Physics to Fish: Understanding the Factors that Create and Sustain Native Fish Habitat in the San Francisco Estuary

The Bureau of Reclamation (Reclamation) operates the Central Valley Project (CVP), one of the nation’s largest
water projects. Reclamation has an ongoing need to improve the scientific basis for adaptive management of the CVP
and, by extension, joint operations with California’s State Water Project. The U.S. Geological Survey (USGS) works
cooperatively with the Bureau of Reclamation to provide scientific support for the management of Reclamation’s
CVP project. Major habitat restoration efforts and a new water-diversion point are planned to benefit delta smelt
(Hypomesus transpacificus) and other species of concern while ensuring the reliability of water supply. In addition,
various flow actions and management activities have been identified as possible methods to increase populations of delta
smelt and salmonid (Oncorhynchus spp.) runs of concern. The overarching goal of this cooperative project was to provide
Reclamation with the scientific information needed to evaluate the efficacy of ongoing and future adaptive management
actions and to improve the scientific basis for more flexible CVP operations that would achieve water-supply reliability
and fish protection. The research and monitoring described in this report comprises the period 2015–19 and focuses on
management issues related to native fish species of concern, especially delta smelt. Conserving the delta smelt population while providing a reliable water supply is a primary management and policy issue in California.