United States
                       Environmental Protection
                       Agency
                                     Office Of Water
                                     (4503F)
EPA841-F-94-006
August 1994
Number 13
xvEPA   TMDL   Case  Study
                       Truckee  River,   Nevada
    Key Feature:
    Project Name:
    Location:

    Scope/Size:
    Land Type:
    Type of Activity:
    Pollutants:

    TMDL Development:
    Data Sources:
    Data Mechanisms:
    Monitoring Plan:
    Control Measures:
 TMDLs protecting instream
 beneficial uses and the quality of a
 downstream lake

 Truckee River
 EPA Region IX/East-central
 California, Western Nevada
 River, watershed 2,300 mi2
 Ecoregion 5 (high mountains) and
 Ecoregion 13 (plains with low to
 high mountains) (USEPA, 1989)
 Agriculture, urban
 Nitrogen, phosphorus, total
 dissolved solids
 PS, NFS   -
 State, Truckee Meadows
 Wastewater Reclamation Facility,
 Desert Research Institute, cities of
 Reno and Sparks
 DSSAMIII
 Yes
 Riparian corridor protection,
 irrigation modification, stormwater
permitting, public education,
agricultural BMPs, wetlands
treatment systems
                                                   FIGURE 1. Location of Truckee River & Pyramid Lake
   Summary: The Truckee River flows from Lake Tahoe, California, into Nevada's Northern Basin, terminating at Pyramid
   Lake (Figure 1). In recent years, heavy growths of aquatic weeds and benthic algae, caused by high nutrient loads and low
   flows, have plagued the river. Plant respiration and decaying biomass have decreased dissolved oxygen (DO) levels in the
   river.  The low levels of DO have, in turn, impaired the river's ability to support populations of Lahontan cutthroat trout, a
   threatened species, and cui-ui (kwee-wee), a national endangered species.

   In response to these problems, the Nevada Division of Environmental Protection (NDEP) developed the Truckee River
   Strategy, a plan to coordinate the activities of agencies involved in restoring the quality of the Truckee River and Pyramid
   Lake.  The strategy includes  timetables for numerous nonpoint source control projects, such as stormwater permitting,
   wetlands treatment systems, pasture improvements, riparian restoration, and landowner education. Also, as part of the
   strategy, NDEP used DSSAM III, a water quality model, to develop nitrogen, phosphorus^and total dissolved solids
   TMDLs for the Truckee at Lbckwood, Nevada. The model is designed for systems like the Truckee, in which benthic
   processes play a major role in determining water quality. The TMDLs include load allocations for nonpoint and
   background sources and one wasteload allocation for the major point source discharger in the basin, the Truckee Meadows
   Wastewater Reclamation Facility. EPA Region IX approved the Truckee River TMDLs in March, 1994.
               Contact: Adele Basham • Nevada Division of Environmental'Protection-- Capitol
                \; ,  --333 West Nye Lane • Carson City, NV 89710 • (702} 687-4670, e>'''"'

-------
              xLakeTahoei
              \\S\SN\VSVSXV\S
                               FIGURE 2. The Truckee River-Pyramid Lake region
BACKGROUND

The Resource

The Truckee River originates on the California side of
Lake Tahoe and flows northeastward for more than 70
miles before terminating at Pyramid Lake in Nevada
(Figure 2). The Truckee basin is a closed hydrologic
system; all of its water is lost to evaporation, irrigation,
or infiltration.

Approximately 200,000 people live in the Truckee basin,
which includes the urban areas of Reno and Sparks and
several smaller agricultural communities.  The major
crops are alfalfa, cantaloupe, onions, and garlic.

The Nevada Division of Environmental Protection
(NDEP) has designated beneficial uses for the Truckee
from the state line to Pyramid Lake. These uses include
irrigation, livestock watering, water contact recreation,
non-water contact recreation, industrial supply, municipal
or domestic supply, wildlife propagation, and propagation
of aquatic life.

A drought in the Truckee basin since  1987 has caused
extended periods of low flow. High nitrogen and
phosphorus loads, combined with .the lack of a major
flushing event, have caused aquatic plants to proliferate,
resulting in abundant accumulations of benthic plants and
detritus;.
                            *
Water flow in the Truckee River is highly regulated, and
the demand for water often exceeds the supply. Since
1915, the majority of river flow during non-runoff
periods has been withdrawn from the river at Derby Dam
and conveyed down the Truckee Canal to irrigate
farmland in Fernley and Fallon, located in the Carson
River basin. Regulated flows during non-runoff periods
in the river section between Reno and the Derby Dam
are typically about 350 cubic feet per  second (cfs).
About 35 cfs remains in the river below Derby (Brock et
al., 1992).

-------
 Dissolved solids and nutrient loads enter the Truckee
 River from numerous sources, including agricultural land
 drainage, urban runoff, groundwater discharge, and
 treated wastewater effluent.  The Truckee Meadows
 Wastewater Reclamation Facility (TMWRF), located in
 Reno, is the major point source in the basin, discharging,
 on average, 28 million gallons per day (mgd) into  the
 river. The facility was upgraded to provide tertiary
 treatment in the late  1980s.  Other, less significant point
 sources  include a plastics manufacturer,- an aquaculture
 operation, water treatment plants (clarifier drainage,
 screen wash water, excess  intake water), stormwater
 outfalls, and cooling  water returns.

 Programmatic  Issues

 Water quantity and quality play  a major role in the
 management of the Truckee River.  Drought conditions
 magnify the effects of pollutant loadings from point
 sources, stormwater, and irrigation return flows.
 Jurisdictional issues, such as  water rights and inter-basin
 water transfer, affect  the preservation of wetlands, the
 protection of endangered species, and have required the
 involvement of federal, state, and local agencies (see
 box).                           *

 In 1989, NDEP developed the first version of the
 Truckee  River Strategy to coordinate multi-agency
 management activities and serve as a framework for
 progress evaluation.  The strategy summarizes measures
 for managing  point and nonpoint source nutrient loads,
 and presents a schedule for implementing these measures.
 The goals of the strategy are as follows:

    To restore the quality of the Truckee so that water
    quality standards  are attained and beneficial uses are
    supported.

    To preserve, protect, and enhance the water quality
    of Pyramid Lake.

Currently, the  Truckee River does not support its
designated uses.  As a result, the river at Lockwood is
listed  on  Nevada's 303(d) list for total nitrogen (TN),
total phosphorus  (TP), and total dissolved solids (TDS).
                Agencies Involved in
       Truckee River Water Quality Programs

   Pyramid Lake Paiute  Tribe
   Washoe County, Nevada
   Nevada Division of Environmental Protection
   U.S. EPA
   U.S. Geological Survey
   U.S. Army Corps of Engineers
  ASSESSING AND CHARACTERIZING
  THE  PROBLEM

  Water quality monitoring on the Truckee is carried out
  primarily by two entities. The TMWRF is required to
  monitor the river to demonstrate pre- versus post-
  wastewater treatment project conditions.  The Desert
  Research Institute (DRI) monitors the river monthly as
  part of Nevada's routine monitoring network (NDEP
  1993a).

  Monitoring data from the past decade have indicated that
  high nitrogen and phosphorus loads, associated largely
  with TMWRF and irrigation return flows, have
  significantly impacted the Truckee.  Figures 3 and 4
  present annual average total nitrogen and total
  phosphorus loads for the Truckee at Lockwood, Nevada.

  These elevated nutrient loads have encouraged the
  proliferation of aquatic plants and benthic algae.
  Respiration by these plants and the decay of their
  associated detritus decreases dissolved oxygen (DO) in
  the water column, resulting in violations of the DO
  standard.  Violations of the instream DO standard have
  continued in spite of recent nutrient removal
 enhancements to the TMWRF.

 Routine monitoring data collected by NDEP and the DRI
 indicate that DO concentrations regularly fall below the
 5.0 mg/L standard, especially at locations downstream
 from the Derby Dam,  such as Lockwood (Figure 5).
 Low DO has caused several fish kills, impacting
 populations of Lahontan cutthroat trout and cui-ui (kwee-
 wee) (Adele Basham, NDEP, personal communication,
 1994).  The cui-ui, a fish that has historically been a
 staple in the diet of the local Pyramid Lake Paiute Tribe,
 is on the national endangered species list.  The Lahontan
 cutthroat trout, which supports a small recreational
 fishery, is classified as a threatened species.
 DEVELOPING THE TMDLs

 Modeling

 As part of the Truckee River Strategy, NDEP, in
 cooperation with Washoe County, developed a tool to
 assess the impacts of future land use and flow scenarios
 on Truckee River water quality.  In 1987, using the U.S.
 Geological Survey's Truckee River Water Quality Model
 (Nbwlin, 1987) as a foundation, NDEP developed the
 Dynamic Stream Simulation and Assessment Model
 (DSSAM) to evaluate the potential effects of upgrading
 the TMWRF to advanced wastewater treatment.

DSSAM is designed for use on free-flowing waters
where benthic processes are important factors in overall

-------
tn
.0
g
PS
r—4
n
MOO
8000
7000
6000
5000
4000
3000
2QOO
1000
                                                                   IITotal NPS/Background
                                                                          'MDL
             1983       1984
                          -H	M
                              1985       1986
1987
Year
11988       1989       1990       1991
           FIGURE 3. Annual average total nitrogen loads in the Truckee River from 1983 to 1991
             1983
                                                                        ITruckee Meadows
                                                                        ]Total NPS/Background
                                                                        -TMDL
                                                                                                  1991
          FIGURE 4. Annual average total phosphorus loads in the Truckee River from 1983 to 1991

-------
                                          :enu  cf :'i36'Dissolved Oxygen  Is
                                           Below Standard of 5:0 ng/L
                                 o;
                                 s
                                QJ
                                tj
                                s_
                                OJ
      1832
    1431  -
  1Q31     Nitrogen Load
           at Lockwood
                                        oorastreaa
      FIGURE 5.  Impact of nitrogen load on Truckee River dissolved oxygen at Lockwood, June - August 1988
 water quality.  Key processes simulated by the model
 include transformations of various forms of nitrogen and
 phosphorus, decay of oxygen-demanding substances, and
 the carbonate equilibrium process that determines pH.
 Although the model is dynamic with respect to biological
 processes and boundary chemistry, it is steady-state with
 respect to flow. DSSAM was applied to the Truckee as
 a steady-state model; that is, river and tributary flows
 were assumed to be constant during the individual time
 periods of the model (Brock et. al., 1992).

 Because the river's beneficial uses were not being
 supported under existing standards, NDEP initiated a
 study of the Truckee in 1990 to develop more stringent
 water quality-based standards to ensure support of
 designated uses. Although new, more stringent standards
 were the original goal of the modeling project, NDEP
 decided to use permit limitations and TMDLs in the short
 term to facilitate the pursuit of other means of increasing
 DO, such as flow augmentation.

 NDEP calibrated the DSSAM model based on monitoring
 data from 1989, the first full year of data after advanced
 treatment was installed at the TMWRF. The calibration
 parameters included nutrient concentrations, flow, DO,
 pH, and various parameters associated with benthic algae
 productivity  (e.g., nutrient uptake by benthic algae, scour
 at high velocities, removal of algae by invertebrates).
The calibration  data came from the routine monitoring    .
programs conducted by the DRI, NDEP, and the cities of
Reno and Sparks.  Although the model was not formally
 validated, the modelers noted that previous applications
 of the model had shown that it behaved well.

 Once calibrated, DSSAM was used to simulate water
 quality in the Truckee under various flow and nutrient
 loading scenarios. Both agricultural and municipal
-sources were considered.  Based on the model results,
- NDEP  evaluated the ability of existing state standards to
 protect beneficial uses.  The outcome of this evaluation
 was used to determine TMDL endpoints that would result
 in attainment of standards (Table  1).
 Total Nitrogen

 Using DSSAM, NDEP determined that nitrogen is the
 limiting nutrient for plant growth in the river. The
 DSSAM model showed that, if the existing flow regime
 persisted, further restrictions on nitrogen loads would be
 needed to improve oxygen conditions in  the Truckee.

 The mean 30-day low flow at Lockwood was 273 cfs for
 the period from 1973 to 1989.  DSSAM  simulations
 determined that nitrogen loads  in excess  of 1000 Ib/day
 during low flow at Lockwood result in accumulations of
 aquatic plants and subsequent DO depletion.  Based on
 these results, Brock et al. (1992) recommended that the
low flow nutrient limit of 1000 Ib/day be maintained for
all flow regimes until further studies document the effect
of this loading on Pyramid Lake.

-------
TABLE 1. TMDLs for the Truckee River at Lockwood (NDEP, 1993b)
Parameter
Total dissolved
solids
Total nitrogen
Total phosphorus
Total Maximum
Daily Load
(Ib/day)
900,528
1000
214
Wasteload Allocation1
(Ib/day)
If flow <= 30 MGD:
If flow 30-40 MGD:
Permit maximum:
90,126
flow x 360 mg/L x 8.3
120,168
500
134
Load
Allocation
(Ib/day)
<780,360
500
80
 ! Used in the Truckee Meadows NPDES Permit.
NDEP has established the 1000 Ib/day recommendation
as the total nitrogen TMDL for the Truckee at
Lockwood. Existing state data show that the average
nonpoint source nitrogen load to the river at Lockwood is
approximately 500 Ib/day.  Consequently, a load
allocation for nonpoint and background sources was set
to 500 Ib/day. For the period from 1983 to 1991, the
mean total nitrogen load from the TMWRF was 2,489
Ib/day.  The new TMWRF wasteload allocation of 500
Ib/day requires reducing the load by  1,989 Ib/day. For
the same period, the mean total phosphorus load was  89
Ib/day, which is less than the wasteload allocation of
134.

Figure 3 shows total nitrogen  loading to the Truckee
from 1983 through 1991. Although the 1990-91 loads
are near the TMDL, they were recorded during a drought
period. Given normal rainfall, and the subsequent
normal flow, loads would have been in excess of the
TMDL.  To incorporate a margin of safety, NDEP
modelers used conservative estimates on the DSSAM
model parameters.

Total Dissolved Solids

Although the Truckee at Lockwood is identified on
Nevada's 303(d) list for total dissolved solids (TDS),  the
water quality standards  for TDS are being attained. The
TDS TMDL is proposed in accordance with EPA's
TMDL guidance, which recommends taking a proactive,
pollution prevention approach to water quality
management (USEPA,  1991).

The TDS TMDL was calculated as 900,528 Ib/day based
on simple dilution calculations using average  flow and
the state TDS standard  of 210 mg/L. The wasteload
allocation for the TMWRF varies depending on the total
discharge from the facility (Table 1). Because
conservative pollutants  are assumed not to decay or
settle, the calculated values are believed to give a
reasonable upper bound for expected instream
concentrations, thereby incorporating a margin of safety.

Total Phosphorus

Since phosphorus was also assumed to behave conser-
vatively, NDEP used the same dilution calculations that
were used for TDS to determine the phosphorus TMDL.
The instream standard for total phosphorus is 0.05 mg/L
and the TMDL was calculated as 214 Ib/day at
Lockwood. Existing data indicate that approximately 80
Ib/day ;are attributable to nonpoint sources and
background. The remaining 134 Ib/day were set as the
total phosphorus wasteload allocation for the TMWRF.
IMPLEMENTING CONTROLS

In September 1993, NDEP completed the final TMDLs
for total nitrogen, total phosphorus, and total dissolved
solids. The TMDLs were approved by EPA Region IX
in March 1994 (David Smith, USEPA Region IX,
personal communication, 1994).

The Tmckee River TMDLs provide quantitative, goals for
the various programs being undertaken to improve
Truckee water quality. Table 2 summarizes the current
and planned "water quality attainment" programs for the
Truckee basin.
FOLLOW-UP MONITORING

NDEP! and the TMWRF are responsible for follow-up
monitoring activities. NDEP will continue its long-term
monitoring of the Truckee, collecting data on total
phosphorus, total nitrogen, nitrate-N nitrite-N, un-ionized
ammonia, DO, and flow.  The TMWRF will conduct
detailed grab sample monitoring for a suite of chemical
constituents, plankton, and benthic invertebrates.  The

-------
TABLE 2. Current and proposed water quality attainment programs in the Truckee River basin
             (NDEP, 1993; Adele Basham, NDEP, personal communication, 1994)
Program or Action
Irrigation
modification
Clean Lakes
Stormwater
permitting
Steamboat Creek
Nonpoint Source
Pollution Control
Project
Washoe County
Water Quality
Education Program
Herman Ditch
Project
Flow augmentation
Wetlands treatment
systems
Stream protection
Description
Agricultural operations in the Truckee River basin generally surface-irrigate with fresh
water diverted from the Truckee. The tailwater runoff is often high in nitrogen,
phosphorus, and suspended sediments. NDEP has recommended using sprinkler
irrigation, which eliminates tailwater runoff and its associated loadings.
Using Clean Lakes grant funding from EPA, Nevada issued the Pyramid Lake Paiute
Tribe a grant to study the consequences of increased nutrient loading oh Pyramid
Lake.
Washoe County, the Nevada Department of Transportation, and the Cities of Reno
and Sparks were issued permits to discharge to the Truckee River from stormwater
outfalls. The permittees have legal authority to control pollutants in stormwater
discharges, prohibit illegal discharges, require compliance, and carry out inspections.
Reno and the Washoe County Department of Comprehensive Planning will assess
the feasibility of constructing alum addition facilities to remove phosphorus and
suspended sediment from urban runoff and agricultural return flows. Estimated
capital cost is nearly $5 million and estimated yearly operation costs are $1 ,368,400.
A public education program by the University of Nevada (Reno Campus) Cooperative
Extension, aimed at reducing nonpoint source pollution loads, targeted all residences
and agricultural activities within the basin.
The Herman Ditch Project will evaluate the water quality impacts of agricultural
activities, which are the primary nonpoint pollution source in the basin, and will
develop pollution prevention best management practices (BMPs) for agriculture.
Model runs have indicated that Truckee River water quality could be greatly improved
by purchasing water rights and augmenting the flow of the lower river during critical
periods.
Washoe County and the local Airport Authority are investigating the use of
constructed wetlands to reduce nutrient and sediment loads to the Truckee and its
tributaries.
Since animal wastes are a significant source of pollutant to Steamboat Creek, NDEP
is investigating the placement of 17 miles of fencing to keep grazing animals out of
the riparian corridor.

-------
facility also conducts bioassays and operates a continuous
DO sampler.  Data collected through these efforts will
indicate whether the TMDLs are successful in attaining
water quality standards in the Truckee River and
Pyramid Lake.  If needed, these data might be used to
refine the TMDLs if water quality standards within a
waterbody are not being attained.
REFERENCES

Brock, J.T., C.L. Caupp, and H.M. Runke.  1992.
Evaluation of water quality using DSSAM III under
various conditions of nutrient loadings from municipal
wastewater and agricultural sources:  Truckee River,
Nevada.  Executive summary. Bureau of Water Quality
Planning, Nevada Division of Environmental Protection,
Carson City, Nevada.

NDEP.  1993a. Truckee River strategy.  Nevada
Division of Environmental Protection, Carson City,
Nevada.

NDEP.  1993b. Truckee River final total maximum daily
loads and waste load allocations.  Nevada Division of
Environmental Protection, Carson City, Nevada.
Nowlin.'J.O.  1987.  Modeling nutrient and dissolved
oxygen transport in the Truckee River and Canal
downstream from Reno, Nevada. U.S. Geological Survey
Water Resources Investigations Report 87-4037. Carson
City, Neivada.

USEPAl  1989. Regionalization as a tool for managing
environmental resources.  EPA 600/3-89-060. U.S.
Environmental Protection Agency, Washington, DC.

USEPA.  1991. Guidance for water quality-based
decisions: The TMDL process.  EPA 440/4-91-001.  U.S.
Environmental Protection Agency, Office of Water,
Washington, DC.
  This case study was prepared by Research,Triangle,
  Institute, Research Triangle. ParkJ'NC, in conjunction
  with  USgPA;* Office  of Wetlands,  Oceans,  'and
  Watersheds, Watershed Branch.  To obtain copies,
  contact   your  "BPA.  -Regional   ~303(4)/TM£>L
  Coordinator.    "

-------