*>EPA
United States
Environmental
Protection Agency
epa.gov/research
Water Network Tool for Resilience |
An open-source Python package for modeling disturbances to water distribution systems
Innovative Science for a Sustainable Future
WATER INFRASTRUCTURE RE,
Background
Drinking water utilities face multiple challenges,
including aging infrastructure, water quality concerns,
uncertainty in supply and demand, natural disasters, and
intentional attacks. All of these have the potential to
disrupt a large portion of a water distribution system for
extended periods of time. Increasing resilience to these
types of hazards is essential to improving water system
security. The Water Network Tool for Resilience
(WNTR) is a simulation and analysis tool that can help
water utilities predict how their system will respond to
expected, and unexpected, incidents and help inform
decisions to make water distribution systems more
resilient overtime (Klise et al., 2023). It was developed
by the United States Environmental Protection Agency
and Sandia National Laboratories.
Software Capabilities
WNTR is an open-source Python package designed to
simulate and analyze resilience of water distribution
systems. It builds site-specific resilience analysis
for water utilities, quantifies the economic and social
impact of disruptions, and helps prioritize response
action plans by integrating these critical aspects into a
single framework.
The software includes capabilities to:
• Create and modify water network models
• Simulate hydraulics and water quality
• Analyze results and generate graphics
• Assign fragility and survival curves to network
model components
• Model disruptive events such as power outages,
earthquakes, and contamination incidents
• Model response and repair strategies
• Evaluate resilience using a wide range of metrics
• Integrate dependency with other critical
infrastructure and supply chains
• Integrate socioeconomic geospatial data
• Export results into geograpic information system
(GIS) formats
4CE EVALUATION USING WNTR
Using WNTR for Decision-making
WNTR provides a flexible platform for modeling a wide
range of disruptive incidents and repair strategies that
drinking water utilities might be interested in examining.
WNTR can be used to estimate infrastructure damage,
evaluate preparedness strategies and identify worst case
scenarios and best practices for maintenance and
operations. WNTR analysis can help authorities
prioritize responses to disruptive events based on which
actions are found to have the greatest impact in restoring
access to water for the most users. A variety of resilience
metrics are available in WNTR. Commonly used metrics
include population impacted and water service
availability (WSA), which is the fraction of expected
water volume customers receive.
Usage Statistics
• Over 200,000 downloads
• Cited in 180+publications
• Users include universities, national laboratories,
engineering consultants, and water utilities
Case Study Applications
Earthquakes can cause damage to pipes, tanks, pumps,
and other infrastructure as well as power outages and
fires. WNTR includes methods to add leaks to pipes and
tanks, shut off power to pumps, and change demands for
fire conditions. When simulating the effects of an
earthquake, fragility curves are commonly used to define
the probability that a component is damaged with respect
to peak ground acceleration, peak ground velocity, or
repair rate. The tool can be used to compute peak ground
acceleration, peak ground velocity, and repair rate based
on the earthquake location and magnitude.
An earthquake case study, using WNTR, demonstrated
that infrastructure damage was associated with network
integrity and earthquake magnitude, as well as the
September 2023 c onne ct with us Online EPA/600/S-23/240
H ^ £
-------
*>EPA
resources and repair strategies used to resume delivery
of water to the community (Klise et al.. 2017). Figure 1
shows the potentially damaged infrastructure
components from an earthquake. This information could
be used to priortize which pipes could be replaced with
more earthquake resistant pipes.
/
.»* ' *
r .. ... • •
. ' -»; i
: .
• , :-y•
>¦'' J
\ • • £•. ,
V I P '
• ¦"/
a kk
> I PHW
\ \r
\
Figure 1. Water network model showing damaged pipes (red lines)
and tanks (blue circles) for a 6.5 magnitude earthquake at the
epicenter location (yellow star) [taken from Klise etal., 2017],
Figure 2 shows the predicted change in WSA over time
as repairs are implemented for the earthquake case study.
outages and infrastructure damage. WNTR was used to
evaluate the resilience of the water systems of St. Croix
and the combined system of St. Thomas/St. John to four-
week power outages in different regions of the islands
(Klise et al... 2022). The analysis quantified differences
in the water delivery, quality, and quantity during and
after the dismption. Figure 3 shows the water network
model for St. Thomas/St. John and two of the resilience
metric results for the system-wide outage scenario. WSA
was able to return to baseline soon after the outage
ended, while the tank in the West region required more
than 30 days to return to baseline capacity. The analysis
highlighted the reliance on power for water service in
different regions of the island. These results could help
provide justification for resilience planning and
preparedness to future storms.
1 Eoums&QjiW
Minimum WSA! 0.54 (1.00
-------
*>EPA
river. WNTR was used to assess the effect of source
water loss on water service availability (Chu-Ketterer et
al., 2023a). The results illustrated that conservation
efforts extended water service for an additional 20 hours
(Figure 4).
150 200 250
Time (hours)
Normal Operations
SWLC1
SWLC2
SWLC3
Time (hours)
Figure 2. WSA and pressure over Time for the loss of source water
scenarios. SWLC1 is the loss of source water scenario with zero
conservation efforts. SWLC2 is the loss of source water scenario with
conservation efforts of 25% water reduction. SWLC3 is the loss of
source water scenario with conservation efforts of 40% water
reduction and stopped service to the three highest consumers
[modified from Chu-Ketterer et al., 2023a],
Fires can cause damage to system components and/or
increase water usage at specific locations due to fighting
fires. WNTR simulates firefighting conditions by
specifying the demand, time, and duration of
firefighting. Figure 5 shows the population impacted
with pressures below 20 psi by increased demands from
firefighting at specific locations in the Poughkeepsie
network model. More details of this case study can be
found in Chu-Ketterer et al. (2023a).
500 1000
Population Impacted by Pressure Below 20 psi
¥
T > 6 ' -
hjm
. ¦ "Sr-
*• " .
r
Figure 3. Poughkeepsie water network model with nodes
highlighted with population impacted by reduction in water
pressure due to increased demands from firefighting
[modified from Chu-Ketterer et al., 2023a],
Environmental justice conems can be incorporated
within the WNTR analysis to identify additional
vulnerable areas and ensure equitable resilience within
the water distribution system .WNTR can be used to
prioritize pipes based on user-specified criteria. In a
Pennsylvania water system, a pipe criticality analysis
was combined with socioeconomic and environmental
census tract data to show how weighting based on
factors like blood lead levels, women and children
counts, historical pipe breaks, and income changes the
priority areas compared to weighting all factors equally
(Chu-Ketterer et al., 2023b). Figure 6 shows more areas
in the water network model are prioritized areas when
using the proportional weight approach.
Other disasters like floods, droughts, tornadoes,
extreme winter storms, and wind events can also
cause damage to drinking water systems. WNTR can be
used to simulate effects of these disasters like power
outages and pipe breaks.
September 2023
D
Connect with us Online
f@) ¥ •*
EPA/600/S-23/240
-------
*>EPA
Figure 4. Pennsylvania water network model showing priority areas
based on socioeconomic and environmental factors for equal and
proportional weight approaches [modified from Chu-Ketterer et a I.,
2023b],
Resilience analysis can be used to compare emergency
response actions before any disruptions, which helps
minimize water service interruptions and prevent
unintended consequences. These case studies highlight
how WNTR helps water utilities quantify the resilience
of their systems, by enabling them to:
• Evaluate the effects of disruptions on water pressure
and water service availability over time
• Test and assess response and mitigation strategies to
help restore service
• Inform capital and operational investments such as
additional storage, backup power supply/generator,
backup repair supplies, and additional repair crews
• Assist in training exercises for emergencies
K. Klise, R. Moglen, J. Hogge, D. Eisenberg, T. Haxton (2022)
"Resilience analysis of potable water service after power outages in
the U.S. Virgin Islands" Journal of Water Resources Planning and
Management 148(12).
K.A. Klise, M. Bynum, D. Moriarty, R. Murray (2017) "A software
framework for assessing the resilience of drinking water systems to
disasters with an example earthquake case study "Environmental
Modelling and Software 95.
K.A. Klise, D.B. Hart, M. Bynum, J. Hogge, R. Murray, J. Burkhardt,
T. Haxton (2023). Water Network Tool for Resilience (WNTR) User
Manual: Version 1.0, U.S. Environmental Protection Agency
Technical Report, EPA/600/R-23/098.
L-.T. Chu-Ketterer, W. Platten III, S. Bolenbaugh, T. Haxton (2023b)
"Resilience analysis and emergency response evaluation for drinking
water systems" Journal ofAWWA June 2023.
Download and Installation Information
WNTR can be installed through the United States
Environmental Protection Agency GitHub site at
https://github.com/lJS EPA/WNTR. Documentation is
available at https://usepa.github.io/WNTR/.
DISCLAIMER
This document has been reviewed in accordance with
U.S. Environmental Protection Agency, Office of
Research and Development, and approved for
publication.
CONTACT
Dr. Terra Haxton
Office of Research & Development
513-569-7810, haxton.terra@epa.gov
www.epa.gov/ord
REFERENCES
L-.T. Chu-Ketterer, R. Murray, P. Hassett, J. Kogan, K. Klise, T.
Haxton (2023a) "Performance and resilience analysis of a New York
drinking water system to localized and system-wide emergencies"
Journal of Water Resources Planning and Management 149(1).
September2023 Connect with us Online EPA/600/S-23/240
K3 10) v::? ••
------- |