SPAWN to study Lagunitas Creek flows

07/06/2017

The Salmon Protection and Watershed Network is collaborating with a University of California, Berkeley professor on a new study focusing on how releases from Peters Dam influence floodplain areas important to endangered coho salmon and threatened steelhead trout. The dam crosses Lagunitas Creek at Kent Lake, the largest and newest reservoir within the Marin Municipal Water District. This month, the district released around eight cubic feet per second, an amount set by a 1995 State Water Resources Control Board order aimed at balancing fishery protection and water rights issues in the creek. In wetter months, the flows can reach as high as 25 cubic feet per second. But SPAWN wonders if the order could be improved upon. “We want to provide the most current information on how floodplains impact or provide for a habitat,” said Preston Brown, the group’s watershed conservation director. According to Mr. Brown, floodplains provide optimal feeding pools and protection for juvenile salmon and trout. “We are not arguing for more water,” he said. “Instead, we want to study the floodplains and the flows through the floodplains, and see what flows are needed to initiate significant juvenile salmon habitat.” The study will center around winter and spring flows over the next four years, focusing on areas between Devil’s Gulch in Samuel P. Taylor State Park and Black Mountain Ranch. The findings will lead to recommendations that SPAWN will present to Marin Municipal Water District and the state Department of Fish and Wildlife. The study is principally funded through a $158,000 grant awarded to SPAWN in May from the Wildlife Conservation Board. SPAWN is pitching in $65,000 and will collaborate with Ted Grantham, a Berkeley environmental science professor, to use topographic mapping, 2D hydraulic modeling and real-time hydrologic measurements to determine the floodplain activation flow. Mr. Grantham said a hydraulic model can help understand how flows correspond to different water surface channels and velocities within a stream channel. “As you incrementally change the volume of flow, we want to know at what point do these small floodplains become inundated and what value they might have for juvenile salmonids in this winter period,” he said. Todd Steiner, SPAWN’s executive director, said the Lagunitas Creek Technical Advisory Committee—a group composed of representatives of numerous local, state and federal agencies—reached out to the nonprofit about modifications to the flows a decade ago.