Agricultural Efficiency in the San Gregorio Watershed

Agriculture and water supply, for obvious reasons, are inextricably tied. In California this relationship is of particular concern as the state continues to face water supply challenges from population growth and a changing climate.  Pressure has increased for agriculture to use water more efficiently and to make more water available for urban and environmental uses. Numerous technologies and management approaches that conserve water while maintaining yield and production standards are being pursued throughout the state.

The American Rivers’ California Regional Office, with funding from the EPA West Coast Estuaries Initiative Grant Program, is piloting one such approach in the San Gregorio Creek Watershed.  This approach is the legal transfer of agricultural water rights from low-flow summer diversions to winter storage diversions, ensuring healthy stream flows year round. This means that those who have the right to take water out of the stream during the dry summer months will instead take that water during the wet winter months and store it for later use. By leaving water in the river in the summer months, the San Gregorio Creek watershed is able to maximize the benefits a healthy river provides.  In addition, this approach allows agricultural water diverters more security in the amount of water available to them as they divert during the high-flow winter months.

American Rivers works with multiple partners including the Natural Heritage Institute, San Gregorio Environmental Resource Center, Stillwater Sciences, and USGS. The goal of this project entitled: “San Gregorio Creek Watershed: Filling Critical Flow Needs” is to increase water quality and habitat through a non-regulatory approach to healthy river flow while maintaining agricultural productivity.

Objectives in support of this goal include:

• Transfer of agricultural water rights from low-flow summer diversions to winter storage diversions to meet healthy stream flows;
• Increase the number of agricultural acres under production by providing a secure winter-diversion water supply instead of a tentative summer diversion;
• Design a healthy flow schedule so that increased flows provide maximum water quality and habitat benefits;
• Collect baseline and performance monitoring data to quantify measurable impacts; and
• Transfer knowledge gained in implementing this innovative approach to other coastal watersheds through a robust peer outreach program.

California's unique geography and Mediterranean climate have allowed the State to become one of the most productive agricultural regions in the world. California produces over 250 different crops and leads the nation in the production of 75 commodities. Most of this production would not be possible without irrigation. In an average year, California agriculture irrigates 9.6 million acres using roughly 79% of the water diverted from surface waters or pumped from groundwater.

American Rivers hopes to further benefit California’s communities by replicating the San Gregorio Creek watershed approach along the coast and perhaps more broadly.

The San Gregorio is a coastal watershed which provides water for a rural agricultural community and for sensitive and endangered species. The watershed is unique in that public land accounts for over one-third of land ownership. With the exception of three small communities, the remaining land use is largely private, undeveloped land and range. Agriculture remains a primary activity, bolstering the regional economy and underpinning the cultural identity of the San Gregorio community. In fact, several farms are headed by third or even fourth generation farmers. Thousands of acres are under production, most of which are concentrated along the floodplains and the mainstem of the Creek.

The watershed is also home to coho salmon (Oncorhynchus kisutch), tidewater goby (Eucyclogobius newberryi), and steelhead trout (Oncorhynchus mykiss), the first two federally-listed endangered species and the latter listed as threatened. Other endangered, threatened, or species of special concern residing in the watershed include: California red-legged frog, San Francisco garter snake, marbled murrelet, southwestern pond turtle, and Pacific lamprey.