Watershed Assessment Framework - Application in the Napa River Basin
The Watershed Assessment Framework (WAF), as applied to the Napa River watershed, is a method of reporting on key indicators of watershed health over time to guide watershed management actions. Watershed health is defined broadly, to include ecological, terrestrial, aquatic, water-related, social, and economic measures. The outcomes of this application are an easily understood watershed health Report Card on the health of the Napa River watershed, and more in-depth technical report detailing the process and analysis behind the WAF application and development of the Report Card.
The Napa River is the largest river system that empties into the northern portion of San Francisco Bay. Relative to other watersheds in the North Bay, the Napa River watershed remains predominately rural. The watershed supports an abundance of wildlife and native fish species, including steelhead and Chinook salmon. Similar to the rest of the Bay-Delta region, the abundance and distribution of anadromous fish in the watershed has diminished since the 1940's.
Application of the WAF in the Napa River watershed is one means by which to track a limited number of informative indicators, allowing watershed residents and managers to assess the condition of the watershed, to see trends or changes in those conditions over time, and to adapt their management actions to achieve desired conditions (i.e., watershed goals).
The Watershed Assessment Framework (WAF) is based on an approach developed by the US EPA and others. The WAF organizes environmental information into categories corresponding to major watershed attributes and processes. Indicators selected under each category are based upon the goals and objectives for the watershed being evaluated. The WAF approach is based on metrics and indicators that are organized into a hierarchical structure corresponding to aspects of natural and human systems that are termed system "attributes".
Goals & Objectives
Central to the application of the WAF is the description of goals for the watershed or region being evaluated. From these goals, measurable objectives are developed. Indicators are chosen that allow evaluation of the objectives and thus the goals. A critical and sometimes missing component of indicator system is an explicit or transparent link between the goals for the system and the indicators chosen to represent the system's condition.
The condition scores across all 14 indicators are not extreme. Overall watershed health of the Napa River can be described as fair (many of California's watersheds are in fair or worse condition). What should be of most concern to the Napa River watershed community is that conditions are only fair and for many indicators there is a measurable decline in condition over time. The reliability of these findings varies dramatically among the 14 indicators scored. Ideally, all indicators would be independent of each other. However, none of the indicators analyzed is strictly independent, but each is different enough from the each other to reflect a useful aspect of watershed health.
Although not perfect, use of these measures (i.e., indicators) of watershed vital signs can help guide community decisions to turn declining trends around and encourage a trajectory toward a healthy and more sustainable watershed. In general, the community needs more and better data, and deeper analysis, to fully understand the health of its watershed and if the watershed is meeting established goals. A full report on the WAF project is available at the Napa County Conservation, Development & Planning Dept. and here on the Watershed Information Center & Conservancy (WICC) website.
Funding & Partners
The WAF project was funded by the California Dept. of Water Resources. The project team included, the Napa County Conservation, Development and Planning Dept., UC Davis, Dept. of Environmental Science & Policy, Napa County Resource Conservation Dist., Sonoma Ecology Center, and Oregon State Univ., Agricultural & Resource Economics Dept.