UC DAVIS: How California’s state and federal water projects can better protect fish

Report reviews Central Valley Project and State Water Project operations for endangered fish

By Kat Kerlin, UC Davis

At least two thirds of California’s population and more than 4 million acres of California farmland rely on water delivered by the federal Central Valley Project and the State Water Project, two of the largest multipurpose water management projects in the world.

A report released this week by the National Academies of Sciences, Engineering, and Medicine reviews these projects’ monitoring, modeling, and other scientific activities — specifically actions designed to help protect endangered fish.

UC Davis Professor Jay Lund, a founding director of the Center for Watershed Sciences, and Associate Professor Steven Sadro were part of the 18-member committee authoring the report. The committee, chaired by Peter Goodwin of the University of Maryland, was established at the request of the U.S. Bureau of Reclamation to conduct a biennial review of the scientific activities of the CVP and SWP.

This first report examines three actions designed to help protect fish and offers recommendations to strengthen those actions:

1. The Shasta Coldwater Pool management action. When Shasta Reservoir was built in the 1930s, it blocked salmon from their native spawning grounds. Now, all salmon spawning, holding and rearing occurs below Keswick Dam. The coldwater pool management action has been used to help keep cold water in Shasta Reservoir until the summer and provide additional temperature control for the fish. The authors suggest a three-pronged approach to strengthen this action: 1) Continue to improve temperature management downstream of Keswick Dam, 2) continue hatcheries management, and 3) reintroduce winter-run Chinook salmon above Shasta Dam.
2. The Old and Middle River Corridor flow management action. This action aims to maximize water exports while minimizing harm to fish from pumping, particularly when the fish are rearing in and migrating through the Delta. The authors recommend more scientific transparency around thresholds for fish salvaged at the pumps and corresponding water exports. The report suggests that modeling efforts expand and build on the U.S. Bureau of Reclamation’s zone of influence analysis to better understand how temperature, aquatic plants, salinity and other water quality conditions across the Delta under various flow conditions and pumping rates impact fish.
3. Summer-Fall Habitat Action for Delta smelt. Although Delta smelt were once one of the most abundant fish in the Delta, they have now nearly vanished from the region. This action is designed to address their decline by providing more low-salinity habitat in the Suisun Marsh area. To strengthen this strategy, the authors recommend managing the location of the low-salinity zone in the fall, adjusting salinity in Suisun Marsh, and possibly releasing an additional 100,000 acre-feet of water.

The report concludes that maintaining and finetuning these actions is necessary to achieve the water projects’ goals. It adds: “Taken in isolation, the individual actions will be insufficient to achieve species recovery; rather, ecosystem-wide thinking on the part of action agencies will be imperative.”