Truckee River Watershed
A Watershed Approach to Improving Water
Quality on the Truckee River
As water quality planning takes on a holistic perspective, looking at all activities within a watershed, TMDLs have become a valuable tool in translating water quality standards to a combination of point and nonpoint source controls needed to achieve instream goals.
The goal of the TMDL program is to identify impaired water bodies and allocate pollution control responsibilities amongst pol lu tion sources in a watershed. The TMDL program encourages the use of a wa ter shed ap proach to sys tem at i cal ly identify, evaluate, and pri or i tize point and nonpoint sources of pollution for additional controls.
As part of the TMDL program, the EPA is in the process of finalizing its water quality trading program. This in cludes the trading of nonpoint and point-source pollutant loads. This approach realizes that it may be more cost-effective to control nonpoint sources than to impose additional point-source controls. Therefore, there is the opportunity for point-source dischargers to save money through funding nonpoint source reduction activities while im prov ing water quality at the same time.
Carollo Engineers is currently developing a watershed program for the Truckee River Basin, including the cities of Reno, Sparks, and Washoe County, Nevada. This work includes developing models to provide the technical basis for recommendations for water quality trading for nutrients and total dissolved solids (TDS) on the Truckee River.
The State of Nevada’s Division of Environmental Protection (NDEP) initially established TMDLs for nitrogen, phosphorus, and TDS for the Nevada side of the Truckee River in 1994. The major point-source discharger to the Truckee River, the TruckeeMeadows Water Reclamation Facility (TMWRF), as a result has waste load allocations (WLAs) for total nitrogen, total phosphorus, and TDS in their NPDES discharge permit. Therefore, the Agencies have implemented a multi-year program to develop the tools (i.e., models) needed to provide the technical basis to revise the TMDL. The program involves the implementation of structural and non-structural alternatives, incorporation of a seasonal discharge and development of a phased permitting approach for water quality trading.
The most challenging aspect of the project is to develop revised TMDLs, a water quality trading frame work and agreement and associated permit language. This will require the successful development of a system of watershed and water quality models to provide the scientific and engineering basis for increased nutrient as similative capacity in the river.
Water Quality/Watershed Modeling Tools
Many natural and man-made pollutant sources must be assessed through the development of a watershed model, verifying and improving an existing water quality model, and implementing a Regional Coordinated Monitoring Program to obtain the required data. The Carollo team (including subconsultants Systech and Aqua Terra) developed a water shed model in accordance with the EPA’s Guidance for Water Quality-Based Decisions: The TMDL Process (April 1991).
The Carollo team verified and calibrated the DS-SAMt water quality model, as well as led a peer review of the model by an independent modeling consultant. In addition, the Carollo team (including Limnotech and RCR) integrated the DSSAMt algal algorithms into HSPF. The water quality models are being used to evaluate various management alternatives, including non-structural programs and a seasonal discharge, and the associated water quality impacts to the Truckee River.
The Watershed Analysis Risk Management Frame-work (WARMF) model provides an estimate of the nonpoint source loading contributions from the wa-tershed. The WARMF model is based on the EPA’s watershed approach and provides a decision support system for the region’s stakeholders with which to make management decisions regarding pollutant reduction measures. The WARMF model, using a daily time step, is driven by meteorology and land-use data, and integrates land, rivers, and reservoirs. It utilizes a "user-friendly" graphical user interface, and integrates four separate but related models.
Carollo identified a number of potential nonstruc-tural alternatives for implementation on the Truckee River with the potential to improve water quality. Alternatives include river and riparian restoration, storm water management practices, water augmen-tation, septic tank conversion, water reuse and others. Based on a review of the potential alternatives, a list of potential project scenarios including structural and nonstructural alternatives, was developed for modeling evaluation.
Based on the modeling results, stakeholders will identify potential nonpoint source trades, which will be integral to the success of the TMDL and water quality trading program. The watershed model serves as a screening/management tool to manage existing and future point and nonpoint sources of loading, and to better understand the consequences/impacts of various water quality control activities.
In order to implement a water quality trading program, a phased permitting approach has been developed. This three step process includes: inclusion of a permit reopener clause for trades as a minor permit modification; development of proposed trades and a associated provisions and monitoring requirements; and development of the final trade ratio and phase in schedule for credits.
The Trade-Offs
Through the use of WARMF, DSSAMt and HSPF modeling tools, the Carollo team is assessing various point and nonpoint sources of pollution from Lake Tahoe to Pyramid Lake. By identifying the sources, planners are able to target nonpoint source pollution control measures, prioritize areas by levels of impact, develop land-use policies consistent with the assimilative capacity of the river, and provide a basis for local governments to support developmental policy changes. Through the reduction of nonpoint sources, the region plans to apply the pollutant credits to help TMWRF comply with water quality-based effluent limits established for the Truckee River
Monitoring
The Carollo team is also managing a Coordinated Monitoring Program (CMP) to support the watershed/water quality modeling work, assist in developing a revised TMDL, assess compliance with the water quality objectives, and improve data quality.
Developing the CMP involves identifying the past and current monitoring activities in the region and evaluating the water quality model, watershed model, NPDES permit, and other agency needs.
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