“The Santa Maria River watershed is one of the four largest river systems within the northern range of the federally endangered Southern California Steelhead Distinct Population Segment (DPS). The Santa Maria River watershed supports a self-sustaining population of rainbow trout (the resident life-history form of O mykiss) in the Sisquoc River watershed. It also supports anadromous spawning of adult steelhead (the ocean-going life-history form of O. mykiss) during some wet years. Nearly the entire Santa Maria River watershed, including the Cuyama and Sisquoc rivers, are designated critical habitat for the Southern California Steelhead DPS. (Stillwater Sciences 2012, Santa Maria River Instream Flow Study: Flow Recommendations for Steelhead Passage, p ES-2).”
In 2012, NOAA Fisheries Service released the “Southern Steelhead Recovery Plan,” concluding that increasing stream flow in the Santa Maria River watershed is a vital step in restoring steelhead in all of Southern California. Twitchell Dam on the Cuyama River, tributary to the Santa Maria River, has been identified as a major obstacle to steelhead passage as Twitchell Dam, limits the timing and quantity of flow into the Santa Maria River. This prevents Steelhead fry from reaching the Pacific, and ocean dwelling Steelhead from reaching Sisquoc spawning habitat.
The 2013 Flow Study provides a detailed plan for restoring the Steelhead population using “modified operation of Twitchell Dam to approximate pre-dam hydrologic conditions in the mainstem Santa Maria River…” Stillwater Sciences 2012, Santa Maria River Instream Flow Study: Flow Recommendations for Steelhead Passage (“Stillwater Study”).
Since the conclusion of the Flow Study no corrective action has occurred and the flow regime remains unchanged.
In 2017 SLO Coastkeeper and Los Padres Forest Watch initiated litigation seeking to improve flows for the benefit of Steelhead Trout under State code 5937 and the Endangered Species Act.