“Our goal was to improve estuarine habitat by increasing net flows through the Cache Slough Complex to enhance downstream transport of lower trophic-level resources, an important driver for fish such as the endangered Delta Smelt,” write the authors—including esteemed (and recently retired) California Department of Water Resources lead scientist Ted Sommer—in the latest issue of San Francisco Estuary and Watershed Science. The pulse occurred over three weeks in July, a time when flows in the region above Cache Slough are often negative (meaning they go “upstream”) due to agricultural diversions and low freshwater inflow. Producing the pulse, which increased downstream flows from about negative-two cubic meters per second to a peak of 15 cubic meters per second in the Toe Drain of the Yolo Bypass, required releasing water from upstream reservoirs and pumping from downstream diversions in the Sacramento River.

 

“It was a lot of heavy lifting in a short amount of time, but an amazing collaborative effort,” says lead author Jared Frantzich, a senior environmental scientist with DWR, which led the effort in partnership with a host of other agencies, irrigation and reclamation districts, and private landowners. Subsequent managed flow pulses in 2018 and 2019 provided additional data and helped refine the practice, which Frantzich notes has since been included in some key Delta regulatory documents and may be used more in the future to help benefit food web and habitat conditions during summer or fall months.