Matthew J. Deitch

Evaluating effects of water rights diversions in coastal California streams over spatial and temporal scales

While much of the western United States may be considered arid, some regions receive more water annually than most agricultural zones in the rest of the US. The problem inherent to agriculture in a region such as California’s north -central coast is that the timing of water availability is opposite that of need: roughly 45 inches of rain falls in the Russian River watershed, but all between November and March. Vintners (representing the most common form of agriculture in the region) therefore must meet water needs by obtaining it from supplies available during summer growing months, principally groundwater, surface streams, and artificial impoundments. Diversion of flow from small streams may conflict with flow needed by federally protected salmonids for spawning and rearing habitat. Historical stream flow data and water rights records highlight the disparity between stream flow and water needs: streams varying in size may dry at different points after the rainy season, but the demand for water from these streams continues throughout the summer. The difference between water demanded from small streams and the amount of water they can provide may be the primary hurdle to restoring coastal river fisheries.