Implementation Responsibility and Accountability Measures: Assign
Implementation Plan: Develop
Monitoring Plan: Develop to Track Effectiveness of Implementation Plan
Maintain SCBWMI as Stakeholder Forum
FY 02/03 Subtotal
Prepare Package for Regional Board Consideration
Prepare and Support Administrative Record and OAL Regulatory Summary
FY 03/04 Subtotal
NAPA RIVER – SEDIMENT TMDL WORKPLAN DRAFT - TASKS, TIMEFRAMES, AND RESOURCES ARE DEPENDENT ON AVAILABILITY OF RESOURCES AND STAKEHOLDER SUPPORT
Water Bodies: Napa River
The primary issues driving a sediment total maximum daily load (TMDL) in the Napa River watershed are: 1) degradation of salmonid habitat; 2) turbidity in local water supplies; and 3) increased flooding due to streambed aggradation. Resolution of water quality impairment due to sediment will require a stakeholder involvement process, interdisciplinary watershed assessment, and inter-agency cooperation to facilitate coordination of Clean Water Act and Endangered Species Act regulatory decisions.
Stakeholder involvement is needed throughout the process to educate stakeholders about the problems, communicate regulatory requirements and agency intentions, resolve disputes, and provide incentives for pro-active problem solving by local entities. This is the most important element in all watershed programs.
Interdisciplinary watershed assessment is needed to identify the mechanisms for existing and potential impacts to streams. The assessment will be used to: a) confirm or reject sediment listings; b) determine whether other causes for impairment exist (e.g., riparian impacts, flow depletion, temperature pollution, etc.); c) refine TMDL problem statement(s), d) focus subsequent technical assessments; and e) implement initial restoration and management actions. Advanced scientific methods and highly qualified practitioners are needed to foster acceptance of the results.
Many local, state and federal agencies are involved in watershed protection efforts in the Napa River Watershed. A Napa River Watershed Task Force (NRWTF) has been convened by the Napa County Board of Supervisors (beginning February, 1999). This task force is comprised of local citizens selected for their expertise and their ability to represent the views of interest groups within the Napa County community. Numerous agencies including the Board, Natural Resources Conservation Service and the Napa County Resource Conservation District are advisory to this task force. The short-term mission of this task force is to make recommendations to the County Board of Supervisors regarding interim measures specific to the development of vineyards, and intended to protect the economic, ecological and social health of the community. It is hoped that this forum will continue to serve as a long-term task force to address important issues in the Napa Valley such as the sediment TMDL.
The proposed Napa River watershed assessment is a two-phased study. The study plan has been modified to fit into the required TMDL format (problem statement, numeric targets, source, allocation etc.). The first phase will describe the current biological and geomorphic state of the Napa River system. The second phase is designed to develop an understanding of watershed processes and their links to the state of the River. Specifically, Phase 1 is a rapid assessment of current in-stream channel conditions, designed as a limiting factor analysis for steelhead and chinook, coupled with a limited review of current and historical watershed conditions. Phase 2 is a watershed analysis designed first to establish the links between geomorphic processes, in particular sediment sources, and channel conditions. Phase 2 will incorporate the development and use of an erosion control model designed to evaluate different land use scenarios. Phase 1 and 2 will employ the use of reference states (historical or pre-management) to help evaluate current conditions and trends, and potential future conditions and trends.
Sediment listing is based predominately on qualitative visual assessments of the Napa River and its tributaries by Board and CDF&G staff. The Napa River and numerous tributaries support steelhead, federally listed as a threatened species. Additionally, the California Freshwater Shrimp (Syncaris pacifica), listed as endangered by state and federal government, resides within the watershed. The beneficial uses affected include: Cold Freshwater Habitat, Warm Freshwater Habitat, Fish Spawning, Fish Migration, Preservation of Rare and Endangered Species Habitat, Wildlife Habitat, and Municipal and Domestic Water Supply.
Observations leading to the conclusion that these beneficial uses have been adversely affected are the following:
High levels of embeddedness (>50%) in potential spawning areas (detailed survey in Dry Creek, a subwatershed, and random spot observations in other subwatersheds. Thorough surveys have not been conducted throughout the watershed);
Evidence of armoring below municipal dams (potential lack of suitable sized spawning gravels);
Evidence of the in-filling of pools;
Bank failure and instability throughout the River and tributaries (due to numerous factors including local streambed aggradation);
Loss of riparian trees which provide bank stability, shade, and instream cover (frequently removed by high flow events or human activities);
Evidence of local streambed aggradation and degradation, and resulting creation of migration barriers.
The above impacts potentially affect the ability of cold water fish such as steelhead, to spawn, rear and migrate. Additionally, loss of pool habitat and riparian cover affects the Freshwater Shrimp (Syncaris pacifica).
The predominantly qualitative assessments to date are random and poorly documented. Causal linkages have not been investigated on a watershed scale. The first step in the TMDL process is to define the extent of the adverse impact throughout the watershed.
Habitat conditions in stream channels are shaped by more than sediment load. They are shaped by the interactions of streamflow, sediment, large woody debris, and stream-side vegetation. This implies that a broader, more holistic, analytical framework is needed when a principle objective of a TMDL is recovery of cold water fish habitat for species such as steelhead. Such a framework is usually referred to as watershed analysis, as has been implemented in Washington state and Federal forest lands (Washington Forest Practices Board, 1993; Federal Ecosystem Management and Assessment Team, 1993). Due to the size of the Napa River Watershed (426 mi2), and its complexity in terms of physical and biological conditions and land use history , coupled with time and budget constraints, a modified approach to watershed analysis is envisioned. The proposed approach will incorporate GIS/DTM modeling and other models (i.e., temperature) to overcome these constraints.
Other problems that have occurred in the watershed and are linked to high sediment loads include impacts to municipal water supply systems and increased flooding. Municipal water supply systems are regulated by California’s Surface Water Filtration and Disinfection Treatment Regulations (SWFDTR) which specify turbidity standards. The cities in the Napa River Watershed are dependent on local surface water supplies and the State Water Supply Project for drinking water. During periods of heavy rainfall (i.e., 1995 and 1998) surface water turbidity in many of the surface water reservoirs is too high and prevents effective treatment. Those facilities that have an alternate water source, such as the City of Napa, switch to this source. Other facilities, such as the Rector Reservoir Facility, continue to treat the highly turbid water, resulting in violations of the SWFDTR standards.
Aggradation of the River and local tributaries has contributed to localized flooding in the towns of Yountville and St. Helena. This has resulted in requests to CDF&G and the Board for dredging and stream alteration permits.
Additional Work Needed: Watershed assessments are needed to: a) confirm sediment impairment and define the extent of impacts; and b) determine whether other causes of impairment occur (flow depletion, riparian impacts, temperature etc.). Results may be used to: a) update 303(d) listing(s); b) refine TMDL problem statement; c) focus subsequent technical assessments; and d) develop and implement watershed plans with restoration and management actions.
Development of a preliminary historical reference state model including: 1) GIS/DTM model development 2) Initial historical analysis (using the existing Citizen Volunteer Water Quality Monitoring Program for collecting historical data on reference conditions);
In-stream channel and habitat assessment;
Limiting factor analysis;
Census of Fish and Other Species of Concern.
Year 1 0.25 PY $150,000 contracts
Year 2 0.25 PY; $100,000 contracts Products: 1) limiting factor assessment to confirm or reject sediment listings, and determine whether other causes for impairment exist (e.g., riparian impacts, flow depletion, nutrient pollution, etc.); 2) updated water body listing(s).
Numeric Targets: The Desired Future Condition: The desired future condition is adequate distribution of suitable spawning, rearing, and refuge habitats as necessary to support "Fish in Good Condition" at the individual, population, and species assemblage levels (Moyle et al., 1998).
Development of numeric targets may require a scientific research project at the regional level for San Francisco Bay (see Regional Indicators TMDL). The project will be designed to specify allowable sediment discharge rates needed to restore desired quality of habitat which are obtainable within given sub-basin22 and stream reach types23. For sediment, there are two types of targets needed: 1) allowable rates of sediment input to stream channels (sediment production targets); and 2) stream habitat quality. Sediment production is the focus of measurement and compliance targets because it is the direct expression of what is coming off the land. Measurement of sediment load in streams is much less useful than sediment production because: a) stream sediment load does not lead to distinction of natural versus management-related contributions; b) load will vary dramatically between years independent of management activities (see discussion below); and c) there are temporal lag times of a few-to-hundreds of years between delivery and discharge of sediment stored in channels.
Sediment production targets should be based on a ratio of anthropogenic to total sediment production measured on a 1-to-5 year basis per the following rationale:
Inter-annual variation in sediment production rates is extreme in California and governed primarily by the substantial variation in character of a given wet season. A ratio between anthropogenic and total production is superior to a measurement of total production, therefore, because anthropogenic contributions are always placed within the context of the hydrologic driving forces.
Sediment production rates can be measured at least as accurately as sediment load in streams. Costs are similar, and professional practices exist for distinguishing whether causation is natural or management related.
Measurement frequency is suggested as once in one-to-five years to aid adaptive management decisions and evaluate effectiveness of management practices and restoration projects.
In the Napa River Watershed a calibrated erosion control model will be developed to evaluate different land use scenarios and BMP effectiveness.
Numeric Indicators for Instream Habitat
Numeric indicators are needed to describe properly functioning habitat conditions for selected target species (i.e., steelhead). In-stream habitat attributes which serve as the indices of the quality of spawning, rearing, and refuge habitat are needed. These indicators must distinguish between conditions in different channel types, be easily measurable and sensitive to land use changes. These may include: pool volume, baseflow persistence, spawning gravel permeability, large woody debris loading, and overstory canopy closure. Loss of pool volume by fine sedimentation (Vstar method) and stream bed permeability at spawning sites pertain to sediment load; over-story canopy closure and large woody debris loading would pertain to riparian management.
Once the regionwide effort to establish targets is completed, sediment TMDL numeric target development in the Napa River should be reduced to adaption of the regionwide targets, development and use of a calibrated erosion control model to evaluate different land use scenarios and BMP effectiveness, and the development of rapid sediment budgets as decribed in the Source Analysis section below.