of Los Angeles:
Using S imulation a s a Tool for Decision Making" Published in WEFTEC'2001, Water Environment Federation
National Conference Proceedings. 2001.
Los Angeles Department of Water and Power (LADWP) (2005). 2005 Urban Water Management Plan. Prepared by
COM.
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McAllister, Donald M. 1995. Evaluation in Environmental Planning. 6th edition. MIT Press. 308 pp.
Mendoza-Espinosa, L., C. E. Lopez and O. Figueroa-Nolasco. "Systems Modeling for the Planning of Grey Water in
New H ousing D evelopments i n the C ity of E nsenada, B aja C alifornia, Mexico." P ublished i n WEFTEC 2006,
Water Environment Federation National Conference Proceedings.
Michaud, W. R. (2009). IWRReport 2009-R-7. Performance Measures to Assess the Benefits of S hared Vision
Planning and Other Collaborative Modeling Processes.
Muniz, A., R. David, G. Pyne and S. M. Trost (1993). Innovation and diversification - the key to our future water
supply. In Water Management i n the ' 90s: A Time for Innovation, A SCE's Wat er Resources P lanning and
Management Division, Seattle, Washington, May 1-5, 1993., pp. 324-327.
Palmer, R., W. Werick, A. MacEwan and A. Woods (1999). "Modeling water resources opportunities, challenges,
and trade-offs: The use of shared vision modeling for negotiation and conflict resolution." Proceedings of the 26th
Annual Water Resources Planning and Management Conference held in Tempe, Arizona, June 6-9, 1999, Ed. Erin
M. Wilson, Reston, VAASCE, 0-7844-0430-5.
Texas Water Development Board. 2005. The T exas Man ual on Rain Waster Harvesting. Third Edition.
(http://www.twdb.state.tx.us/publications/reports/RainwaterHarvestingManual 3rdedition.pdf).
Young, J. (2006). "Manager to Manager ~ Challenges and Benefits of Total Water Management" Journal American
Waterworks Association, Vol. 98, No. 6, p. 32-34, June 2006.
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Appendix A - Cost Assumptions for Case Study
The TWM options used in the desktop analysis case study were programmed in the WEAP model with capital, fixed
O&M and variable O&M estimates. This appendix describes the cost assumptions and sources for all options. The
appendix also includes costs assumptions for sources not related to TWM but included in the model, such as imported
water costs.
Metropolitan Water District's Imported Water Costs
Imported water costs (dollars per AF) were entered in the model as a time series with forecasted projections between
2008 and 2033. These projections are in projected-year dollars, including inflation. Projections for the earlier years
are from MWD (www.mwdh2o .com), while the outer years are based on past historical rates of change. Table A-l
presents the projected rates used in the model, which correspond to MWD's Tier 1 treated water rates.
Table A-l. Projected MWD Unit Cost for Imported Water
Year Cost per AF Year Cost per AF
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
$ 508
$ 579
$ 643
$ 694
$ 746
$ 798
$ 850
$ 901
$ 930
$ 959
$ 988
$ 1,016
$ 1,045
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
$ 1,078
$ 1,112
$ 1,145
$ 1,178
$ 1,211
$ 1,237
$ 1,262
$ 1,287
$ 1,312
$ 1,337
$ 1,363
$ 1,388
$ 1,413
Conservation
The TWM options included in the on c onservation include both, indoor and outdoor conservation measures. The
model used two separate estimates of for the two types of programs:
Indoor conservation: S390/AF
Outdoor conservation: S430/AF
These estimates are very general in nature but based on estimates of total water savings (indoor and outdoor) and
annual costs associated with those savings from other cities including San Diego area (Santa Fe Irrigation District and
Edmond Oklahoma).
Water conservation measures that would result in waster savings between 5% and 10% include: distribution of water
conservation education and awareness m aterial t o customers and in schools; distribution of dye tablet kits with
instructions for detection and correction of 1 eaky toilets; p roviding i nstructionst o customers on p roper s etting
A-l
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adjustments of irrigation controllers; distribution of moisture sensors for use with irrigation controllers; providing
water audits of residential customer properties on request, and target high water using customers.
As part of a planning effort, the City of Edmond Oklahoma conducted a review and analysis of similar conservation
programs throughout the U.S. concluding that these programs could be implemented and administered for $0.20 or
less per gallon per day of water savings. For higher levels of efficiency in water use, the water conservation measures
that would need to be implemented include: providing rebates for installation of dual-flush toilets which have separate
settings for urine and fecal flush; providing rebates for water efficient clothes washers; with a cost to these programs
(implemented and administration) for $0.50 or less per gallon per day of water savings. Applying the costs of these
programs to their expected water efficiency levels resulted in the unit costs presented above.
Wastewater Recycling
Los Angeles has existing reclamation facilities as described in Chapter 5. None of the TWM options e valuated
included the expansion of those reclamation facilities. Some options however, included the expansion of the recycled
water system. The costs for the expansion the system was based on estimates for pipelines and pump stations of sizes
similar to the options included in the analysis (10 MGD or lower).
Estimates were derived using the following costs items for the system:
Pipeline Capital Costs: $15/ft-inch diameter. Assuming 4.5 miles of 20 inch pipeline, pipeline costs are: $7,128,000
Pump Station Capital Costs: $4,060/hp of installed capacity. Assuming a medium size pump station of 1,980 hp, the
capital costs are $7,985,000
These di mensions of the system assum ed a 6 MGD expansion. The uni t c ost pe r MGD of ins tailed c apacity
expansion of the system is then:
$15,113,000/6 MGD = $2,518,700/MGD
This capital unit cost was applied in the model to expansions of recycled water (distribution only).
Fixed O&M costs for this system were assumed at 1% of capital cost, and variable O&M costs were obtained from
the City of Los Angeles Recycled Water Master Plan - Draft Site Assessment Technical Memorandum (City of Los
Angeles DPW, 2010). This report, specifically for Los Angeles, reports variable O&M costs equal to $179/AF, for
the TWRP. This variable cost includes the costs of treatment in addition to the costs of pumping to demands.
Dry-Weather Urban Runoff Capture and Reuse
This TWM option includes two main components: diversion from the stormwater system, and treatment for beneficial
use. The diversion from the stormwater system can be to the wastewater co llection system or to the dedicated
treatment facility, but its costs are assumed to be the same (regardless of the fate of the DWUR).
Diversions
The capital cost for the diversion structures was obtained from the City's IRP (City of Los Angeles, 2006a, 2006b,
2006c). A unit cost of $1,855,000/MGD was used for this project, based on the costs used in cited report.
Fixed O&M cos ts a re a ssumed at 2 % of c apital, and v ariable c osts w ere e stimated a t $64 /AF f or t he pumping
required.
A-2
-------
Dedicated Treatment
The facility assumed for the estimates of dedicated treatment for DWUR includes the processes of dissolved air
flotation and microfiltration, and the associated pumping with those processes. This facility is similar an existing
facility in the City of Santa Monica.
Capital costs were obtained from the City's IRP (City of Los Angeles, 2006 a, 2006b, 2006 c) for the Wastewater
Program and updated. The unit cost is $2,810,000/MGD of capacity installed.
Variable O&M costs are assumed at 1 % of capital costs and variable O&M are based on the treatment processes
included and ba sed on t he City of L os A ngeles I ntegrated Plan for t he W astewater P rogram, and correspond t o
S128/AF. This estimate assumes the system is shut down during rain events.
Graywater
Graywater cost estimates are based on information from a vendor for at ypical domestic system. The size of the
system assumed would provide estimated savings of 1,200 to 1,300 gallons per month.
The capital cost of the system is $1,369 pe r unit. The fixed O&M costs are assumed to be 1 % of the capital and
variable costs are $0.15 per AF.
Rain Water Harvesting
Rain Water harvest sy stem cos t es timates ar e ba sed on information f rom t he Texas M anual o n Rain Waster
Harvesting (Texas Water Development Board, 2005) for a typical domestic system. Estimates were updated from the
2005 data included in the manual. The size of the system assumed for cost estimates is for an average house of 1,300
sq.ft.
Capital costs for the system are $1,909 per system. The fixed O&M costs are assumed to be 1% of the capital and
variable costs are $0.15 per AF.
Water Recycling Through Groundwater Recharge
Significant work exists on this option with several reports available from the City. The data used for this study is
based on the "City of Los Angeles Recycled Water Master Plan - Draft Site Assessment Technical Memorandum"
(City of Los Angeles DPW, 2010).
The capital cost assumes advanced wastewater treatment including reverse osmosis. The unit cost for capital is equal
to $6,758,000/MGD of capacity installed.
The fixed O&M costs are based on a 60 MGD facility of tertiary treatment with 32 MGD facility for advance water
treatment with RO. The annual estimates correspond to $11,218,000.
Variable costs for treatment and pumping to the recharge facilities are $179 per AF.
A-3
-------
Centralized and Decentralized Stormwater Recharge
Centralized System
Stormwater recharge facilities costs were obtained from estimates in the City of Los Angeles IRP for a system in the
SFV zone. Capacity was estimated at 245 MGD for 26 days (dictated by 100 inch pipeline diameter). There are no
dimensions given for the recharge facilities as it is assumed existing recharge facilities would be used.
The capital cost for a facility with a yield of 245 MGD is equal to $87 million. Fixed O&M costs are assumed at 1%
of capital. Since variable costs are not provided in the document for this facility, variable costs were assumed to be
the same as a decentralized system (see below).
Decentralized System
Stormwater recharge f acilities cos ts w ere obtained from various e stimates of systems in the C ity from project
proposals submitted as part of the City's "Proposition O "(proposition O i s a ballot initiative that was voted by the
citizens of Los Angeles that made city funds available for environmental projects proposed by government agencies
and citizen groups). Various capacities and costs were compiled and an average cost per acre of project was derived.
The types of projects ranged from neighborhood recharge in vacant lots, to neighborhood recharge in parks and open
space, and recharge in abandoned alleys. The acreage of projects ranged from 15 acres to over 340 acres.
The unit capital cost of this option is $1,161,000/Acre. Fixed costs were also based on an acreage basis and were
equal to $9,800/acre. Variable costs are estimated at $81/AF, which means that the cost will vary depending on the
volumes managed.
Expansion of Groundwater Pumping Facilities
In addition to the TWM opt ions described above, costs estimates were included in the model for expansion of
groundwater pumping and delivery capacity. This expansion i s ne cessary t o ut ilize groundwater recharged under
some of the TWM options. Not expanding the groundwater wells would result in not being able to utilize the
recharged water since the groundwater system in Los Angeles is practically operated at capacity today.
The cost estimates were based on estimates from other studies in California, in the Los Angeles area. Expansion of
the groundwater wells assumes: land acquisition, production well (assumed 800 ft deep), connection to distribution
system, water quality sampling, and pump station. The well estimate does not include treatment costs.
The unit capital cost of the expansion is $1,819,000/MGD. Fixed O&M costs are assumed at 1 % of capital and
variable costs are assumed at $200/AF.
A-4
-------
Appendix B - Rainfall and Stormwater Calculations
The WEAP model is programmed to compute the system-level rainwater volumes and routing along various user-
defined pathways on a monthly basis. The model is structured and parameterized to be able to track the amount of
rainfall that infiltrates into the ground and the amount that becomes urban runoff. The model also includes
parameters and decision variables to allocate rainwater for direct capture (e.g., "harvesting" in cisterns and rain
barrels) and for groundwater recharge - both "centralized" and "decentralized" cases. The approach and calculations
for rainfall and stormwater in the model are described below.
Demand Zones, Rainfall Data, and Rainfall Volumes
In the model, the City has been divided into four "demand zones" (SFV, Central, West, and SP). Each demand zone
is associated with a physical area in the city, and thus has a surface area attribute (in acres). Historic monthly rainfall
data was obtained from a gauge for each of the demand zones. The model runs a 23 year simulation (2010-2033), and
uses rainfall data from the period of record from 1980-2003. The rainfall data used in the model is presented in Table
B-l at the end of this appendix.
The total monthly volume of rainfall, V, to be accounted for and routed in each demand zone is calculated as the
product of the rainfall depth and the zone surface area:
V = Rain(month) x Area(zone)
The routing pathways for this rainfall volume are depicted in the schematic in Figure B-l. Monthly rainfall generally
becomes either infiltration (to groundwater) or urban runoff. The urban runoff can be routed as "rain harvest",
"centralized stormwater recharge", or "conventional stormwater." The calculation and routing of these flows are
described below.
Rainfall
Volume
Figure B-l: Schematic Diagram of Rainfall Routing
Rainfall Runoff and Infiltration
The routing of monthly rainfall volumes as infiltration and runoff can generally be specified by the percentages
flowing as infiltration and runoff:
Infiltration = Vx %Inf
Runoff = Vx %RO
Rainfall accounting has been adjusted according to the approach employed for simplistic groundwater basin tracking.
In this study, data on the "natural groundwater recharge" was not available. As such, it was not possible to model
B-l
-------
based on actual inflows, outflows, and storage in the groundwater. Instead, the model demonstrates the benefits of
storing water by recharging the groundwater basin - which in the model is termed "banked" storage.
For this reason, the model only tracks the city's efforts at active recharge of water into the basins (for the 'natural
recharge' the model assumes that each year the amount of groundwater that Los Angeles is entitled to is naturally
infiltrated and then pumped by the city, i.e., IN=OUT). Monthly inflows are assumed to match the seasonal pumping
demands; but the model does not track the exact amount of natural inflow to the basin, only the amount to cover Los
Angeles' "normal" groundwater demands.
For infiltration, there are two types: "normal" infiltration, i.e., from the pervious areas of the demand zones, according
to the runoff coefficients, and the infiltration that takes place due to "decentralized stormwater recharge" (see Section
5.3.7 in the main body of the report). Since the model is only tracking "banked" water in the groundwater basin, it
only needs to count the water that infiltrates from the "decentralized" stormwater recharge system. It is assumed that
the "normal infiltration" is included in the natural groundwater recharge (and not explicitly tracked).
These assumptions about groundwater require making adjustments to the rainfall depths and the routing percentages
for Infiltration and Runoff. The adjustments apply a correction that separates the decentralized amounts from the
other infiltration amounts. The term "infiltration" really reflects an effective infiltration in that it is assumed to
account for losses.
The primary assumptions are that:
Volume(rain) = Area * Precipitation
Volume(rain) = Infiltration + Runoff (and "infiltration" accounts for losses, as a percentage in WEAP)
The total runoff volume is the same, before and after correction
The modeled infiltration volume must include only the volume from the decentralized stormwater areas
From these assumptions and the definition and mass balance equations around the urban catchment, the correction
factors are derived for the three components:
AdjVolume(rain) = Volume(rain) xfactorRain
factorRain = [(%Areapx Cp) + (%Area1 x C,) + (%Areadx C^J + [%Areadx (1 -
%Inf(Adj) = %Area,_K(l-C^
factorRain
%RO(Adj) = [("/oArea^x CJ + (%Area,_x C,) + (%Area,x CJ7
factorRain
Where:
AdjVolume(rain) = Adjusted rain volume (monthly)
Volume(rain) = Normal rain volume (monthly)
B-2
-------
factorRain = Correction factor for rain volume
%Areap = Percent of demand zone area that is pervious surface
%Areaj = Percent of demand zone area that is impervious surface
%Aread = Percent o f d emand zone ar ea t hat i s de dicated t o "decentralized
stormwater recharge" (user defined, decision variable)
Cp = Runoff coefficient for pervious surface
Q = Runoff coefficient for impervious surface
Cd = Runoff coefficient for decentralized stormwater recharge surfaces
These adjusted factors get applied as system parameters in WEAP. The C values used in the WEAP model were
obtained and simplified from current TMDL models in Los Angeles. The "factorRain" term is applied to the rainfall
data series, and the two adjusted routing percentages are applied as the routing parameters for each demand zone's
catchment node flow pathways.
The runoff and infiltration volumes determined from the above parameters are then routed in WEAP as described in
the following sections.
Figure B-2 shows a simple schematic of an urban watershed with its area and runoff parameters and flow routes.
Rain
Decentralized recharge
(swales, ponds, etc)
De-Central
Stormwater
Divert to GW
(Centralized Recharge)
Stormwater
(to receiving body)
Figure B-2: Simple Schematic of Urban Watershed
B-3
-------
WEAP System Schematic for Rainfall and Stormwater Components
Figure B-3 presents the model components as used in the WEAP model for Los Angeles. These components include
an urban catchment, an urban node, two dummy demand nodes, a groundwater basin node, an outdoor demand node,
a receiving water body, and the various linking pathways. The components are referred to and defined in following
sections.
Outdoor Demand
[demand node]
Urban Node
[dummy reservoir node]
Urban Catchment
[catchment node]
Infiltration
Dummy Runoff
[demand node]
Centralized stormwater recharge
GW Basin
[groundwater node]
Dummy Groundwater
[demand node]
Receiving Body
Figure B-3: WEAP Schematic for Rainfall and Stormwater Components
Urban Wet-Weather Runoff
The urban wet weather runoff is the volume calculated using the "%RO(Adj)" term above multiplied by the total
rainfall v olume i n the de mand z one' s catchment nod e. This v olume i s then r outed t o t he d emand z one' s " Urban
Node" - which is a dummy node in the model used only for calculation purposes (see Figure B-3). In WEAP, the
Urban Node is a zero-storage reservoir where the sum of all inflows equals the sum of all out flows. This approach is
used to r oute the urban r unoff through t hree p athways: r ain ha rvesting, c entralized g roundwater recharge, a nd
conventional stormwater (each described in sections be low). WEAP routes the water through the three pathways
according to:
Runoff availability, i.e., all inflow to Urban Node must be routed
Water demand, according to the demand priorities
Flow path constraints
Rain Harvesting
Rain harvesting is modeled in WEAP as a transmission link from the (dummy) Urban Node to the Outdoor Demand
node, in each demand zone (see Figure B -3). O utdoor demands are specified in the model as the second highest
priority demand category (after Indoor Demands), and thus of the available urban runoff volumes in each month,
WEAP will first route water along the rain harvest pathway.
A monthly flow c onstraint i s applied to the r ain h arvest p athway i n o rder t o 1 imit r unoff r outing a ccording t o
assumptions about the size and operations of the rain harvesting system.
B-4
-------
The monthly constraint on the rain harvesting transmission link is defined as:
MaxVolume(rainHarvest) = OnOff(rainHarvest) x CaptureArea x Depth(rain) x %EffCapture
Where:
MaxVolume (rainHarvest) = Monthly constraint on rain harvest pathway
OnOff(rainHarvest) = Decision variable "switch" for TWM option
CaptureArea = Decision variable of roof area dedicated to rain capture [Ac]
Depth(rain) = Monthly rainfall depth [in]
%EffCapture = Percentage of total rainfall volume that can be captured and used
(based on rainfall patterns, storage volumes, demand and use
rates, etc)
The typical system assumed in the model was one cubic meter (1000 liters), which results in a supply of 10 to 15 days
for irrigation. This means that completely full system would be depleted after 10 to 15 days if no rain re-fills the
system. The sizing (assumed size) of the system was based on considerations of reliability vs. practical realities to fit
a system in a typical residence. The 1,000 liters system was selected as a "middle of the range" size for reliabilities as
reported by Guo and Baetz (2007).
Centralized Stormwater Recharge of Groundwater
The centralized Stormwater recharge TWM option is modeled in WEAP as a transmission link between the (dummy)
Urban Node and a "Dummy GW" node in each demand zone (see Figure B-3). The dummy groundwater node is used
to drive water recharge into the groundwater basins (WEAP does not have a "demand" parameter for groundwater
basins). The dummy groundwater node is given and arbitrarily high demand value, which will force WEAP to route
water into the basin through this pathway. Monthly flows are limited however by a constraint on the transmission
link, which represents the centralized Stormwater recharge facilities capacity. The dummy groundwater demand node
is given a low demand priority (so that WEAP satisfies other, "real" demands in the system first).
The monthly constraint on the centralized Stormwater recharge transmission link is defined as:
MaxVolume(centralSW) = OnOff(centralSW) x Capacity(centralSW)
Where:
MaxVolume (centralSW) = Monthly constraint on centralized Stormwater recharge pathway
OnOff(centralSW) = Decision variable "switch" for TWM option
Capacity (centralSW) = Decision variable capacity for facilities [MOD]
Conventional Stormwater
The default flow for urban runoff in the model is through the city's conventional Stormwater system. Excess urban
runoff that does not get captured and used as rainwater harvesting or centralized Stormwater recharge flows through
the conventional Stormwater system. The conventional system is modeled in WEAP as a transmission link between
the (dummy) Urban Node and a "Dummy Runoff node in each demand zone (see Figure B-3). Similar to the dummy
demand node in the centralized Stormwater recharge pathway described above, the dummy runoff node has an
arbitrarily high demand value - to drive WEAP to route urban runoff through the transmission link. The dummy
B-5
-------
runoff demand nodes have the lowest demand priority in the system, and represent the "default" routing path for
urban runoff- WEAP will utilize all other pathways first in order to meet demands up to facilities capacities. For this
study, there is no capacity constraint placed on the stormwater transmission link.
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
1980
1980
1980
1980
1980
1980
1980
1980
1980
1980
1980
1980
1981
1981
1981
1981
1981
1981
1981
1981
1981
1981
1981
1981
1982
1982
1982
1982
1982
1982
1982
1982
1982
1982
2010
2010
2010
2010
2010
2010
2010
2010
2010
2010
2010
2010
2011
2011
2011
2011
2011
2011
2011
2011
2011
2011
2011
2011
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
7.5
14.4
3.8
0.4
0.1
0.0
0.0
0.0
0.0
0.0
0.0
1.1
2.3
2.1
5.0
0.5
0.0
0.0
0.0
0.0
0.0
0.5
2.6
0.6
3.1
0.6
5.7
2.2
0.1
0.1
0.0
0.0
0.7
0.3
7.5
12.8
4.8
0.3
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.9
2.0
1.5
4.1
0.5
0.0
0.0
0.0
0.0
0.0
0.5
1.8
0.5
2.2
0.7
3.5
1.4
0.1
0.0
0.0
0.0
0.8
0.2
7.0
9.1
3.7
0.2
0.1
0.0
0.0
0.0
0.0
0.0
0.0
1.6
1.5
1.6
3.2
0.5
0.0
0.0
0.0
0.0
0.1
0.4
2.6
1.5
2.8
0.7
3.4
1.6
0.1
0.0
0.0
0.0
0.8
0.2
7.2
9.4
2.9
0.3
0.1
0.0
0.0
0.0
0.0
0.0
0.0
1.5
1.9
1.6
3.4
0.3
0.0
0.0
0.0
0.0
0.1
0.6
2.4
1.0
1.9
0.2
3.1
0.8
0.2
0.0
0.0
0.0
0.4
0.2
B-6
-------
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
1982
1982
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1983
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1984
1985
1985
1985
1985
1985
1985
1985
1985
1985
1985
1985
1985
2012
2012
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2014
2014
2014
2014
2014
2014
2014
2014
2014
2014
2014
2014
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
6.6
1.2
7.3
4.8
12.4
3.3
0.0
0.0
0.0
1.3
1.2
2.2
2.6
3.5
0.1
0.1
0.1
0.4
0.0
0.0
0.0
0.1
0.2
0.2
2.3
6.1
0.8
1.0
1.0
0.0
0.0
0.0
0.1
0.0
0.1
0.3
4.9
1.0
4.4
1.1
6.5
4.4
8.4
5.2
0.4
0.0
0.0
0.8
2.0
0.8
2.5
3.2
0.2
0.0
0.3
0.7
0.0
0.0
0.0
0.4
0.2
0.2
1.4
5.5
0.7
2.8
1.3
0.0
0.2
0.0
0.0
0.0
0.2
0.4
2.9
0.3
3.5
0.7
5.3
5.6
6.4
3.2
0.0
0.0
0.0
1.3
1.9
0.9
2.7
2.1
0.4
0.0
0.1
1.2
0.0
0.0
0.0
0.3
0.1
0.3
1.2
4.2
0.7
1.9
0.7
0.0
0.2
0.0
0.0
0.0
0.3
0.4
4.8
0.4
3.1
0.9
3.0
4.2
8.8
2.3
0.2
0.0
0.0
0.6
1.3
1.4
2.9
2.0
0.3
0.0
0.1
1.1
0.0
0.0
0.1
0.1
0.2
0.4
1.2
5.2
0.9
1.6
0.6
0.0
0.2
0.0
0.0
0.0
0.2
0.1
4.2
0.3
B-7
-------
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
1986
1986
1986
1986
1986
1986
1986
1986
1986
1986
1986
1986
1987
1987
1987
1987
1987
1987
1987
1987
1987
1987
1987
1987
1988
1988
1988
1988
1988
1988
1988
1988
1988
1988
1988
1988
1989
1989
2016
2016
2016
2016
2016
2016
2016
2016
2016
2016
2016
2016
2017
2017
2017
2017
2017
2017
2017
2017
2017
2017
2017
2017
2018
2018
2018
2018
2018
2018
2018
2018
2018
2018
2018
2018
2019
2019
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
3.1
5.9
5.2
0.0
0.0
0.0
0.0
0.0
0.6
1.1
1.3
0.3
1.4
0.7
1.3
0.1
0.0
0.0
0.0
0.0
0.0
5.9
1.2
4.0
2.5
2.2
0.2
4.6
0.0
0.0
0.0
0.0
0.2
0.0
0.8
4.4
0.3
2.2
2.2
6.1
5.3
0.5
0.0
0.0
0.2
0.0
2.0
0.5
0.9
0.4
1.4
1.2
1.0
0.1
0.0
0.1
0.0
0.0
0.1
2.4
1.1
1.8
1.7
1.7
0.3
3.4
0.0
0.0
0.0
0.1
0.0
0.0
0.7
3.8
0.7
1.9
2.3
5.4
4.9
0.3
0.0
0.0
0.1
0.0
1.4
0.1
1.1
0.3
1.3
0.6
0.9
0.0
0.0
0.1
0.1
0.0
0.1
1.7
0.6
1.8
1.6
1.8
0.1
1.1
0.0
0.0
0.0
0.0
0.1
0.0
0.7
2.5
0.6
1.7
1.9
5.0
2.7
0.4
0.0
0.0
0.2
0.0
1.4
0.4
1.1
0.4
1.9
1.4
0.6
0.1
0.0
0.1
0.1
0.1
0.0
1.6
0.6
1.8
1.7
1.1
0.0
1.3
0.0
0.0
0.0
0.0
0.0
0.0
0.8
3.2
0.4
0.9
B-8
-------
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
1989
1989
1989
1989
1989
1989
1989
1989
1989
1989
1990
1990
1990
1990
1990
1990
1990
1990
1990
1990
1990
1990
1991
1991
1991
1991
1991
1991
1991
1991
1991
1991
1991
1991
1992
1992
1992
1992
2019
2019
2019
2019
2019
2019
2019
2019
2019
2019
2020
2020
2020
2020
2020
2020
2020
2020
2020
2020
2020
2020
2021
2021
2021
2021
2021
2021
2021
2021
2021
2021
2021
2021
2022
2022
2022
2022
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
0.6
0.0
0.0
0.0
0.0
0.0
0.4
0.7
0.4
0.0
2.5
2.7
0.3
0.3
0.7
0.0
0.0
0.1
0.0
0.0
0.4
0.1
1.7
3.6
8.0
0.0
0.0
0.0
0.1
0.0
0.0
0.4
0.0
5.8
2.6
16.0
8.5
0.2
0.8
0.0
0.1
0.0
0.0
0.0
0.4
0.4
0.3
0.0
1.2
3.1
0.2
0.6
1.2
0.0
0.0
0.0
0.0
0.0
0.2
0.0
1.2
0.0
5.9
0.0
0.0
0.0
0.1
0.0
0.1
0.4
0.0
3.2
1.7
8.0
7.1
0.3
0.9
0.0
0.0
0.0
0.0
0.0
0.3
0.3
0.4
0.0
1.2
2.6
0.1
0.3
0.8
0.0
0.0
0.0
0.0
0.0
0.1
0.0
1.4
2.5
4.0
0.0
0.0
0.0
0.2
0.0
0.1
0.1
0.0
2.9
1.6
4.7
5.1
0.2
0.8
0.0
0.0
0.0
0.0
0.0
0.3
0.5
0.1
0.0
1.6
2.1
0.1
0.5
1.2
0.0
0.0
0.0
0.0
0.0
0.2
0.0
1.4
3.4
4.9
0.1
0.0
0.0
0.1
0.0
0.0
0.1
0.1
2.1
1.5
4.5
5.3
0.0
B-9
-------
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
1992
1992
1992
1992
1992
1992
1992
1992
1993
1993
1993
1993
1993
1993
1993
1993
1993
1993
1993
1993
1994
1994
1994
1994
1994
1994
1994
1994
1994
1994
1994
1994
1995
1995
1995
1995
1995
1995
2022
2022
2022
2022
2022
2022
2022
2022
2023
2023
2023
2023
2023
2023
2023
2023
2023
2023
2023
2023
2024
2024
2024
2024
2024
2024
2024
2024
2024
2024
2024
2024
2025
2025
2025
2025
2025
2025
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
0.1
0.0
0.1
0.0
0.0
0.0
0.0
7.7
12.6
9.8
4.1
0.0
0.0
0.5
0.0
0.0
0.0
0.5
0.7
1.2
0.5
4.6
1.8
1.3
0.4
0.0
0.0
0.0
0.0
0.6
0.8
1.1
16.8
1.6
7.4
0.9
0.3
0.5
0.0
0.0
0.1
0.0
0.0
0.7
0.0
4.7
11.8
6.6
2.7
0.0
0.0
0.8
0.0
0.0
0.0
0.2
0.7
0.8
0.3
3.2
1.9
0.8
0.3
0.0
0.0
0.0
0.0
0.2
0.6
1.4
12.6
1.3
7.0
0.6
0.2
0.6
0.0
0.0
0.3
0.0
0.0
0.5
0.0
4.2
10.6
5.5
1.8
0.0
0.0
0.7
0.0
0.0
0.0
0.1
0.9
1.0
0.3
4.4
1.0
0.4
0.1
0.0
0.0
0.0
0.0
0.1
0.7
1.1
12.7
0.6
5.7
0.7
0.6
0.6
0.0
0.0
0.1
0.0
0.0
0.5
0.0
5.0
9.1
5.5
2.0
0.0
0.0
0.9
0.0
0.0
0.0
0.0
0.9
0.8
0.3
5.2
1.3
0.4
0.2
0.0
0.0
0.0
0.0
0.1
0.4
0.5
12.8
0.5
5.2
0.5
0.0
0.5
B-10
-------
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
1995
1995
1995
1995
1995
1995
1996
1996
1996
1996
1996
1996
1996
1996
1996
1996
1996
1996
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1998
1998
1998
1998
1998
1998
1998
1998
2025
2025
2025
2025
2025
2025
2026
2026
2026
2026
2026
2026
2026
2026
2026
2026
2026
2026
2027
2027
2027
2027
2027
2027
2027
2027
2027
2027
2027
2027
2028
2028
2028
2028
2028
2028
2028
2028
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
0.2
0.0
0.0
0.0
0.1
1.5
1.8
4.1
2.6
0.3
0.0
0.0
0.0
0.0
0.0
1.3
1.6
5.6
4.6
0.3
0.0
0.0
0.0
0.0
0.0
0.0
0.4
0.0
3.1
5.7
3.1
18.0
3.9
1.9
4.1
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.1
1.3
3.2
4.9
2.2
0.7
0.0
0.0
0.0
0.0
0.0
1.1
1.6
4.1
5.6
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.5
0.0
2.1
2.5
4.1
13.7
4.1
1.0
3.1
0.1
0.0
0.0
0.1
0.0
0.0
0.0
0.1
2.2
1.9
4.2
1.4
0.4
0.1
0.0
0.0
0.0
0.0
1.5
1.9
4.7
5.1
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.3
0.0
2.7
3.9
3.7
13.8
3.4
1.0
2.5
0.1
0.0
0.0
0.1
0.0
0.0
0.0
0.0
2.0
1.8
4.4
1.3
0.4
0.0
0.0
0.0
0.0
0.0
1.5
1.8
4.1
6.2
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.5
0.0
2.5
3.7
3.0
12.1
4.8
1.5
1.7
0.0
0.0
0.0
B-ll
-------
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
1998
1998
1998
1998
1999
1999
1999
1999
1999
1999
1999
1999
1999
1999
1999
1999
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2001
2001
2001
2001
2001
2001
2001
2001
2001
2001
2028
2028
2028
2028
2029
2029
2029
2029
2029
2029
2029
2029
2029
2029
2029
2029
2030
2030
2030
2030
2030
2030
2030
2030
2030
2030
2030
2030
2031
2031
2031
2031
2031
2031
2031
2031
2031
2031
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
0.1
0.0
1.4
0.4
1.4
0.4
2.0
2.6
0.0
0.7
0.0
0.0
0.0
0.0
0.5
0.3
1.2
6.4
2.0
2.7
0.0
0.0
0.0
0.1
0.1
0.0
0.0
0.0
6.6
9.8
3.4
1.1
0.0
0.0
0.0
0.0
0.0
0.2
0.0
0.0
1.3
0.5
1.9
0.6
1.2
2.6
0.0
0.0
0.0
0.0
0.0
0.0
0.4
0.4
0.9
5.5
2.8
1.5
0.0
0.0
0.0
0.1
0.2
1.0
0.0
0.0
5.6
8.9
1.2
1.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
1.9
0.7
1.2
0.5
2.1
2.2
0.0
0.6
0.0
0.0
0.0
0.0
0.3
0.0
0.9
4.7
2.4
1.9
0.0
0.0
0.0
0.0
0.0
1.1
0.0
0.0
4.7
7.3
1.3
1.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.4
0.6
1.5
0.4
1.8
2.3
0.1
0.5
0.1
0.0
0.0
0.0
0.2
0.1
0.5
2.9
1.7
1.2
0.0
0.0
0.0
0.0
0.0
2.3
0.0
0.0
2.1
5.8
0.3
0.4
0.0
0.0
0.0
0.0
0.0
0.0
B-12
-------
Table B-l Historic Rainfall Data for Los Angeles Demand Zones
[in/month]
Historic Simulation
Year Year Month
2001
2001
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2002
2003
2003
2003
2003
2003
2003
2003
2003
2003
2003
2003
2003
2031
2031
2032
2032
2032
2032
2032
2032
2032
2032
2032
2032
2032
2032
2033
2033
2033
2033
2033
2033
2033
2033
2033
2033
2033
2033
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Demand Zone
San
Fernando Central
Valley City Westside San Pedro
1.7
2.1
0.7
0.1
0.1
0.0
0.1
0.0
0.0
0.0
0.1
0.0
2.2
3.2
0.0
7.8
2.7
1.7
2.0
0.0
0.0
0.0
0.0
0.0
0.3
1.5
1.4
1.4
0.8
0.3
0.3
0.1
0.1
0.0
0.0
0.0
0.0
0.1
2.4
3.3
0.0
4.6
4.3
0.7
1.0
0.0
0.0
0.0
0.0
0.5
0.8
1.4
1.3
1.3
0.7
0.4
0.3
0.0
0.1
0.1
0.0
0.0
0.1
0.1
1.6
1.8
0.0
3.8
1.7
0.5
1.0
0.0
0.0
0.0
0.0
0.7
0.8
1.1
1.0
0.6
0.3
0.1
0.1
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.5
1.5
0.0
3.8
1.7
0.4
1.7
0.1
0.3
0.0
0.0
0.1
0.3
1.3
B-13
-------
Appendix C - Hydrology and Imported Supply Assumptions
The WEAP model is programmed to introduce hydrology-related variability on some of its variables. In addition to
computing the sy stem-level r ainwater v olumes a nd stormwater routing described i n A ppendix B, some v ariables
include fluctuations above and below a r eference value depending on hydrology. The approach for hydrologic
variability (for non-rainfall variables) in the model is described below. Variables described in this appendix include:
Water Demands
MWD Imported Water Supply (with and without climate change)
LAA Water Supply (with and without climate change)
Period of Record
Data was collected for all the variables that depend on hydrology. MWD delivery information was available from
1922 to 2004, LAA was available from 1978 to 2008, while precipitation data was available for about a century. Out
of the three data sets, the limiting one was the LAA. This data set, however, was sufficiently long to be used in the
WEAP model, given that the model only needed 25 years. The period of record was then established as the period
between 1978 and 2003. Once the record was established, a check was made of the statistics and periods included in
the period to make sure that a drought of significance was included in the model. This was confirmed since the data
includes a drought period of the late 1980's and early 1990's.
Demands
Demands, and specifically outdoor demands, are highly correlated to weather. ET dictates irrigation demands and ET
is related to weather. Hot and dry years present higher ET and are therefore higher in water demand. Demands were
varied by hydrology in two different scales: monthly and annual. For monthly demand factors real data was used and
the factors developed are presented below, in Table C-l.
Table C-l. Monthly Demand Factors
January
February
March
April
May
June
July
August
September
October
November
December
0.59
0.44
0.47
0.69
1.00
1.32
1.53
1.59
1.47
1.22
0.95
0.72
Demands were also varied annually based on data on demand over time, corrected by the demand growth not related
to weather. Figure 15 shows how demands vary not only seasonally, but also on a year-to-year basis in addition to
the demand increase due to population growth. Figure 15 shows how demand increases over time, but on a year-to-
C-l
-------
year basis there are ups and downs due to hydrology. Those increases and decreases over and above the average
forecasted demand are due to the hydrology factors applied to the model, presented in Table C-2.
Metropolitan Water District of Southern California Supply
As explained in Chapter 5, MWD receives water from two main sources: the SWP (sources in the Sacramento San
Joaquin Bay Delta) and the Colorado River. MWD system includes significant surface storage but their supplies are
subject to variability due to demand and some shortages do oc cur during extended periods of drought (or pumping
restrictions in the Bay Delta). MWD has modeled their system and projected shortages based on the different
hydrology type years. The WEAP model used their predictions for hydrology types 19801 o 2003 (the period of
record in the WEAP model).
MWD projections are projections of percent shortages. So a baseline flow is needed to apply the percent reductions.
The baseline in the WEAP model was established after research on likely maximum delivery levels. In their UWMP,
the city presents historical data of MWD water purchases. The maximum flow purchased by the city from MWD was
approximately 450 MOD. Additionally, the UWMP presents projections of demand and supply, and for 2030, the
maximum level of MWD purchases assumed (forecasted) is also 450 MGD. The WEAP model used this annual rate
as the basis to apply the percent shortages in Table C-2, which presents the shortages with and without climate
change.
Los Angeles Aqueduct
The Los Angeles aqueduct brings high volumes of water to Los Angeles from the California sierras as explained in
Chapter 5. Actual data on LAA water is available and was used in the WEAP model. These data are presented in
Table C-2.
The hydrology that impacts the source of the LAA is similar to the hydrology of the SWP. Table C-2 presents "Table
A" delivery reductions with and without climate change. "Table A contractors" are users of B ay Delta water in the
California central valley and in southern California. "Table A" is the name of the delivery schedule established for
the users of the SWP (contractors). Given that the hydrology of the SWP and the LAA water is similar, Table A
deliveries (DWR, 2007) were used to calculate the reductions that could be observed during climate change. The
values for LAA flows, and the percent of maximum estimated are presented in Table C-2.
C-2
-------
Table C-2. Hydrology Dependent Variable Time Series used in WEAP model
Year
State Water Project Table A
Deliveries (% of contract)
Los Angeles
Aqueduct Percent
Metropolitan Water District of Los Angeles Available Of Non
Southern California Supply Aqueduct Annual Climate Change
Cutbacks (%) Deliveries Basis
Without Climate With Climate Without Climate With Climate Without Climate With Climate
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Change
94
74
94
62
100
94
100
73
69
55
10
77
5
18
27
85
55
94
87
78
95
100
80
24
50
69
Change (PCM-A2)
94
67
94
52
100
94
100
59
79
41
15
77
4
15
25
86
33
94
89
80
95
99
78
15
45
69
Change
0
0
0
0
0
0
0
0
0
0
25
0
30
20
20
0
0
0
0
0
0
0
0
20
0
0
Change (PCM-A2)
0
0
0
0
0
0
0
0
0
10
25
0
30
25
20
0
20
0
0
0
0
0
0
25
10
0
Change
472,161
492,669
514,546
465,083
482,970
518,511
516,337
496,312
515,095
428,085
360,230
274,457
106,746
180,853
176,919
288,538
132,530
443,538
421,800
435,624
466,836
309,037
255,183
266,923
179,338
251,942
Change (PCM-A2)
100%
91%
100%
84%
100%
100%
100%
81%
100%
75%
100%
100%
80%
83%
93%
100%
60%
100%
100%
100%
100%
99%
98%
63%
90%
100%
Demand Annual
Factors
With and Without
Climate Change
1.017
1.035
1.010
1.020
0.871
0.965
1.046
1.010
1.029
0.965
1.025
1.035
1.043
1.019
1.040
1.004
1.014
1.026
1.065
1.073
0.995
1.037
1.068
1.036
1.058
1.088
C-3
-------
Appendix D - Total Water Management Literature Review
D.1 Literature Review Methodology
A literature review was conducted in order to better understand the potential for TWM. The review included planning
approaches consistent with TWM, as well as innovative water resources strategies that have been implemented in the
U.S. and internationally.
To make this review more useful, results from the literature search were summarized into four regions of the U.S.
West, South, Northeast, and Midwest (see Figure D-l). For each of these regions, climate and water resources drivers
were identified in order to characterize the regions and better align the water resources strategies that are summarized
here.
D.2 Water Resources Drivers
a-west
B
Figure D-1 Regions of the United States
Throughout the U.S., water resources issues are influenced by multiple regional drivers such as climate, population
trends, water quality, water supply and environmental issues.
D.2.1 West Region Drivers
Climate
Climate in theWestis th e m ost di verse of al 1 the regionsin theU.S. It ranges from arid to semi-arid in the
D-l
-------
southwestern portion, marine and Mediterranean along the coast, and highland in the mountain and northern portions
(Weathereye, 2009). Winters are typically cool to mild with average temperatures ranging from 30-40ฐF in the
mountain and Pacific Northwest areas, and 50-60ฐF in the southwest and along the coast (HowStuffWorks, 2009).
Summers are dry with low humidity, with average temperatures ranging from 50-70ฐF in the mountain and Pacific
Northwest areas, and 85-95ฐF in the southwest. The majority of precipitation falls along the coast or with increasing
elevation. Precipitation tends to occur with greater extent during the winter months in the form of rain in coastal
areas a nd s now in the m ountain and no rthern a reas. A verage a nnual rainfall ranges from 8 -15 i nches i n the
southwest, 16-64 inches along the coast, and as high as 96 inches in the Cascade Mountains. Snowfall can range from
32-64 inches in the mountains.
Population
Between 2000 and 2 005, popul ation g rowth i n t he W est outpaced a 11 o ther r egions, w ith a g rowth r ate of
approximately 8.1% (US Census B ureau, 200 5). G rowth r ates w ere the h ighest i n t he d esert s tates o f A rizona
(15.8%) and Nevada (20.8%), while lowest in the Rocky Mountain States of Montana (3.7%) and Wyoming (3.1%).
Water Quality Drivers
Within th e W est, water quality is dr iven by ach ieving com pliance with TM DLs, c ompliance with discharge
requirements, nonpoint source (NPS) pollution, total dissolved solids (TDS) management, and to a lesser extent CSO
concentrated in the northwest portion of the region. TMDLs have and continue to be adopted in sub-regions of the
West for both inland waters and oceans impacting both dry and wet weather discharges. Bacteria and metals are the
main TMDLs in the region. N PS pollution impacts both groundwater and surface waters in the West and requires
watershed-based management plans. Compliance with discharge requirements has required innovative solutions to
reduce discharge volumes and refinement in treatment processes. High TDS or salinity levels are prevalent in western
areas relying on water from the Colorado River and localized groundwater basins. High TDS levels adversely impact
groundwater and agriculture, as well as potentially limit the application of recycled water for urban irrigation.
Water Supply Drivers
Multiple factors drive availability of water supplies in the West including droughts, water rights issues, population
growth, environmental protection, and potential climate change. Outside of the pacific northwest, the West has few
large 1 akes or hi gh- flowing r ivers. S nowpack in t he r egion's m ountains accounts for the m ajority of w ater
replenishment for the region's rivers, man-made reservoirs, and groundwater basins. This fact makes the West highly
susceptible droughts and potential climate change. Further, most large river systems, such as the Colorado River, are
fully allocated; and competition between agricultural, urban and environmental demands for water is the greatest in
the West. Agriculture uses the vast majority of water in the West, upwards of 80%. Water right battles over Native
American rights and allocations of the Colorado River have been at the forefront of conflicts in this region.
High popul ation g rowth c oncentrated i n the de sert regions, w ith low annual p recipitation rates, further e xacerbate
water supply shortfalls. A nd finally, demands for the environment (e.g., minimum flows for fish) are increasingly
impacting water supply availability for urban and agricultural water use. In recent years, water deliveries from the
Klamath River in Oregon and the SWP in the Bay-Delta region of California have been significantly curtailed to
reduce environmental impacts to aquatic organisms (Oregon State University and University of California, 2001).
D.2.2 Midwest Region Drivers
Climate
Climate in the Midwest is characterized as humid continental in the eastern portion and semi-arid on the western edge
of the region (Weathereye, 2009 and HowStuffWorks, 2009). Winters are cold, with temperatures averaging 0-30ฐF
and snowfall ranging from 10-60 inches. Summers are warm, humid and wet, with average temperatures of 70-85ฐF.
Rainfall is generally heaviest in spring and summer months, averaging between 16-35 inches .
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Population
Population growth in the Midwest is low. Between 2000 and 2005 a growth of 2.4%, far lower than the national
growth rate of 5.3 % (US Census Bureau, 2005). Withinthe region, growth was highest in Missouri (3.6%)and
Minnesota (4.3%), while negative growth was experienced in North Dakota (-0.
Water Quality Drivers
Major water quality drivers in the Midwest i nclude CSO, sanitary sew er ov erflows (SSO), and NFS pollution.
Combined sewer systems (CSS) are prevalent throughout the Midwest and Northeast regions. Approximately 772
cities serving 40 million people in the U.S. are served by CSS (EPA, 2009a). At least 40,000 SSOs are estimated to
occur throughout the U.S. (EPA,2009b). S SOs a re caus ed by excessive runoff entering the systems, excessive
sewage flows, and/or mechanical failures in the system. NFS pollution attributed to urban and agricultural runoff is
increasingly becoming major water quality drivers in the region with impacts downstream and outside of the region in
the Gulf of Mexico. Contamination and water quality issues in the Great Lakes have been at the forefront of conflicts
in this region.
Water Supply Drivers
Water supply availability in the Midwest is generally a function of system delivery capacity, periodic droughts and
contamination o f fresh water s ources. Major mid-western urban centers are, for the most part, concentrated ne ar
rivers or lakes which are relatively drought resistant. These water bodies include the Great Lakes, Mississippi River,
and Ohio River. Droughts periodically occur throughout the Midwest and particularly impact agricultural areas and
suburban areas located away from major water bodies. However, settlement agreements between other states and
Canada have caused water shortages to occur in major urban areas, such as Chicago, Illinois.
Aging or lack of infrastructure to move water efficiently has caused the most water supply shortfalls in the regions,
mainly impacting suburban areas or cities that are not in close proximity to large water bodies.
D.2.3 Northeast Region Drivers
Climate
Similar to the Midwest, the Northeast climate is humid continental (Weathereye, 2009 and HowStuffWorks, 2009).
Winters are cold with temperatures averaging 0-25ฐF, and snowfall ranging from 32-100 inches. Summers are warm
and humid, with temperatures averaging 65-80ฐF. Noreasters in the winter provide steady, rain along the coast while
spring and summer thunder storms account for the remaining rainfall. Annual rainfall ranges from 32-64 inches.
Population
Population growth is the lowest in the Northeast region. The northeast region experienced the lowest growth rate of
all regions between 2000 and 2005 witha rate of approximately 2% (US Census Bureau, 2005), 3.3% below the
national average. Growth rates were highest in the northern states of Maine (3.7%) and New Hampshire (6.0%) and
lowest in Pennsylvania (1.2%) and Massachusetts (
Water Quality Drivers
Major water quality drivers in the Northeast include CSOs, TMDL requirements, pharmaceuticals and personal care
products (PPCPs) in water supplies, beach closures after major storm events related to high fecal coliform counts, and
presence of the parasite cryptosporidium in drinking water supplies. S imilar to the Midwest, CSOs are prevalent
throughout t he N ortheast with the m ajority of c ities following L ong T erm C ontrol P lans a nd m any c ities und er
consent decrees to reduce overflows. Control plan costs in major cities are in excess of a billion dollars. TMDL
compliance is leading to the development of new approaches throughout the East, with sediment the most common
TMDL. Flow based approaches, in areas where erosion is a major problem, are being developed. Contaminants from
PPCPs ar e a con cern for dri nking w ater supplier ing roundwater and surface water based systems. WWTPsare
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concerned about implications related to removal of the contaminants. After storm events beach closures along the
coast and inland rivers related to high fecal coliform counts are major concerns. Presence of cryptosporidium in
drinking water supplies is one of the most common causes of waterborne illnesses in the (U. S. Department of Health
and Human Services, 2009).
Water Supply Drivers
Water supply drivers in the Northeast are revolve around droughts and water allocation issues. Water supply issues
during normal climatic conditions are relatively minor, but recent droughts have driven drought related water supply
issues to the forefront. New Jersey suppliers and many smaller suppliers throughout the region have asked consumers
to conserve water during recent droughts with multiple areas declaring drought emergencies. Allocation of water
supplies impacts available water supplies for states and major metropolitan areas. Past battles over water supplies in
the Delaware River Basin led to the formation of the Delaware River Basin Commission in the 1961. Members of the
Delaware River Basin Commission, New York, New Jersey, Pennsylvania, and Delaware, work together to address
water management issues in the basin.
D.2.4 South Region Drivers
Climate
Climate in the South is characterized as humid and sub-tropical(Weathereye, 2009). Winters are mild in the south,
with little to no snowfall and average temperatures ranging 50-70ฐF (HowStuffWorks, 2009). Summers are hot and
humid, with temperatures ranging 80-90ฐF. Annual rainfall averages between 32-64 inches with significant rainfall
occurring both in the summer and winter.
Population
The S outh r egion e xperienced a hi gh g rowth r ate of a pproximately 7.3%, exceeding t he n ational av erage by 2 %
between 2000 and 2005 (US Census Bureau, 2005). Growth was highest in Georgia (10.8%) and Florida (11.3%) and
lowest in West Virginia (0.5%) and the District of Columbia (-3.8%).
Water Quality Drivers
Water qu ality i s d riven in the South byTMDLs, environmental resource pe rmits, and tourism. Major TMDL
impairments i n the S outh i nclude nu trients, ba cteria indicators, a nd d issolved oxy gen. Environmental r esource
permits are drivers of water quality in Florida. In Florida, environmental resource permits are required for projects
involving construction or a significant alteration to storm water or surface water management systems. Water related
tourism in the South is a major industry and providing clean surface and ocean water is essential to maintaining that
industry. C SOs are not prevalent in the South. I n a few sub-regional areas, including Atlanta and Columbus in
Georgia, Alabama, and Nashville, Tennessee CSOs are water quality drivers.
Water Supply Drivers
A multitude of factors drive water supply related issues in the South including droughts, an increasing population,
saltwater intrusion in aquifers in coastal areas, maintaining minimum flows and levels to ecological goals, and state
water negotiations, especially between Georgia, Alabama, and Florida. Droughts have been prevalent in the south
and are reinforced by the recent multi-year severe drought in Georgia. Population growth continues to place demands
on limited water resources in the South. Aquifer draw down in coastal areas is leading towards increasing levels of
saltwater intrusion into sources of drinking water. In areas such as Florida the majority of potable water supplies are
extracted from groundwater sources. Maintaining minimum flows and levels in surface waters at levels determined to
meet ecological goals for hydrology and water quality further reduces available potable water supply sources in the
South.
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Water supplies in the tri-state area of Georgia, Alabama, and Florida continue to be contested in federal courts in a
multi-decade battle over water supplies originating from Lake Lanier. Atlanta relies on Lake Lanier to supply its 3
million residents. Florida wants to maintain flows from the lake into Apalachicola B ay to maintain flows for its
oyster industry and federally protected fish and mussels. Alabama wants a portion of the Lake Lanier supplies to
operate its nuclear power plant near Dothan (Shelton, 2009).
D.3 Water Resources Strategies
Each region of t he U.S. has taken different a pproaches t o solving water resources pro blems ba sed on the
characteristics and drivers described above. Further, cost-effective solutions in one region may not be cost-effective
in another region due to these differences. Within this section TWM strategies are presented for each region of the
U.S. However, it should be noted that this does not represent the exhaustive list of what is occurring; but rather, this
is a representative sample of the types of TWM strategies that are being implemented across the country. The most
commonly i mplemented components o f TWM include w ater conservation programs, recycled water, stormwater
management, rainwater harvesting, graywater systems and integrated water management plans.
Regulatory constraints are also described to illustrate the myriad of regulations and variations that must be taken into
account when evaluating TWM. Finally, international TWM strategies are summarized to illustrate what types of
solutions are being implemented globally.
Before TWM strategies are implemented, they should be evaluated from an integrated perspective. For example,
implementing a graywater system not only provides a new water supply for summer irrigation, but will also reduce
flows to wastewater system facilities. On the other hand, a substantial effort of rainfall harvesting to increase water
supply by recharging groundwater may have localized undesirable impacts to groundwater table due to mounding, if
the soils are not characteristically prone to infiltration. Therefore, it is important to take a "systems" approach that
examines all impacts: water supply, wastewater, stormwater, and the environment when evaluating TWM. Chapter 3
of this report presented an approach for how TWM should be evaluated in order to make sure t hat a 11 costs and
benefits are incorporated into the decision making.
Knowledge sharing among leading experts and development of solutions applicable to water resources management
issues occurs throughout the world at conferences and workshops. Many sources cited in this literature review are
from abstracts presented at these conferences. In 2006, leading environmental specialists, scientists, and engineers
from e ight c ountries, including m embers of the N ational A cademy of E ngineering and endowed chair pr ofessors,
gathered to participate in the Wingspread International Workshop Cities of the Future - Bringing Blue Waters to
Green Cities. Much of what w as p resented at this f irst-of-the-kind w orkshop i s d irectly a pplicable to TWM.
Proceedings of t he w orkshop w ere pub lished i n Cities of the F uture. Towards Integrated Sustainable Water an d
Landscape Management (Novotny and Brown, 2007).
D.3.1 West Region Strategies
In the West many agencies have prepared integrated water resource plans and have initiated efforts to identify non-
traditional water supplies and conservation efforts. Water supply reliability is at the forefront of planning efforts in
the West to address periodic prolonged drought periods and growing populations in an arid region. Efforts in the
West are focused on developing non-traditional water supplies to supplement traditional supplies and complying with
TMDLsin a cost-effective m anner. In the West, wet-weather runoff e ducation focuses on c apturing runoff to
conserve w ater and recharge g roundwater. While most areas have no t formally a dopted TWM, they have made
significant strides in utilizing integrated water resources planning to examine the whole water cycle as a part of long-
range water supply planning.
Integrated Resources Planning
IRP is a technique that explores both supply-side and demand-side strategies to meet multiple objectives. IRP
estimates the total lifecycle costs (capital and O&M costs over the entire planning horizon) and fully examines risk
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and uncertainty. A nd unlike traditional planning, IRP involves stakeholders in the decision-making process. The
American Waterworks Association (AWWA) has formally incorporated IRP in its updated M50 manual on water
resources planning (AWWA, 2007).
Although IRP has mainly been applied solely to water supply planning, the technique can also be applied across all
water resources (drinking water, wastewater, and stormwater). When IRP is applied in this manner, it comes very
close to TWM. However, there are only limited case examples where IRP has been applied in this manner.
In 1999, Los Angeles embarked on the development of an IRP utilizing a unique approach of technical integration
and community involvement to guide water resources and facility planning at the watershed level for 20 years. The
City was faced with many challenges, including dr oughts, wastewater c apacity i ssues, compliance with TMDLs,
aging infrastructure, quality of life issues, environmental regulations, and community concerns with facility siting and
expansions. The IRP took a bold new approach and represented the first time that various city departments worked
together to solve comprehensive water resources issues. From our literature search, this IRP represents the closest
application of TWM that exists today. For this reason, it was selected as the TWM Case Study for this study (see
Chapter 4 of the main report).
Another similar concept to TWM is integrated watershed planning. In California, all watershed regions must develop
comprehensive Integrated Regional W ater M anagement P lans (IRWMPs) to be eligible for state funding of w ater
resources p rejects. I RWMPs m ust add ress w ater supp ly, water qu ality, stormwater, flood management,
environmental r estoration a nd r ecreation. This process al so involves multi-agency go vernance a nd r egional
cooperation not seen in any other part of the country. In many ways these IRWMPs represent a watershed version of
TWM.
Other integrated resources plans that have been implemented in the West include:
Butte County, CA
Eastern Municipal Water District, CA
Metropolitan Water District of Southern California, CA
Rancho California Water District, CA
San Diego, CA
Santa Clara Valley Water District, CA
Santa Ana Watershed Protection Authority, CA
Colorado Springs, CO
Denver, CO
Santa Fe, NM
Portland, OR
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Indirect Potable Water Reuse Projects
Planned indirect potable water reuse is the reuse of highly treated wastewater in an indirect manner, such as allowing
percolation i nto ana quifer us ed f or g roundwater pr eduction. P lanned i ndirect pot able r euse of r eclaimed w ater
occurs in multiple locations t hroughout the West and country. A f ew o f the m aj or facilities in the West are
highlighted here. The proposed State of California treatment and testing criteria for groundwater recharge were
published i n a W orld H ealth O rganization W ater ( 2003) r eport on t he po tential r isk of us ing w astewater f or
groundwater recharge.
Orange County Water District and Orange County Sanitation District
Fountain Valley, CA
Groundwater Replenishment System:
Seawater i ntrusion barrier, indirect pot able w ater r euse t reated with advanced treatment con sisting of
microfiltration, reverse osmosis, ultraviolet light, and hydrogen peroxide
Production: 72,000 Acre Feet per Year (Phase 1)
Spreading of treated wastewater for percolation into deep groundwater aquifers
Replaced Waterworks F actory 21 completed in 197 6 for recycled w ater barrier i njection (Orange C ounty
Water District, 2009)
Water Replenishment District of Southern California, Montebello, CA
Montebello Forebay Natural Groundwater Recharge Project:
Spreading of treated wastewater to augment existing groundwater supplies for use as drinking water (35% of
total recharge to groundwater basin is treated wastewater)
In operation since 1962
West Basin Municipal Water District, Carson, CA
Membrane Treatment Facility:
Injection (pumping water into aquifer instead of withdrawing water) of treated wastewater into aquifers for
groundwater barrier also produces "designer" recycled water treated for specific industrial and irrigation uses.
Production: 33,600 AFY
Online 1995
Water Replenishment District of Southern California, Long Beach, CA
Alamitos Barrier Reclaimed Water Project:
Injection of a blend of treated wastewater and potable water to form a groundwater barrier
Production: 30 AFY
Phase 1 completed 2005
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Aurora Water, Aurora, CO
Prairie Waters Project:
Wells alongside the banks of t he Lower South Platte River, below Denver Metro Reclamation Facility
(WWTP); takes advantage of river bank filtration and incorporates aquifer storage/recovery before pumping
to a water filtration plant and blending with reservoir water
Production: 10,000 AFY (2010) (Aurora Water, 2009)
Scottsdale Water Resources Department, Scottsdale, AZ
City of Scottsdale Water Campus:
Injection of treated w astewater into aquifer for withdrawal as drinking water supplies, also used for golf
course irrigation
Production: 24,640 A FY ( 13,440 A FY golf c ourse, 11,20 0 A FY advanced t reatment for g roundwater
replenishment) to be expanded to 26,880 AFY for irrigation, 24,640 AFY for advanced treatment
In operation since 1998
Cloudcroft, NM
Cloudcroft Indirect Potable Water Reuse:
Blending with other well and spring water, as part of drinking water supplies
Production: 112 AFY
Designer Recycled Water
The West Basin Municipal Water District ap rovider of po table and recycled water located in Carson, California
produces de signer recycled w ater. R ecycled w ater is pr oduced at their West B asin Water Recycling F acility t o
varying water quality levels to meet specific end user requirements. The recycling facility receives secondary effluent
from Los Angeles' HTP and provides additional levels of treatment based on the ultimate use of the recycled water.
Production to a prescribed water quality level allows recycled water to be produced at the greatest cost-effective level
necessary. Five types of recycled water are produced by the recycling facility:
Disinfected T ertiary Water - Secondary treated water from HTP treated to Title 22 standards u sed for
industrial and irrigation purposes
Nitrified Water - Tertiary treated water with ammonia removed by nitrification used in industrial cooling
towers
Softened Reverse Osmosis Water - Secondary treated water from HTP pretreated with microfiltration and
lime softeners and then reverse osmosis, for use in the seawater barrier
Pure R everse O smosis Water - Secondary t reated w ater from H TP pr etreated w ith m icrofiltration and
additional treatment w ith reverse osmosis for use in low pressure boiler feeds, for use industrial sites and
refineries
Ultra Pure Reverse Osmosis Water - Secondary treated water from HTP pretreated with microfiltration and
then treated twice with reverse osmosis to ensure minerals are removed, for use in high pressure boilers
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Recycled water from WBMWD is used for groundwater replenishment, landscape irrigation, and industrial processes.
Decentralized Recycled Water Systems
Decentralized recycled water systems or "satellite treatment facilities or scalping plants" have become popular as
many ar eas ex perience s evere w ater supp ly shortages. S atellite treatment facilities ar e w astewater reclamation
facilities constructed at or near the point of use, and sized for a reclaimed water demand as opposed to a w astewater
treatment need. These facilities are often constructed in close proximity to urban areas.
At a minimum satellite treatment facilities must address the following questions:
Is there enough wastewater flow in the area to meet the reclaimed water demand?
Is there land available for construction of a satellite plant?
Will the public accept a water reclamation facility in their neighborhood?
Expected cost of the facility vs. other reclaimed water options?
The benefits of using satellite treatment facilities in urban areas include:
Compact footprint
Minimal operator attention
Easily enclosed and architecturally treated to meet surrounded architecture
Sustainable water resource management (Rimer, et al, 2003).
In Wash ington State, the LOTT al liance, the r egional w astewater t reatment sy stem ser vicing t he c ities o f L acey,
Olympia, T umwater, a nd nor them Thurston C ounty, ha s de veloped a long r ange w astewater m anagement pi an
focused on constructing three satellite treatment facilities. Two of the facilities are constructed with reclaimed water
used for recharge, i rrigation, dust suppression, boat w ashing, c onstructed w etlands, and other us es. The facilities
were designed to treat 1 MOD with incremental expansion to 5 MOD in a just-in-time construction process to meet
future capacities when needed (LOTT, 2009 and McCauley and Dennis-Perez, 2008).
Urban Runoff Reuse
Santa Monica's Urban Runoff Recycling Facility (SMURRF) captures dry weather runoff for treatment and reuse and
treats up to 0.5 MGD from the City's two main storm drains. Treated water is used for landscape irrigation and toilet
flushing at public facilities to offset potable water demands. The facility will potentially offset 4% of the City's daily
water use. Additionally, the facility was designed for the public to walk through to access the beach to serve as an
educational source. The facility and recycled water distribution system cost approximately $12 million (City of Santa
Monica, 2009).
Rainwater Harvesting
Rain barrels and cisterns are low co st o ptions for collecting rainwater from impervious surfaces reducing pe ak
stormwater flows and conserving water. Cities throughoutthe West (where it is legal to harvest rainwater) have
encouraged rainwater harvesting to reduce runoff an d conserve water. Some states, such as Hawaii have be en
practicing rainwater harvesting for years due to limited water resources.
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In cities such as Seattle and Portland where downspouts are typically directly connected to C SS, rain barrels and
cisterns have the added benefit of reducing combined sewer overflows during storm events. Rain barrels are typically
installed aboveground at buildings to collect water from impervious roof surfaces for future outdoor water use.
Cisterns can collect water from multiple types of impervious surfaces including roofs, play grounds, and artificial turf
sports fields. Stored water serves as a source of chemically untreated soft water for outdoor irrigation needs. Water
savings f rom r ain barrels a nd c isterns a re de pendent upon the storage v olume a nd t he num ber i nstalled i n a
jurisdiction.
Many jurisdictions a re e ncouraging t he installation of r ain b arrels a nd cisterns t hrough c ustomer e ducation and
handouts on installation techniques. Multiple cities, such as Seattle offer programs where residents can purchase rain
barrels at a subsidized cost savings of $15 compared to other vendors. Water savings from rain barrels and cisterns
are dependent upon the storage volume and the number installed in a jurisdiction. In Portland, rainwater can also be
used for toilet flushing with a permit. Table D-l provides estimated material and installation costs for rain barrels and
pre-fabricated cisterns.
Table D-1
Estimated Rain Barrel and Cistern Costs
Type
Single Rain Barrel
Polyethylene Cistern
Polyethylene Cistern
Fiberglass Cistern
Fiberglass Cistern
Size (gallons)
60
165
1,800
5,000
10,000
Materials
$120
$160
$1,100
$5,000
$10,000
Installation
$96
$400
$1,000
$1,500
$2000
Total
$216
$560
$2,100
$6,500
$12,000
Source: CH:CDM, City of Los Angeles Integrated Resources Plan, Facilities Plan, Volume
3: Runoff Management, 2004
Green Roofs
Portland, Oregon has taken measures to incentivize the installation of green roofs or eco-roofs which are roofs that
can help manage stormwater along with providing other environmental benefits. These programs include:
Bonus floor to area ratios for new buildings in the central core based on eco-roof coverage in relationship to
the bu ildings footprint - 10-30%, 30 -60%, a nd 60 % or g reater results i n b onus o f one , two, a nd t hree
additional square feet per square foot of green roof, respectively.
Use of eco-roofs in Central to satisfy Design Guidelines requirement of integrating roofs and use of rooftops
Requirement that all new projects have an eco-roof and/or Energy Star rated roof material
Potential funding through City of Portland Green Investment Fund
Requirement of eco-roofs is developer agreements in specified areas (City of Portland, 2009).
Lawn Buy-Back Rebate Programs
Throughout the W est, 1 awn buy -back prog rams or r ebates are i ncreasingly g aining pop ularity i n various forms.
Typical p rograms i nvolve t he r emoval of t urf and replacement w ith a xe riscape or na tive p lants i n a m anner that
remains aesthetically appealing. Hybrid programs involve the replacement of turf with artificial turf.
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Southern Nevada Water Authority
Southern Nevada Water Authority has been offering rebates since 1999 and has conducted an extensive study funded
by t he B ureau of R eclamation on the c onversion oft urf to x eric 1 andscaping or w ater e fficient landscaping.
Completed in 2005 the study indicates turf replacement is an effective means of reducing water consumption within
its member agency jurisdictions. Since inception of the program in 1999 to the end of 2007 over 100 million sq ft of
turf area has been converted to water efficient landscaping. This program coupled with other conservation programs
has reduced water demands by 14% between 2002 and 2006 while the population increased by 400,000.
The Authority's study indicates conversion of one square foot of turf to a xeriscape saves on average 55.8 gallons of
water per year or an equivalent to 89.6 inches of rain as illustrated in Table D-2. Total residential water consumption
decreased by approximately 30% for turf conversion participants. Turf requires approximately 73 gallons ofwater
per square foot annually or an equivalent of 117.2 inches of rain while a typical xeriscape requires 17.2 gallons of
water or 27.6 i nches of rain for an equivalent area in the study area. W ater use tends to drop immediately upon
conversion with no decay in savings overtime.
Examples of rebate programs offered by other agencies are shown in Table D-3.
Table D-2
Lawn Buy-Back Water Savings and Costs1
Water Efficient Landscape
Converted from Turf
Average Savings per Square Foot
per Year
Gallons
55.8
Rainfall Equivalent
(Inches)
89.6
Average Installation Cost per square
foot ($)
Self
1.37
Contractor
1.93
Average
1.55
1. "Xeriscape Conversion Study Final Report" by K. A. Sovocool, Southern Nevada Water Authority, 2005.
Smart Irrigation
Smart i rrigation or E T c ontrollers c ontrol the a pplication o f w ater from out door i rrigation s ystems ba sed on local
weather conditions. These controllers reduce water use by adjusting watering times on a daily basis to reflect actual
weather data, including ET, soil moisture, precipitation, and other factors. Water savings rate vary by user types and
geographic locations. S mart i rrigation c ontrollers a Iso h ave t he a dded be nefit of r educing dr y w eather r unoff
associated with overwatering. Municipal W ater District of O range C ounty (MWDOC) a nd Irvine Ranch Water
District (IRWD) in California completed pilot study regarding controller efficiency (MWDOC and IRWD, 2004).
Results are summarized here.
Water savings attributed to smart irrigation systems vary based on the land use (residential or large landscape users),
local landscaping, and geographic location. These studies have indicated that water savings experienced in the first
year i s m aintained in subsequent y ears an d a decay i n the w ater s avings i s not experienced in t he y ears after
installation of the controllers.
Table D-4 presents savings associated with installation of smart irrigation controllers for single-family residential and
large landscape users based on joint IRWD, MWDOC and US Bureau of Reclamation studies. Savings are provided
in terms of gallons per day (gpd), gallons per year (gpy), and percent of total water saved. For large landscape users
percent saved is a more applicable measure of savings as large landscaped areas can vary dramatically in size.
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Table D-3
Example Lawn Buy-Back Rebates for Other Agencies
Agency
Santa Clara Valley Water District, CA
Residential
Non-Residential
North Marin Water District, CA
Residential
Metropolitan Water District of Southern
California
Non-Residential
Aurora, CO
Residential
Non-Residential (includes multi-family
and HOAs)
Glendale, AZ
Residential Existing
Residential New
Non-Residential (includes multi-family
and HOAs)
Scottsdale, AZ
Residential
Non-Residential (includes multi-family
and HOAs)
Rebate
Santa Clara County: Up to $1 ,000; Morgan
Hill and Palo Alto $150 per 100 sq. ft. with
residential maximum of $2,0001
Santa Clara County: Up to $10,000; Morgan
Hill and Palo Alto up to $20,0001
$50 per 100 sq. ft with maximum of $400 for
single-family, $100 for town houses, condos,
and apartments; Additional rebate up to $100
for mulch for 25% of mulch cost
$0.30 per sq ft/$1 3,000 per acre
$1 per sq. ft converted
$1 per sq. ft converted
Up to $750, varies by tiers of turf removal
$200
$1 ,500 for completion of Water Budgeting
Program and $150 per 1,000 sq. ft. of grass
removed
Option 1 : $0.25 for turf removal only;
Option 2: $0.50 for turf removal and low wate
plant installation ; Maximum of $1 ,500
25% of total costs, excluding taxes;
Maximum of $3,000
Summary
Replacement of high water use plants with plants on
agency approved list or permeable hardscape; No
artificial turf, Must remain for 5 years, No net increase in
irrigated area, No pop-up sprinkler irrigation; Requires pre
inspection
Replace with California native low water use plants;
Mulch to at least 4 inches; Requires lawn irrigation to be
replaced
Synthetic turf must replace irrigated areas; Available for
new or retrofit landscapes; No minimum or maximum
areas; Member agency must be a participant in rebate
program
Minimum area of 500 sq. ft, maximum of 10,000 sq. ft.;
50% of new xeriscape must be covered with plants; Must
submit design drawings to scale (City offers design
classes); Any unhealthy or dead plants in 2009 must be
replaced; Specific plants sizes are required; Seeding doe:
not qualify for rebate; 2-3" of mulch required; Requires
pre-approval and post-inspection
Minimum area of 500 sq. ft, maximum of 10,000 sq. ft.;
Same requirements as above
Minimum of 500 sq. ft of turf removed; Removal area
must be landscaped; 75% of plants must be on State's
low water list;
More than 50% of total landscape must be non-grass not
including driveways, pools, patios, and walkways;
Landscape area must exceed 1 ,000 sq. ft.; Both front and
back must be landscaped - no bare soil; More than 75%
of plants must be on State recommended low water use
list
Maximum of $3,000 per application per year; Must
participate in Water Budget Program; Minimum of 1 ,000
sq. ft. of grass removed; No bare soil; Must submit 3
estimates of work
No impermeable weed barriers; Exposed soil must be
covered, if granite used must be 2 inches thick; Pre and
post inspections required; Option 2 requires 50% plant
coverage of converted area with plants listed on State low
water plant list;
Minimum of 1 ,000 sq. ft. of lawn area to be converted to
low water use landscaping; Approved landscape plan
required from Planning and Development Services; Pre
and post inspections required; Contractor bid and
itemized receipts to be submitted
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Table D-4
Smart Irrigation Controller Water Savings and Costs
Single-family Residential
Large Landscape Users
Average Savings per User1'2
Day (GPD)
41
545 - 601
Year (GPY)
14,965
198,925-219,365
Percent of Total
Water Saved (%)
8
16
Cost per Unit
($)3
315-2,399
N/A
1 . "The Residential Runoff Reduction Study" Municipal Water District of Orange County and Irvine
Ranch Water District, July 2004.
2. "Commercial ET-Based Irrigation Controller Water Savings Study" Prepared for Irvine Ranch Water District
District and US Bureau of Reclamation by A & N Technical Services, September 2006.
3. Not including installation.
Referenced studies indicate single-family residential water savings associated with installation of a smart irrigation
controller a re approximately 41 gpd per residence or approximately 14,965 gpy per residence. This resultsin a
savings of approximately 8% of total water use for a typical household in the study area, which is approximately an
18% reduction in estimated landscape water use. The bulk of r esidential savings occurs in the fall and summer
months.
Large landscape user savings varies between 545 to 601 gpd per user or approximately 198,925 to 219,365 gpy.
Large 1 andscape us ers i nclude u sers w ith dedicated landscape m eters i ncluding pa rks, medians, homeowners
associations, multi-family residential 1 andscape a reas, and commercial/industrial businesses. As indicated by the
studies, these users typically experience a 16% savings in water use with installation of smart irrigation controllers.
Water reductions associated with large landscaper users are typically eight times greater than single-family residential
users.
Controllers are designed as retrofits to replace existing automatic irrigation controllers orto be designed as new
controllers for new landscaping. C osts vary dependent upon the designed use. A s illustrated in Table 3 -3, typical
single-family residential c ontrollers range i n p rice from $315 t o $2,399 de pendent upon the s elected systems and
options. Costs for controllers for large landscapes vary dramatically based upon irrigation system requirements and
are largely a function of the number of irrigation valves. The greater the number of valves the greater the number of
controllers required to operate the system. Installation varies based on the selected installer and is not included in the
controller pr ice range. The IRWD studies (IRWD and U S Bureau of R eclamation, 2006) indicate professional
installation is recommended to correctly set-up the controller for local weather conditions, including precipitation.
Controllers receive data from local ET stations via various methodologies, including the internet, satellites, and local
stations installed at the point of application as a part of the controller. Monthly subscription fees are required for
internet and satellite updates. Most manufacturers provide the service for free for the first year. Stations installed as
part of the controller do not require subscription fees.
Many water agencies offer rebates to customers installing smart irrigation controllers. I n the IRWD service area
rebates for single-family r esidential customers are currently $60 per activated valve. For large landscape users
rebates are $750 per irrigated acres. Rebates are a sum of IRWD and the local wholesaler, MWDOC. Dependent
upon installation charges and the selected controller the rebates may potentially offset the entire cost of the controller
and installation (MWDOC and IRWD, 2004 and IRWD and US Bureau of Reclamation, 2006).
Residential Indoor Dual Plumbing Systems
Indoor dual plumbing i s an additional set of plumbing waterlines to deliver reclaimed water for n on-consumptive
uses, such as toilet and urinal flushing and cooling towers in high rise buildings. In the United States dual plumbing
for toilet and urinal flushing includes commercial buildings, public facilities, universities, jails, and more recently
residential high rises.
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Irvine Ranch Water District, California
IRWD received the first unrestricted recycled water use permit in California in 1991 allowing for the installation of
dual plumbing systems in its service area. IRWD determined that 70-90% of water use in commercial buildings was
used for toilet and urinal flushing. A study was conducted indicating that the use of reclaimed water was feasible in
buildings over six stories for flushing toilets and urinals and priming floor drain traps. IRWD initially subsidized the
incremental cost of dual plumbing systems for two high rises. Dual plumbing raised the overall plumbing costs for
the building by approximately 9%. A fter three years, water charges for one of the bu ildings w ere approximately
$6,200. Without dual plumbing costs were projected at approximately $22,800 resulting in a savings of over $22,000.
Since that time 15 buildings are using recycled water for toilet flushing. IRWD requires all non-residential buildings
over 80,000 sq ft to be dual plumbed (Crook, 1998).
Indoor Water Conservation
Many large water utilities in the We st have incentive programs or prov ide rebates for replacing high water using
fixtures with high efficiency models, such as toilets, urinals, clothes washing machines and dishwashers. Examples of
large regional rebate programs for indoor water conservation include:
Metropolitan Water District of Southern California
San Diego County Water Authority
Denver Metropolitan Area
Seattle Metropolitan Area
Phoenix Metropolitan Area
In Los Angeles, for example, over 1 million ultra low flush toilets were provided since 1991 as a result of these types
of rebate programs.
D.3.2 Midwest Region Strategies
In the Midwest, agencies are addressing portions of TWM that tend to impact the region. Efforts in the Midwest are
focused on addressing water quality issues of CSOs, SSOs, NFS pollution and to a lesser extent water supply issues
such as conservation, peak demand reductions, and water reuse. In the Midwest stormwater management solutions do
not tend to focus on conserving water or increasing recharge as a means to increase water supplies, but rather focus on
reducing peak runoff during storm events as a means to reduce CSOs, SSOs, and NFS pollution. A large portion of
the population centers in the Midwest are centered on the Great Lakes region. With such a vast water supply in the
past water was not conserved. Efforts in areas, such as Chicago, are beginning to address water conservation at the
government level and at t argeting out reach to residents. Methodologies summarized here are innovative at the
regional or national level and can be applied elsewhere as a part of a TWM strategy.
Milwaukee, Wisconsin
Milwaukee, Wisconsin has undertaken multiple initiatives to address water quality and water conservation issues.
The City's Office of Environmental Sustainability has developed a green program for the City with facets including
water quality improvement. Milwaukee Metropolitan Sewerage District has initiated a $ 1 billion overflow reduction
plan to be completed by 2010 to reduce CSO and SSO to receiving waters. Additional benefits of the plan include a
reduction in NFS pollutants. Applicable sections to TWM include stormwater reduction and flood management, each
with applications to water conservation. P rior to initiating efforts to reduce CSO/SSO an average of 8 to 9 billion
gallons of water in the sewer system was released to Lake Michigan per year. Programs with application to TWM are
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summarized here. All sewer overflows in this section refer to both CSO and SSO (Milwaukee Metropolitan Sewerage
District, 2009 a,b).
Greenseams Program
More than 1,600 acres of undeveloped private property exhibiting soil properties acceptable to infiltration to reduce
flooding ha ve b een purchased through the The C onservation F und (Milwaukee Metropolitan S ewerage D istrict,
2009c), a national non-profit organization that handles program operations. This voluntary program targets properties
in areas forecast to have major growth in the next 20 years and areas along streams, wetlands, and shoreline of Lake
Michigan. L and acquisitions will be restored and maintained to store rain and snow. A ncillary benefits include
wildlife habitat preservation and recreation opportunities.
Rain Gardens
To reduce polluted runoff and sewer overflows, rain gardens are encouraged through a grant program. G rants are
awarded via approximately 50% reductions in the price of plants suitable for a rain garden. Grants do not include the
planning, design, and construction of the rain garden. G rant recipients must provide transport the plants from the
pick-up location. Eligible applicants include government, residents, and groups. Schools receiving grants must post a
sign paid for by Milwaukee Metropolitan Sewerage District next to the garden (Milwaukee Metropolitan Sewerage
District, 2009d).
Rain Barrels
Rain barrels are provided to residents throughout Wisconsin at a cost of $30 per hook-up ready, 55 gallon barrel. The
program is designed to reduce water use, save energy, reduce sewer overflows and polluted runoff, and protect Lake
Michigan (Milwaukee Metropolitan Sewerage District, 2009e).
Conservation Best Management Practices
The district provides customers with a list of BMPs designed to reduce water consumption, sewer overflows, polluted
runoff, and energy costs. Water conservation BMPs include:
Postpone laundry to periods when heavy rain is not forecast
Reduce shower times
Turn off water while shaving and brushing teeth
Fix leaky plumbing
Install high efficiency plumbing (Milwaukee Metropolitan Sewerage District, 2009f).
Stormwater Pilot Programs
Multiple pilot programs were initiated as part of the Stormwater Runoff Reduction Program. These programs are
discussed and evaluated in detail in The Application of Stormwater Runoff Reduction Best Management Practices in
Metropolitan Milwaukee in 2007. Pilot programs evaluated included low impact development projects including rain
gardens, green roofs, pervious pavement, low, downspout disconnection, wetlands, and cisterns. A review of BMPs
to determine negative impacts on sewer infiltration an inflow was also conducted. Innovative programs are discussed
in more detail elsewhere in this section (Milwaukee Metropolitan Sewerage District, 2007).
Menomee Valley Stormwater Park
Menomee Valley Stormwater Park was created to improve Stormwater runoff water quality from a 100-acre business
park. Park water quality components in elude three detention cells mimicking a treatment train with a wet prairie,
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wetland forest, and an emergent w etland. A dditional be nefits include pi ay fields, natural areas, and river access
(Milwaukee Metropolitan Sewerage District, 2007).
Menomee Valley Bioretention facility
The Menomee Valley Bioretention Facility, a two-acre shallow water area with vegetation was created to filter runoff
stormwater runoff from approximately 70 acres. Highlights of the facility include the use of permeable soils with a
clay liner and underdrain to discharge treated water to the Menomee River. Grasses and forbs (e.g., sunflower, clover
and milkweed) were planted to maximize ET and reduce peak runoff flows and volumes entering the river.
Additional benefits include habit and aesthetic improvements in an urban area (Milwaukee Metropolitan Sewerage
District, 2007).
Menomee Central Valley Planning
In a joint effort between Milwaukee Metropolitan Sewerage District, City of Milwaukee, Menomee Valley Partners,
Milwaukee T ransportation P artners, Sixteenth Street C ommunity H ealth Center, and private 1 andowners, an
integrated approach to stormwater management in the Menomee Central Valley was developed. An outcome of the
process was the development of c oordinated projects to serve the area, such as redevelopment of the stockyards to
include a regional treatment system and the previously discussed Menomee Valley Biorention Facility.
A Cooperative Agreement was signed between the stockyard redeveloper, Menomee Valley Partners, and the City to
create a comprehensive stormwater plan for the parcel with a regional treatment system. The City will construct and
fund the system up t o $1 million along with providing technical and financial support. P hase 1 o f the project will
treat runoff from a fi ve-acre right o f w ay and 10 acres of de velopment on the st ockyards si te us ing a t wo-acre
treatment system. Phase 2 will expand the system to four-acres to treat an additional 20- acres of private property. A
goal of the system is to assist property owners in complying with state and local stormwater regulations.
As part of the agreement the City is taking an innovative approach to ensure the system is regionally used by other
property owners. One approach is to amend the City's stormwater ordinance to require future development to use the
system. Another approach is to create a renewal plan, stormwater, or zoning overlay district requiring offsite property
owners to pr ovide cost s haring f or c onstruction, op eration, and maintenance oft he regional sy stem (Milwaukee
Metropolitan Sewerage District, 2007).
Pharmaceutical Collections
Milwaukee Waterworks was one of the first cities in the country to test source waters for PPCPs. An outgrowth of
testing for PPCPs was the establishment of medicine collection days to reduce the introduction of PPCPs in treated
wastewater to its source waters of Lake Michigan (Milwaukee Waterworks, 2009).
Minneapolis, Minnesota
Originally utilizing a CSS to handle wastewater and stormwater, the City of M inneapolis has separated more than
95% of the system to reduce CSOs and improve water quality. Separation of the outstanding portions of the system
are difficult and expensive, thus the City embarked ona five-yearplan to reduce future CSOs. Effortsto reduce
runoff ha ve i ncluded g reen r oofs, r ain g ardens, pe rvious pa vement i nstallation, r ain ba rrels, t ree pi anting, a nd
mandatory downspout disconnection from the sanitary sewer system (Minneapolis, 2009a and b).
University of Minnesota Subsurface Stormwater System
When c onstructing t he ne w T CF B ank S tadium a 11 he U niversity of M innesota i n M inneapolis, a s ubsurface
stormwater sy stem t o reduce stormwater runoff and improve water quality prior to discharging to the Mi ssissippi
River, was included within the project. An Environmental Passive Integrated Chamber system was installed beneath
an open space area that is also used for broadcast trucks, emergency vehicles, and other vehicles to maximize space
and eliminate above ground detention areas. The grass landscaped area can support the weight of vehicles with the
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use of geomembranes while retaining 60,000 gallons of water be low the surface. The system is expected to remove
70-85% of TSS and up 35% of pathogens (Geosynthetics, 2009).
Illinois Statewide Planning
To address future water demands, Illinois initiated a statewide water planning program in 2006 based on anticipation
of needing 20-50% more water in future decades to meets economic and residential needs. A goal of the program is
to encourage regional planning beyond local and county boundaries and to examine entire water cycle. Two regions
have started efforts to develop regional planning, Northeast Illinois and East-Central Illinois. At this stage the regions
have not de veloped water management opt ions, but a re c urrently c onsidering a pi ethora o f w ater s upply opt ions
(Illinois Water Supply Planning, 2009).
Within Illinois, the City of Chicago is at the forefront in addressing water related issues. Examples of the programs
implemented to address water issues with applicability to TWM are presented below.
Chicago, Illinois
In 2003, the Mayor of Chicago, Richard Daley, issued Chicago's Water Agenda 2003 focusing on three interrelated
main points regarding water: water conservation, water quality protection, and stormwater management. The agenda
recognizes problems associated with these three interrelated aspects of water and establishes actions the City can take
to address issues. Actions include changes the City can make in its operations and potential changes to building
codes. The document concludes w ith development of outreach and mobilization actions to develop long terms
solutions and educate citizens. This high level document establishes actions to guide the City as it moves forward in
proactively addressing the components of the water cycle (City of Chicago, 2003).
A few examples of actions taken to date on behalf of the City include:
Installation of shut-off buttons on drinking fountains
Street medians designed to capture storm runoff and remove pollutants
Diversion of runoff in new construction away from sewers
Installation of 1 million sq ft of green roofs on a combination of public and private buildings
Repairing leaking water mains attributing to an estimated 19% reduction in water consumption.
Stormwater C onservation. The C ity of C hicago ha s i mplemented a s tormwater c onservation pr ogram tor educe
CSOs and im prove in filtration o f s tormwater. An additional be nefit of t he p rogram i s w ater cons ervation. This
program includes encouragement of the following stormwater conservation m easures in conjunction with public
education:
Green design in public and private buildings including green roofs
Biofiltration with rain gardens to promote onsite infiltrations
Naturalized detention basins to detain stormwater onsite
Drainage swales to retain stormwater
Filter strips to slow the speed of runoff from impervious surfaces
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Natural landscaping to reduce water consumption and stormwater runoff
Permeable paving to promote infiltration of rain and snow melt
Downspout disconnection
Installation of rain barrels and cisterns (City of Chicago, 2009a).
Meter Save. MeterSave, a volunteer program implemented by the City of Chicago Department of Water Management,
is designed to allow residences to switch from non-metered billing to metered billing. The program provides a seven
year guarantee that the water bill with a meter will be no higher than the non-metered rate. As an additional incentive
to switch to a meter the choice of a rain barrel, outdoor water conservation kit, indoor water conservation, or water
meter monitor is provided to customers. The goal of the program is to reduce water consumption and protect Lake
Michigan (City of Chicago, 200b).
Residential Graywater System. Chicago's first residential graywater system in a residential building opened in 2007
in theNear North Apartments, a privately operated facility de signed for 1 ow-income anddisabled residents. Gray
water is collected from showers and bathroom sinks and treated onsite. Recycled water is then used for toilet
flushing. The project is expected to conserve approximately 45,000 gallons of water a year (Sokol, 2007).
Intake Restrictors on Catch Basins. Almost 2 00,000 inlet restrictor valves were installed throughout Chicago in
catch basins to reduce peak flows during storm events to the CSS. Restrictors slow peak flows into the system using
the streets as t emporary s torage areas (Walesh, 199 9). Reductions i n pe ak flows reduce w ater q uality i ssues
associated with CSO d ischarges t o waterways and r educe t he pos sibility of ba ckflows from t he sy stem i nto
basements. The overall cost was approximately $75 million, a quarter of the cost of comparable sewer improvements
with the same benefits (City of Chicago, 2009c).
Indianapolis, Indiana
Indianapolis, Indiana's two major water issues revolve ar ound water quality in waterways and occasional peak
demands exc eeding w ater sy stem capa city. Indianapolis i s a un der a cons ent decree from t he EPA and I ndiana
Department of Environmental Management to reduce raw sewage overflows into waterways. Efforts to comply with
the decree and to reduce peak water demands are highlighted in this section.
Sewage Overflow Long Range Control Plan
To improve water quality and comply with the consent decree the City if Indianapolis has implemented a long-term
program aimed at reducing the occurrences of sewage overflows into waterways. Currently, the White River and its
tributaries do not meet Indiana state standards for dissolved oxygen to protect fish and bacteria to protect recreation.
The $1.73 billion (City of Indianapolis, Department of Public Works (2008) plan is expected to reduce overflows
from 45 -801 imes pe r y ear t o t wo t o four t imes pe r y ear. A dditionally, t he City pi ans to i mplement watershed
improvement pr ejects c osting a n additional $6 4.3 m illion. T o reduce t he ov erflows t he pi an c ontains multiple
components. Major components include construction of a deep tunnel to capture overflows for treatment after peak
flows subside, new sewers to capture overflows and direct them to the tunnel, and construction of separate sewers
(City of Indianapolis, Department of Public Works, 2009 and 2006)
Demand Management Outreach
In 2005, Indianapolis's water system demands exceeded the system's capacity during a hot and dry period in the
summer for fourteen days. To r educe s trains on the water sy stem capa city V eolia E nvironement, op erator o f
Indianapolis's water supply system initiated an outreach program in 2006 to avoid a repeat of peak system demands in
summer months. Outreach included w ater conservation measures such as watering on odd/even days based on
addresses, install m oisture sens ors for i rrigation systems, use 1 ow flow de vices, and follow w ater us e advisories
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(Indianapolis Water, 2009). In 2006 with initiation of the outreach program, system capacity was only exceeded on
three days (Veolia Environment, 2009 and Indianapolis Water, 2009).
Midwest Agriculture
Farmers in the Midwest are beginning to look at watersheds as a whole and improve farming practices to reduce
downstream impacts. As a an area characterized by heavy agricultural upstream farming practices results in a range
of impacts from local water resource issues to negative impacts hundreds of miles below in the lower watershed and
Gulf of Mexico.
Water Reuse in Poultry Industry
Hudson Foods poultry facility located in Noel, Missouri was faced with a water purveyor that was having difficulty in
meeting the needs of the facility with existing water supplies. Hudson Foods initiated a four phase project to conserve
waterand reuse their extraordinarily quality effluent. Phase 1 involved reducing unnecessary water use, such as
educating employees and reducing excessive washdowns. Phase II involved modifications to the facility to reuse high
quality effluent in those areas that do not require potable water. Phase III encompassed using high quality effluent in
areas subject to U.S. Department of Agriculture (USDA) regulations. Recycled water use commenced in the screen
wash bars. S creen wash bar water does not contact products. P hase IV incorporates further use of high quality
effluent in areas subject to USDA regulation and development of database to illustrate the quality of the effluent as
compared to EPA National Primary and Secondary Drinking Water Standards. A goal of Phase IV is to allow use of
the high quality effluent in further processes subject to USDA regulation where potable water is not required and the
high quality effluent would not come in contact with product. It is estimated after final implementation of Phase IV,
72 million gallons of water will annually not need to be pumped from the local aquifer by the water purveyor. Other
benefits in elude im proved water q uality in the c ommunity f rom r educed pollutant d ischarge to the Elk River,
preservation of ground water supplies, and reduced operating costs. A pplications learned at the Noel facility have
been applied to three other Hudson Food facilities, including the use of effluent from a WW TP for washdown and
cooling water in a broiler plant, resulting in additional water savings of over 450,000 gpd (EPA, 2011).
Non-Point Source Pollution from Agriculture
Conservation and agricultural groups within the Mississippi River Basin have started an initiative to address water
quality and wildlife habitat throughout the basin and the Gulf of Mexico by targeting NPS pollution from agricultural
operations. F unded by M onsanto C orporation the i nitiative i s 1 ed by T he N ature Conservancy, Iowa Soybean
Association, and Delta Wildlife. The initiative will work with farmers to reduce nutrient and sediment loading in the
Mississippi River Basin. The National Audubon Society will work with residents to reduce NPS pollution in the
Basin and improve wildlife. P ilot studies will be conducted in various agricultural areas throughout the Basin to
improve farming pract ices t o likewise improve w ater qua lity and enhance w ildlife i n the B asin. P ilot prog rams
include B MP i nstallation and improvement prac tices de signed to improve t he he alth oft he Mi ssissippi R iver
ecosystem. Data re suits will be gathered and disseminated annually to farmers so they can apply the practices to
improve water quality and wildlife habitat. Results of the program are expected to be able to be integrated into other
major river m anagement p lans t hroughout the world. A dditionally, a M ississippi R iver F arm N utrient Working
Group will be formed to engage other organizations, industry-related groups, and other organizations in working with
experts improve the watershed (Environmental News Service, 2008 and The Nature Conservancy, 2008).
Rouge River National Wet Weather Demonstration Project
The R ouge R iver N ational We t W eather D emonstration Project in Michigan utilized a sy stematic w atershed
management appr oach to address w ater qu ality i mpacts from al 1 po llution sources and use i mpairments i n the
watershed. Applications learned in this watershed are being applied to other watersheds throughout the country and
are applicable to addressing water quality as it relates to TWM. The Rouge River Watershed is located in southeast
Michigan c overing a n area of a pproximately 438 square m iles, i ncluding a 11 or a po rtion of 4 8 m unicipalities.
Initially, the project began in 1992 and was joint effort involving federal, state, and local agencies narrowly focused
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on CSO control. A s the project evolved and early projects were implemented, monitoring indicated other pollution
sources were impacting the watershed, preventing watershed restoration, and water quality standards were still not
being m et. A w atershed-wide st rategy w as de veloped followed by de velopment of sev en subwatershed plans.
Subwatershed plans w ere de veloped t o identify st eps t o address ou tstanding w ater qua lity pr oblems inc luding
stormwater, C SOs, S SOs, failing s eptic t anks, and n on-point pol lution s ources. T hroughout pi an de velopment an
extensive public information and education program was developed emphasizing that downstream residents have the
right to expect clean water from upstream residents. In 2000, w ater quality monitoring indicated improvements to
date had resulted in the cleanest water in decades (The Rouge River National Wet Weather Demonstration Project,
2009a, b and c).
D.3.3 Northeast Region Strategies
Similar to the Midwest, water planning solutions in the Northeast tend to mainly focus on reducing peak loading to
sewers during storm events to reduce CSOs, SSOs, and achieve compliance with TMDLs with the notion of planning
for a combination of natural controls and large infrastructure source controls. To a lesser extent, solutions address
reducing cryptosporidium in drinking w ater sou rces, conservation, and water sy stem r eliability ha ve be en
implemented. Multiple innovative principals, such as housing all aspects of water management in one department,
integrated planning, and implementation of onsite wastewater recycling have been adopted in the Northeast and can
be applied elsewhere in the development of a TWM strategy.
New York, New York
The City of New York is dealing with multiple issues to alleviate problems associated with water quality and water
supplies. While N ew Y ork's w ater sup plies are relatively abundant, its w ater infrastructure sy stem i s agi ng and
requires repairs necessitating the need for improved reliability if portions of the system need to be taken off line.
Poor water quality in waterways is driving efforts to manage runoff as a means to improve water quality, but not as a
means to improve water supplies. New York has developed plans to address poor water quality in waterways, remove
cryptosporidium from sour ce w aters, maintain pure w ater so urces not r equiring f iltration, r educe i mpacts o f
suburbanization on watersheds, and ensure reliability of its water supplies by investigating innovative approaches.
P/flNYC
Beginning in 2006, New York City initiated a sustainable plan, PLaNYC, focusing on the five key aspects: land,
water, transportation, energy, air, and climate change. The water plan is divided into two plans, one for water quality
and one for the water network.
Sustainable Stormwater Management Plan 2008. The Sustainable Stormwater Management Plan 2008 component
of PlaNYC addresses water quality issues associated with TMDLs, CSOs, and SSOs. The overall goal of the plan is
to increase public access and use of waterways from the current level of 40-90% by 2030. A major target of the plan
is to enact policies within the next two years that will use source controls to capture an additional billion gallons of
stormwater ann ually. The i nteragency pi an seeks t o use sou rce controls, g reen infrastructure, low i mpact
development techniques, BMPs, green roofs, alternative roadways allowing infiltration, and rain barrels or cisterns to
reduce runoff. As stated in the plan, the most cost-effective option for stormwater control is to incorporate controls
into planned construction or reconstruction. N ew York City is leading the challenge by conducting demonstration
projects as a showcase to landowners and developers regarding costs, benefits, and feasibility.
A t hree pa rt s trategy ha s be en de veloped to m eet t he pi an g oal: implement t he m ost c ost e ffective an d feasible
controls, resolve the feasibility of pr omising t echnologies, and e xplore funding opt ions for source controls. Ten
initiatives have been developed:
Capture benefits of ongoing PlaNYC green initiatives - zoning amendments to requiring street trees and
green parking areas; planting am illion trees; green roof tax abatement; eng ineered wetlands in Bluebell
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system; conv ert asphalt f ields t o turf; conv ert school y ard areas into playgrounds; and pro tect n atural
wetlands
Continue with implementation of source control efforts - zoning amendments restricting pavement of
front yards; r equiring planting of g reen areas i n private ow ned pub lie p lazas; incentives f or w ater
conservation; coordination among agencies for construction specifications; use of High Level Storm Sewers;
and multiple measures to reduce flooding
Establishment o f n ew gu idelines for p ublic p rejects - release o ft he following manuals i ncorporating
cutting-edge stormwater management practices: Street Design Manual, Park Design for the 21st Century;
Sustainable Urban Site Design Manual, and the Water Conservation Manual
Adopt performance standards for new development in sewer regulation and codes
Improvements in notification of CSOs
Completion of ongoing demonstration projects and other studies - testing of source controls to determine
applicability to broader applications; develop answers to feasibility of source controls; mapping impermeable
surfaces throughout the City, and updating the soil survey for the City
Continue planning efforts for implementing promising source control st rategies - development of
designs an d identification off unding m echanisms f or s ource co ntrol strategies t hat can be i ncluded in
sidewalk standards, road reconstruction standards, green roadway infrastructure, and building performance
standards
Planning for maintenance of source controls - consideration of maintenance costs in initiatives
Establishment of new funding options for cost-effective source control - examine rate increases to water
and sewer charges, enact stormwater charges, or a combination of charges; use of the general fund;
investigate use of outside funding, federal funding f or i nfrastructure, or funds that would be expended for
conventional pollution control methods
Complete w ater and wastewater r ate studies and assess rates for stormwater services (City of New
York, 2008a).
PlaNYC R eport on W ater N etwork. To m aintain r eliability a nd dr inking w ater qua lity, N ew Y ork C ity ha s
developed a Water Network Report as part of PlaNYC. The report develops three strategies to ensure water supply
reliability: e nsure t he qu ality of dr inking w ater, c reate r edundancy for a queducts t o t he C ity, a nd m odernize t he
distribution network in the City. Initiatives developed to meet these strategies include:
Continuation of the watershed protection program - purchase additional land in watersheds; work with
farmers an d foresters t o develop sustainable p ractices; and repair s eptic systems w ithin water s upply
watersheds
Construction o f a ultra-violet (UV) disinfection pi ant for Catskill a nd D elaware w ater systems -
opening of largest UV disinfection facility in the world in 2012 to control cryptosporidium
Construction of the Croton Filtration Plant - suburbanization in the watershed has resulted in negative
impacts to water supply
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Launch a new water conservation effort - launch new rebate programs for toilets, urinals, high efficiency
washing machines in apartment buildings and Laundromats with the goal of reducing total water use for the
City by 5 % saving 60 MOD ; and evaluation of other programs including g ray water reuse, leak detection,
and water efficient industrial equipment
Maximize existing facilities - maximize s upply s ources t o reduce i mpacts of dr oughts a nd c onstruct
alternative connections to reservoirs
Evaluate new water supply sources - ensure adequate water supplies are available if Delaware Aqueduct is
required to be shut down for repairs by evaluating groundwater; water recycling for steam, toilets, or air
conditioning; c apture a nd c ollect g roundwater c urrently di sposed o f from s ubway sy stem and clean it for
potable use; regional interconnections; and new infrastructure
Complete water tunnel No. 3 - to provide system redundancy to complete repairs in aging infrastructure
Complete b ack-up w ater tunnel to S taten I sland - Army C orps o f Engineers dr edging ha rbor and w ill
remove existing back-up system
Increase pace of upgrades to water main infrastructure - increase pace from 60 miles of upgrades per
year to 80 miles per year (New York, 2008 b and c).
Solaire Apartments Dual Plumbing
The Soliare Apartments in New York are an example of a dual plumbed building using onsite recycled wastewater for
toilet flushing and cooling towers. C ollected stormwater is used for irrigation purposes. P otable water demand is
75% less than a comparable single plumbed 380 unit apartment building. Completed in 2003, the building contains
the first onsite wastewater treatment system in a multi-family building in the U.S. Water savings are estimated 9,000
gpd for toilet flushing, 11,500 gpd for cooling towers, and 6,000 g pd for irrigation. The building is a LEED gold
building (GE, 2006 and Cosentini Associates, 2009).
Philadelphia, Pennsylvania
Philadelphia Water Department, which manages stormwater, drinking water, and wastewater within Philadelphia, has
embarked on a watershed based methodology using a balanced "land-water-infrastructure" approach to control CSOs.
The D epartment us es a n integrated r egional w atershed pi anning a pproach e mphasizing a daptive m anagement t o
appropriate balance of each approach. Each component is balanced to achieve an overall solution to control CSOs.
Land i s focused on s ource c ontrol, w ater on e cosystem r estoration, a nd i nfrastructure on c apital i mprovement
projects. The overall goal is to minimize the introduction of runoff into the sewer system.
The land or wet weather source control portion of the approach involves a variety of structural and non-structural
measures and low i mpact de velopment t echniques. P hiladelphia enacted new pos t-construction r egulations for
development and redevelopment in 2006 to achieve a natural balance between runoff and infiltration rates. Projects
can achieve compliance with the regulations through land-based practices designed to use natural processes such as
redirecting runoff to pervious green areas, onsite bioretention, subsurface storage of runoff, infiltration, green roofs,
swales, and tree canopies. Planned low impacts development programs for the Department's service area include:
Large scale street tree program for aesthetics and improvement of stormwater at the source
Incentives for preservation of open space for use of stormwater management at the source
Incentives and requirements to manage stormwater on private property and streets in a green manner thereby
reducing sewer demands
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Implementation of stormwater management on publ ic lands and streets reducing in a green manner thereby
reducing sewer demands.
Ecosystem restoration or the water portion of the approach utilizes projects to restore aquatic ecosystems impacted by
CSOs. Typical projects include bank stabilization, creation of aquatic habitat, fish passage improvements, removal of
plunge pools, stream bed stabilization, riparian buffer creation, and enhancing wetlands.
The Capital Improvement Program approach is used to construct C SO infrastructure to reduce CSOs. Projects
include s torage, conveyance, and treatment f acilities. I n som e cases i t i s more cos t-effective t o construct
infrastructure projects in conjunction with the other approaches (Philadelphia Water Department, 2009).
D.3.4 South Region Strategies
Unlike the Midwest and Northeast but similar to the West, water supplies are more constrained in the South as a result
of climate, increasing populations, and drought. Water resources agencies in the South have had the need to expand
their water supply portfolios to include innovative solutions such as extensive recycled water use, indirect potable
recycled water reuse, and a strong emphasis on water conservation. For example, Florida has tapped recycled water
as a m ajor w ater source i n cities and districts ac ross t he s tate (Florida D epartment of E nvironmental P rotection,
2009). While the area does not have as widespread of an issue with CSOs and SSOs, compliance with water quality
issues still remains a challenge. Typical BMPs and LID are used to retain and treat stormwater throughout the region.
Integrated planning in some areas has embraced TWM at the watershed level to maximize water benefits in a cost-
effective manner. This section highlights some of the more notable solution applicable to TWM and approaches used
to incorporate TWM into the planning process.
Total Water Management in the South
In the South where water is less plentiful than the Mid-west and Northeast, TWM has been incorporated into long-
range i ntegrated w ater resource planning i n m ultiple a reas. Two e xamples of e fforts i n G eorgia a nd F lorida a re
highlighted.
Total Water Management: Clayton County Water Authority, Georgia
Clayton County Water Authority (CCWA) has implemented at TWM strategy into its planning processes as it was
faced with a multitude of constraints, requirements, and demands. Within its service area water and sewer demands
are attributed to popu lation growth, however, w ater s upply s ources a re constrained due to w ater conflicts a nd
wastewater d ischarges are i mpacted by T MDL requirements. The A uthority first app lied TWM dur ing i ts 20 00
planning process and further refined it in its 2005 planning cycle. A desired outcome using the TWM process was to
maximize i ts w ater supply por tfolio a nd a chieve c ompliance with both federal a nd s tate r egulations w hile
simultaneously meeting customer service goals in a cost-efficient manner.
TWM has already provided the Authority with multiple benefits. During the recent drought in Georgia, a 200 d ay
water supply was maintained at all times without compromises to water quality both in the watershed and in the water
system. D rought proofing of water supplies has occurred with indirect reuse oft reated wastewater by increasing
reclaimed water recharge to its water supply reservoirs via a constructed wetland treatment system from 10 MGD to
26 MGD. Utilization of reclaimed water allowed reservoirs to remain at near full capacity during the recent drought.
As a direct result of TWM, the Authority now includes stormwater and watershed management for the entire county
as part of its management responsibilities allowing for control of water resources by one agency that can manage all
aspects of water in a reliable, economical, and sustainable manner (Jeffcoat, et al, 2009).
St. Johns River Water Management District, JEA, and Clay County Utility Authority
TMDLs and water quality i ssues are driving efforts in the St. Johns River Water Management District to improve
water quality and develop long-term reliable water supplies. The District is assisting water and wastewater utilities in
meeting t hese g oals. The di strict launched a multi-media Water C onservation P ublic A wareness C ampaign a long
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with more than 20 utility partners (Wilkening, 2007). By maximizing water reuse JEA (a local utility) and the Clay
County Utility Authority are seeking to offset potable water demands and achieve nutrient discharge requirements for
wastewater. Both agencies integrated TWM into their master planning processes. Elements of the approach used
include:
Stakeholder identification of project goals and objectives - 1) comply with TMDL requirements 2) Reduce
potable water use 3) Identify opportunities for water reuse
Collection and analysis of data - for each service area collect date for 1) potable water supplies 2)wastewater
production 3) reuse demand
Utilization of decision-support software (VOYAGE model) to identify project meeting project objectives
Output of the approach resulted in the identification of least-cost alternatives that met project objectives. Modeling
additionally indicated excess wastewater within JEA's service area could satisfy reclaimed water demands in Clay
County service area (Patwardhan et al., 2008).
Dual Distribution Systems
Dual di stribution systems can provide m any adv antages t o municipalities; sp ecifically i n the c ase w here sm all
distribution lines are used for potable water service, and separate non-potable distribution lines are used for fire flow
and irrigation. W hile potentially feasible in new developments, retrofits to existing developments tend to be less
economical. By utilizing smaller potable water lines, smaller volumes of water are being transported, resulting in the
following advantages:
Reduced degradation of water quality in the distribution system prior to reaching the customer
Reduced chlorine dosing at the water treatment plant resulting in a lower disinfection by-product formation.
Increased velocity of water through smaller pipelines when compared to typical pipe sizes, resulting in less
static water, and less biofilm growth (Okum, 2005).
Two examples of proposed dual distribution systems in the South are in St. Petersburg, Florida and in the service area
of S outh M artin R egional A uthority i n F lorida. I n C hatham C ounty, N orth Carolina a study w as initiated to
determine the feasibility of a dual system in comparison to a traditional system as discussed in the following section.
Chatham County, North Carolina
Briar Chapel, a proposed master-planned community in Chatham County, North Carolina, was the subject of a case
study analyzing the costs and benefits of three options for a dual water distribution system (reclaimed and potable) for
phase one of the development. Phase one of Briar Chapel consists of 350 single-family homes. One option was a
traditional water distribution system where fire flows are included in the potable distribution system. Option A was a
dual system using reclaimed water for landscape purposes. O ption B was a dual system using reclaimed water for
landscape and toilet flushing. Options A and B both include fire flows as part of the non-potable distribution systems.
Each of the options was modeled using EPANET2 using multiple assumptions.
Results of this case study indicate at this development multiple benefits could be achieved. Length-average pipe
diameter for the traditional system was 8.6 inches. With Option A this was reduced to 4.4 inches and further reduced
to 2.8 inches with Option B. Average water residence times were reduced from 16.5 hours to 4.4 hours for Option A
and 3.8 hours for Option B. As indicated in the cost study capital costs require further refinement. In general, capital
costs associated with the pipe network of the di stribution systems are greater for Options A and B . O ffsets are
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available for the use of smaller decentralized wastewater facilities associated with Options A and B and may reduce
the cost differences (Digiano et al., 2009).
Decentralized Water Recycling Systems in the South
Provided below is a listing of satellite treatment facilities within the South. This listing is not intended to be a
comprehensive listing. If available, the distance from the satellite treatment facility to the point of use versus the
distance from the closest WWTP to the point of use, is provided:
Cauley Creek, Georgia (5 MGD)
Oak Island, North Carolina (0.4 MGD)
Midland, Texas (0.1 MGD) - 1 mile from point of use vs. 6 miles from closest WWTP.
Indirect Potable Reuse Projects
Planned indirect potable reuse of reclaimed water occurs in multiple locations throughout the South. A few of the
major facilities are highlighted here.
El Paso Water Utilities, El Paso, TX
Hueco Bolson Recharge Project
Injection of treated wastewater into aquifer for withdrawal as part of drinking water supplies. Also used for
industrial and irrigation purposes.
Production: 8,400 AFY
In operation since 1985
IWVA, Lawrenceville, GA
F. Wayne Hill Water Resources Center
Treated wastewater u sed for irrigation w ith e xcess di scharged to C hattahoochee R iver, pe nding further
approval may potentially be discharged to Lake Lanier a water supply source for Atlanta
In operation since 2000, expanded 2005
Design Capacity 67,424 AFY (Australian Capital Territory, 2009)
Upper Occoquan Sewage Authority, Fairfax County, VA
Upper Occoquan Project
Discharge of treated wastewater to Occuquan Reservoir, which is used for drinking water supplies; at times
has accounted for 4/5 of flow into reservoir
In operation since 1978
Production: 32 MGD expanding to 54 MGD, tripling its original capacity (in progress)
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Regional Water Planning
Regional water planning is used in the south to make water decisions at the larger regional levels. Regional water
planning efforts for Florida and Texas are provided as examples.
Florida
Florida h as formed five w ater m anagement di stricts tasked with managing w ater r esources i n the state under the
Department of Environmental Protection. Each district is highly involved in all water management issues within their
individual boundaries. Districts perform the following functions:
Develop water management plans for water shortages
Acquire and manage lands related to water management purposes
Manage consumption of water, aquifer recharge, surface water, and well construction
Administer stormwater management programs
Assist with development of water elements in local government comprehensive plans.
The structure of these districts and interaction with local governments and utilities allows for the districts to assist
local g overnments a nd u tilities w ith integrated p lanning i n w atersheds ( Florida D epartment o f E nvironmental
Protection, 2009).
Texas
The Texas Water Development Board has divided Texas into 16 planning regions to develop regional water solutions
in a cost-effective manner. Regions are required to develop regional water plans. Each regional water plan seeks to
determine the following:
Water demands
Water supplies for drought use
Areas of surpluses and needs for additional supplies
Social and economic impacts if water demands not met
Identify ecologically unique waterways
Identify sites for reservoir construction
Coordinate with neighboring regions
Propose recommendations to improve water resource management in Texas
Identify strategies to meet future demands in the next 30 years and in the next 30 to 50 years
Identify where no feasible solutions exist to meet demands (Texas Water Development Board, 2009).
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Southwest Florida Water Management District Stormwater Reuse
As proposed Southwest Florida's Water Management District's recycled storm water project consists of diverting
stormwater through an alternative outfall from the Venice Golf and Country Club to a Sarasota County operated pond
for irrigation needs. Use of stormwater for irrigation needs at the golf course will allow other users access to 349,000
gpd of reclaimed water currently used by the golf course. Capture of the stormwater runoff will reduce nutrients in
surrounding w aterbodies and w ill allow nu trients conveyed i n s tormwater t o be r eapplied to the g olf c ourse.
Estimated c onstruction c osts a re a pproximately $165,512 dol lars i n 2005 dollars (Southwest F lorida W ater
Management District, 2005).
D.4 Regulatory Constraints
Regulatory constraints impacting TWM vary from state to state. S tates have adopted regulations based on needs.
Water quality regulations associated with surface waters, such as CSOs, SSOs, and TMDLs are mandated by the
federal government with enforcement and administration of the regulations typically at state levels. Water use
regulations are developed at the State and local levels. States in the South and West have been at the forefront of
adopting r egulations t o s afely e xpand w ater supply portfolios t o i nclude non -traditional op tions. I n m any s tates
innovative solutions may require new or revised regulations.
D.4.1 Reclaimed Water for Fire Protection
Currently, guidelines or regulation for the use of reclaimed water for fire protection exist in only nine states: Arizona,
California, Florida, New Jersey, Hawaii, North Carolina, Texas, Utah and Washington. Each of these nine states also
allow t oilet flushing us ing r eclaimed w ater, thus n ew de velopments c ould realize t he be nefits from ha ving dua 1
distribution s ystems t hatt ake a dvantage of us ing r eclaimed w ater i ndoors f or toilet f lushing. E xtensive
implementation of reclaimed water for fire flows also must overcome the hurdle of receiving the support of firefighter
unions (Digiano et al., 2009).
D.4.2 Rain Collection and Water Rights
Regulations regarding the collection and use of rainwater onsite vary by state. LID and BMPs, such as rain barrels
and cisterns, used to capture and retain water onsite for use are not legal in every state. Colorado and Utah are the
only western states that do not allow the collection of rainwater. The following provides a summary of a few state
regulations:
Colorado - In Colorado rain falling on private land does not legally belong to the landholder, but belongs to
those downstream hoi ding pre-emptive water rights. However, Coloradans have passed a bill that allows
certain homeowners to capture and use roof runoff (Colorado Division of Water Resources, 2010).
Arizona - Individual i ncome t ax credits o f 25 %, u p t o $1,00 0, a re offered t o offset the c ost o f a r ain
harvesting system
New Mexico - In Santa Fe County cisterns are required on all commercial building and for houses exceeding
2,500 sq ft. Houses smaller than 2,500 sq ft must have swales, berms, or rain barrels to harvest the rainwater.
Utah - All r ainwater 1 egally be longs to the st ate. L egislation is pr oposed to al low r esidents t o harvest
rainwater
Washington - Laws regarding rainwater harvesting are not clear, thus the state does not enforce regulations
that could potentially regulate rainwater harvesting (Riccardi, 2009 and McCausland, 2009).
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D.4.3 Gray Water Regulations
Similar t o other w ater us e r egulations, gray w ater r egulations ar e d eveloped at st ate 1 evels. R egulations v ary
differently by state with some states, such as Arizona and New Mexico, with regulations that are more amenable to
gray water systems. Other states, such as California and Utah, increase the difficulty in installing gray water systems.
Arizona's regulations are an example of a tiered approach with requirements based on system sizes. Arizona has
taken a three tiered approach to regulating gray water systems based on system size:
First Tier: Residential less than 400 gpd and meeting list of requirements - covered under general building
permit
Second Tier: Residential over 400 gpd or commercial, multi-family, and institutional systems, or systems not
meeting list of requirements - requires a standard permit
Third Tier: Any system over 3,000 gallons a day - considered on an individual basis.
New Mexico has based its regulations on Arizona's approach (Oasis Design, 2009).
D.4.4 Recycled Water Use Regulations
Recycled water use is regulated at the state, regional, and local levels. Regulations differ a cross the country with
California and Florida in the forefront of encouraging recycled water use. The greatest concern relates to the potential
for cross-connections between the potable and reclaimed water plumbing systems, and water quality of recycled water
that i s us ed f or g roundwater r echarge. A s of J anuary 1, 2008 C alifornia a Hows dua 1 pi umbing i nstallation i n
condominiums. P revious uses of dual plumbing in California were limited to apartments and other non-residential
uses w here t he po tential for cr oss-connections a re 1 imited a s bui Iding ow ners controls m aintenance o f p lumbing
systems. In California, regional water quality control boards have made it more challenging to use recycled water for
groundwater rechargeeffectively requiring advanced treatment using reserve osmosis and membranes.
EPA has developed a summary of water reuse regulations by state, and offers guidelines on implementation of water
recycling (EPA, 2004).
D.4.5 Impact of Plumbing Codes on Water Conservation
In multiple cases, current plumbing codes can interfere with adoption of new water conserving fixtures. Plumbing
codes vary at the local, regional, and state levels dependent upon the location and the code adopted. T hree major
areas commonly impacted by plumbing codes include hot water distribution losses, shower efficiency, and waterless
urinals.
Currently, codes allow water waste related to hot water demands as people allowing cool water to flow out of the
fixtures until hot water reaches the fixture. Reducing this waste of water can be achieved by placing limits on the
diameter and length of hot water pipes, insulating pipes, and requiring utilization of on-demand recirculation systems.
Showerhead efficiency i s r egulated by t he F ederal E nergy P olicy A ct limiting the m aximum f low r ate of a
showerhead to 2.5 g allon per minute. H owever, this r equirement does not regulate the num ber o f s howerheads
installed in a single shower, provide for a maximum flow rate for all heads in a single shower, or establish a minimum
spacing between showerheads.
Regulations o f waterless urinals vary dependent up on the adopted plumbing code used by a regulatory agency.
Recent version of the International Plumbing Code allow the installation of waterless urinals, but other codes such as
the U niform P lumbing C ode (UPC) do no t m ention t he us e o f w aterless ur inals. I nterpretation of the 1 ack of
specifically mentioning the device in the UPC is interpreted differently among agencies. Some agencies believe that
since the device is not mentioned, it does not comply with the UPC (Pape, 2008).
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A study by Dickinson et al. (2003) forecasted reductions in water production due to adoption of a national plumbing
code, 5% in 2010, increasing to 8% water savings by 2020 (base year of study 1999). Estimated utility savings were
$26 per person which equates to $7.5 billion nationwide in reduced infrastructure costs.
D.5 Innovative TWM Strategies at the Global Level
Throughout the world innovative TWM strategies have been developed to address water quality and water supplies
problems. In many cases countries have developed progressive solutions such as "sewer mining"(tapping into a
sewer and withdrawing wastewater flows for treatment and recycled water use) in Australia, and direct potable use of
recycled water in Namibia.
D.5.1 Windhoek, Namibia
Windhoek, N amibia i s t he e conomic c enter of N amibia 1 ocated i n t he C entral H ighlands w ith a popul ation o f
approximately 213,000 people in 1998. Population growth was approximately 5.44% per year between 1991-1995.
Water resources include three surface reservoirs located on ephemeral rivers, groundwater and reclaimed water. The
nearest y ear ar ound waterway i s 1 ocated 700 kilometers aw ay. S ince 1968, Windhoek ha s sup plemented potable
water directly with recycled water. Rainfall averages 360 millimeters (14.17 inches).
Integrated Water Demand Management Planning
As a result of water production increasing by 13.5% during 1990-1991 related to an influx of people from rural areas
and high population growth, it was determined demands would eventually outstrip supplies. In 1994 an integrated
water demand management policy was approved by the City Council for implementation over a five-year period using
least cost planning. The planning process required investigation of unconventional water sources. A severe drought
in 1996 resulted in immediate implementation of the entire plan. Policies adopted include:
Tier tariff system - a block system reflecting the true cost of water and to reduce excess usage
Maximum reuse of water - use of semi-purified effluent for irrigation; expansion of the direct potable water
reuse facility; and graywater reuse on private property
Reduce plot sizes and increase densities - residential plot sizes in new developments were decreased; increase
densities in urban areas to allow two house per lot; and in older sections of the City allow implement re zoning
to businesses and townhouses
Guidelines for urbanization development
Reduction of municipal water use - reduce consumption of water by 50% in municipal gardens
Wet industries - provide wet industries with guidelines for efficient water use on a continuous basis and new
wet industries required to reuse water
A public outreach campaign was coupled with the adopted measures, new water conservation measures, and technical
requirement. Technical requirements included:
Lowering una ccounted w ater u se - conduct 1 eakage de tection on a c ontinuous ba sis, i mplement r epair
programs, conduct water audits, manage meters, implement pipe replacement program
Efficient ways of w ater gardens - irrigate municipal gardens with proper systems and advise gardeners on
water efficient irrigation systems
Artificial recharge of Windhoek aquifer - investigate and implement natural and artificial recharge of aquifer
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Rainwater harvesting - implement rainwater harvesting program.
Numerous successes have resulted from implementation of the plan. Overall, the plan has resulted in postponement
of major water infrastructure projects for at least ten years and an annual savings $13.54 m illion (1998, Namibia).
Water reliability during drought periods has increased with groundwater recharge. Daily per capita residential use has
decreased from 201 liters in 1990/91 to 117 liters in 1996/97 (Merwe, 2009).
Direct Reuse of Recycled Water
The New Goreangab Water Reclamation Facility, operated by Windhoek Goreangab Operating Company Pty Ltd.
and located in Windhoek, Namibia, is an example of a facility where recycled wastewater t reated with advanced
treatment is d irectly delivered i nto t he pot able w ater di stribution s ystem w here i t bl ends w ith ot her w ater s upply
sources. As summarized in a compilation of recycled water facilities throughout the world, the facility located in
Windhoek, Namibia t ypically de livers a b lend of 35 % recycled t o 65 % potable water for hum an consumption.
During low water demand month in the winter season, a blend of 50% recycled to 50% potable water is distributed.
Currently, 6, 160 A FY o f r ecycled w ater a re pr oduced in the facility ope rating s ince 2002 ( Australian C apital
Territory, 2009).
The facility uses the following treatment technologies to treat secondary effluent: powdered activated carbon, acid,
polymers, pre-ozonation, coagulation/flocculation, dissolved air flotation, rapid sand/anthracite filtration, ozonation,
biological activated carbon filtration/adsorption, granular-activated carbon filtration, membrane ultra-filtration, and
chlorination/stabilization. P roduct water is continuously monitored. If preset water quality parameters are not met,
then the water is recycled through the facility again. To prevent the mixing of household wastewater and industrial
wastewater, industrial wastewater is collected and treated separately w ith the end product used for irrigation only
(Australian Capital Territory, 2009 and Lahnsteiner, 2005).
D.5.2 Singapore Public Utilities Board, Singapore
Singapore's Public Utilities Board had developed an integrated approach to water management to promote sustainable
development, boost economic development, and enhance the urban quality of life by ensuring adequate water supply,
controlling flooding, and providing water-related recreational and cultural opportunities.
Stormwater Runoff Reuse
Since 1985 the Bedok-Seletar project has captured stormwater runoff from a 5,000 hectare area for use as a raw water
source. Runoff is captured both directly and indirectly. R unoff is e ither intercepted a series of di version poi nts,
stored, and then pumped into a reservoir or runoff is captured and directly conveyed to a reservoir (COM, 2009a).
In 2008, the Singapore Marina Barrage project was completed consisting of a 1,000 foot long barrage or dam acting
as a tidal barrier to prevent high tides from flooding inland areas while creating a freshwater reservoir behind the dam
through natural flushing. The project provides three main benefits:
Water supply - isolating a river outlet to provide an additional source of raw water to bolster drinking water
supplies by impounding 35 MGD of urban runoff per day
Flood control - providing protection from high tides for low lying inland areas
Quality of life improvements - linking the central business district with a recreational and visual attraction of
the Marina Basin.
Normally, the dam gates will remain closed, however during extreme storm events when the tide is low the gates will
be raised to release excess flows. Under high tide events and during extreme storm conditions a pump station with a
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capacity of 5,400 M GD will pump excess water to the ocean. A small boat hoist was constructed as part of the
barrage to allow the occasional movement of boat traffic between the Marina Reservoir and ocean (CDM, 2009a).
Indirect Potable Water Reuse
Four NEWater Plants operated by the Singapore Public Utilities Board produce reclaimed water for indirect potable
reuse utilizing a three step process, microfiltration, reverse osmosis, and ultraviolet light. A contract for construction
of a fifth plant was awarded in 2008. Approximately 20 MGD of water are produced from the four plants. Reclaimed
water is used for irrigation, air cooling towers, bottling, and industrial uses, as well as blending with drinking water in
raw water supply reservoirs. Raw water from the reservoirs undergoes conventional water treatment prior to entering
the potable distribution system. Approximately, 1% of the total daily water consumption in Singapore (3 MGD) is
derived from reclaimed water. In 2011, this percentage is planned to increase to 2.5% in 2011 (Singapore Public
Utilities Board, 2009).
D.5.3 Other Indirect Potable Water Reuse Projects
Planned i ndirect po table reuse o f reclaimed w ater o ccurs i n m ultiple locations t hroughout the w orld. O ne of t he
major facilities is the IWVA facility in Wulpen, Belgium. In ope ration s ince 2002, the Wulpen Aquifer Recharge
Project located in Wulpen, Belgium utilizes reclaimed water for groundwater replenishment in groundwater basins
designated for drinking water source (Australian Capital Territory, 2009).
D.5.4 Seawater Desalination in Israel
To meet consumer demand for water in a dry climate, Israel constructed the world's largest desalination plant, the
Ashkelon Desalination Plant. Commencing operation in 2005, the facility converts approximately 26 billion gallons
of sea water to potable a year. The facility s upplies 5-6% of Israel's potable water demand and meets 13% of
consumer de mand. T o improve ene rgy efficiency, the facility i ncorporates energy r ecovery de vices d esigned to
collect pressurized brine (Water-Technology.Net 2009).
D.5.5 Dual Plumbing
Seawater Toilet Flushing, Hong Kong
To conserve potable water after a severe drought in the 1960's Hong Kong embarked on using seawater for toilet
flushing (Tang, 2007). Approximately 80% of the 6.8 million people in Hong Kong use seawater for toilet flushing
which reduced potable water demands by approximately 20% and equated to 241 million m3 in 2003. Hong Kong is
continuing to look at applications for the use of seawater in lieu of potable water, such as use in air conditioning
systems and seawater desalination.
The seawater system is relatively simplistic with limited treatment consisting of screening and disinfection. Seawater
is withdrawn directly from the sea, treated in the pump stations, pumped to surface reservoirs, and then into the
seawater distribution system. Corrosion is avoided with the use of polyethylene or polyvinyl chloride pipes.
Advantages of the system are summarized below:
Unlimited resource
Seawater quality and aesthetics are dictated by regulations
Reductions in potable water demands
Single water supply system would be approximately 39% more expensive than a dual system
Disadvantages of the system - and remedial actions - are:
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Cross connections - adoption of standard procedures to prevent cross-connections
Corrosion o f pi pes and d eterioration o f c oncrete and w indow frames from 1 caking w ater - use of non -
corrosive pipes and improving water quality of supply reservoirs
Deposits and growth in p ipes leading to aesthetic complaints - use of regular flushing to remove algal
accumulation and electro-chlorination to control marine growth
Ecology problems - in rural areas wastewater is treated by septic tanks and discharged to rivers thus the use
of seawater in these areas can impact the salinity of the rivers
Treatment process for mixed freshwater and saltwater sewage - typical treatment systems have been modified
to deal with increased salinity of mixed waste sources
Chlorination - use of electro-chlorination process to reduce biological growth
Seawater quality can suddenly deteriorate leading to complaints and stains in toilet bowls - marine water
quality meets toilet flushing requirements most of the time, but existing treatment process cannot guarantee
turbidity of flushing water.
Australia
In Australia, reclaimed water is provided to single-family residences for indoor toilet flushing and for outdoor use,
including hose bibs, with thousands of additional new residences to be constructed in the near future. Dual plumbing
in Australia can also include hookups for washing machines.
After experiencing a severe drought in the early part of the decade, Australia has encouraged the use of recycled water
for residential purposes. In the Rouse Hill residential development over 16,000 single-family residences have dual
plumbing for toilet flushing and outdoor irrigation resulting in a potable water savings of approximately 35 % per
since 2001 (Urban Ecology Australia, 2009). In summer months demand commonly outstrips the supply resulting in
the need to add potable water to the system. On average 15% of the non-potable supply is potable drinking water.
Yarra Valley Water Ltd. (2011) in Victoria estimates dual plumbing for toilet flushing and outdoor irrigation at signal
family residences reduced potable demands by 45-50% and estimates additional plumbing costs of $2,000 (Australian
dollars) per unit. An additional $3,000 dollars is charged to developers per lot for recycled water use, $1,000 for dual
delivery pipes (before the service connection) and $2,000 for the recycled water plant and associated appurtenances.
The Pimpama and Coomera suburbs located south of Brisbane are undergoing tremendous growth and in response
will be required to have three water systems for residential use, drinking water, rain water, and recycled water. A
current population of 15,000 people is expected to increase to 120,000 by 2056. As a result all new developments are
proposed to be dual plumbed to reduce potable water demands by up to 84%. Homes will be dual plumbed to receive
recycled water for toilet flushing. Additionally, rainwater t anks will serve bathrooms, laundries, and hot water
systems. Drinking water will be plumbed only to kitchens. Gold Coast Water, the local water provider has launched
an extensive educational campaign for plumbers in the region (Gold Coast City Council, 2009).
A relatively new process in recycled water use, "sewer mining" (Sydney Water, 2009), is also occurring in Australia
to supply locally treated recycled water for dual plumbing systems. "Sewer mining" as defined by Sydney Water is
"the process of tapping directly into a sewer and extracting wastewater for treatment and reuse as recycled water."
Sewer mining ope rations can be privately owned which should spur competition. In Sydney Water's jurisdiction
sewer mining operations are first-come first served to prevent upstream extraction of an existing facility if it would
impact the volume of wastewater required. Multi-family residential projects, such as Discover Point in Sydney (Waste
Management & Environment Media Pty Ltd., 2011), are t reating w astewater onsite beneath the project for toilet
D-32
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flushing and irrigation. Excess water will be sold to irrigate an adjacent sports field. The recycled water portion of
the project capital costs is approximately $3.5 million (Australian dollars) and is expected to reduce potable water use
in the building by approximately 35%.
Table D-5 summarizes examples of dual plumbing in Australia.
Table D-5
Dual Plumbing Installation Examples in Australia
Location
Rouse Hill, Australia1
Yarra Valley Water,
Victoria2
Pimpama and
Coomera Suburbs,
Australia3
Discover Point,
Sydney, Australia4
Recycled Water Use
16,000 single-family
residences, outdoor use
and toilet flushing
Toilet flushing and
outdoor irrigation
Recycled water for toilet
flushing, rainwater for
bathroom, clothes
washer, and hot water
Sewer mining operation
to be used for toilet
flushing and irrigation
with excess water sold to
adjacent sports fields
Potable Water
Savings
35% (demand
exceeds supply in
summer requiring 15%
of supply to be
potable)
45-50%
84% (Forecast)
35%
Cost Range
N/A
$2,000 per unit
(Australian)
incremental cost for
dual plumbing; $1,000
per unit for delivery
pipes, $2, 000 for share
of treatment plant
N/A
$3.5 million
(Australian) for
recycled water
treatment
1. http://www.urbanecoloqv.orq.au/topics/waterrecvclinqrousehill.html and http://www.qoldcoastwater.com.aU/t qcw.asp?PID=5894
2. http://www.vvw.com.au/vvw/qroups/public/documents/content/vvw000781.pdf
3. http://www.qoldcoastwater.com.aU/t qcw.asp?PID=5885
4. http://www.svdnevwater.com.au/SavinqWater/RecvclinqandReuse/RecvclinqAndReuselnAction/SewerMininq.cfm and
http://www.wme.com.au/cateqories/water/dec4 OT.php
D.5.6 Water Tanks in Australia
Australia has extensive experience with the use of water tanks to collect rainwater from roofs for outdoor water use,
toilet flushing, w ater he ating, c ar w ashing, s pas and ponds , c lothes w ashing s wimming pool s, a nd fire fighting
(Australian Government, 2004). Indoor non-potable water use requires installation of dual plumbing. Water tanks
are comparable to cisterns and are installed above or below ground. Water is captured via rain gutters and is screened
before draining into water tanks. Water tanks connected to non-potable indoor water uses provide maximum use of
collected water as water collected during storm events is used immediately providing additional capacity in the tank.
Over 17% of Australian households have water tanks. Currently most new developments are required to install water
tanks.
Sydney Water has given out over 30,000 rebates to its residential and business customers saving approximately 317
million gpy. Rebates for residences and businesses vary depending upon tank size and ultimate use of stored water
ranging from $150 to $1,500. Public and private schools can receive up to $2,500. Table D-6 provides current rebate
amounts in Australian dollars.
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Table D-6 Water Tank Rebates for Sydney Water1
Qualifying Items
2,000-3,999 Liter Water Tank
4,000 - 6,999 Liter Water Tank
7,000 + Liter Water Tank
Water Tank Connected by Plumber to Toilet
Water Tank Connected by Plumber to
Washing Machine
Schools
Rebate Amount2
$150
$400
$500
$500
$500
$2,500
1. http://www.sydneywater.com.au/savingwater/lnYourGarden/RainwaterTanks/
2. All dollars are Australian dollars
Program requirements stipulate that all installations are required to meet building codes and local requirements. All
plumbing must be installed by a licensed plumber. Tank sizes can vary, but Sydney Water recommends a 5,000 liter
tank if the tank will supply all non-drinking water uses and a 2,000 1 iter tank if the tank will supply water for toilet
flushing and a small garden. Rebate amounts cannot exceed the cost of the water tank and installation. Eligible costs
include delivery, installation, gutter and roof pipe installation, foundation for above ground installation, excavation
for below ground installation, backflow prevention, flow regulator, first flush de vice, screens a nd g uards, extra
plumbing, pump, and piping to top off tank. Rebates are not issued for buildings required to install water tanks.
Program r equirements for schoo Is h ave add itional requirements. A 11 s chools app lying m ust com plete a w ater
education program, participate in a water conservation program, install a minimum of a 10,000 liter tank, and the tank
must be connected to fixed irrigation and/or toilet supply water.
A benefit of installing a water tank is that mandatory water restrictions do not apply to locations with a water tank as
long as long as the source of the water is the tank and the tank is not topped off with potable water (Sydney Water,
2009).
A study completed in 2007 by Marsden Jacob Associates, The Economics of Rainwater Tanks and Alternative Supply
Option, presented num erous e xtensive findings r egarding w ater tank cos ts an d associated economic i mpacts i n
comparison to alternative water supply sources. The study concludes water tanks could defer acquisition of future
water supply resources among other environmental benefits. Throughout Australia a 5,000 liter tank installed usually
costs between $2,500 and $3,500 including connections to plumbing.
Costs were developed in the study for a typical installation and on a yield basis. On average in Australia a 5,000 liter
tank installed usually costs between $2,500 and $3,500 including connections to plumbing. C osts per m3 of water
captured were developed in the study for areas across Australia. C osts were determined by dividing the annualized
capital and O&M costs by expected annual yield. Costs ranged between $2.15 and $12.30 per m3 of water. The wide
range in costs per yields is dependent on local climate conditions, tank size, and roof size. Lower range costs were
associated with buildings having greater roof sizes. Lower range costs are less than or comparable to yield costs
associated with other water source options under investigation in Australia. Higher end costs are as high as or higher
than most alternative water supply options under consideration. H owever these yield cost ranges do not take into
consideration the sav ings associated with reductions i n stormwater i nfrastructure sy stems, potential r eductions in
water main sizes, carbon impacts, and reduction in pollutants conveyed in stormwater (Marsden Jacobs Associates,
2007).
D-34
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D.5.7 Graywater Use in Canada
The Canada Mortgage and Housing Corporation has completed extensive studies in the use of graywater for reuse in
toilet flushing in residential and non-residential settings. In Vancouver, a 20-unit a partment bui Iding, Q uayside
Village, is being constructed as a demonstration project featuring graywater for toilet flushing. Each unit will collect
light and dark grey wall from all plumbing fixtures, except toilets, for reuse as toilet flushing water. Dual plumbing is
provided in the units to toilets and showers. Showers were dual plumbed in case future use is feasible. An onsite
wastewater treatment system uses a settling tank, biofilter, pre-ozonation, multi-stage sand filtration, and ozonation to
treat the graywater. Toilet wastewater and excess graywater is discharge to the sewer system. Capital costs were
approximately $115 ,000 (Canadian) w ith a n e stimated m onthly m aintenance c ost o f $100 ( Canadian). W ater
demands and wastewater flows are expected to be reduced by approximately 40% with this project (Canada Mortgage
and Housing Corporation, 2009).
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