Scientific Basis Report in Support of New and Modified Requirements for Inflows from the Sacramento River and its Tributaries and Eastside Tributaries to the Delta, Delta Outflows, Cold Water Habitat, and Interior Delta Flows

The State Water Board is conducting a review and update of the 2006 Bay-Delta Plan to ensure that beneficial uses of water in the Bay-Delta watershed are reasonably protected. Phase I addresses potential changes to San Joaquin River flow requirements for the protection of fish and wildlife and potential changes to southern Delta salinity requirements for the protection of agriculture.1 Phase II addresses changes to the Bay-Delta Plan to protect native fish and wildlife in the Sacramento River, Delta, and associated tributaries.

This Scientific Basis Report (Science Report or Report) is being prepared to support the Phase II update of the Bay-Delta Plan. It describes the science on which proposed changes to the Bay-Delta Plan will be based. A working draft version of the Report was released on October 19, 2016, to receive early scientific and public input on the science related to Phase II prior to submittal of the Report for external peer review. The State Water Board received input from a number of interested parties including water users; environmental groups; and local, state, and federal agencies. In recognition of the vision for “one Delta, one science” articulated in the Delta Stewardship Council’s (DSC) Delta Plan, the State Water Board also requested that the Delta Independent Science Board (Delta ISB) conduct a review of the Report. The State Water Board appreciates the valuable comments and suggestions that have helped further strengthen the scientific content in this version of the Report.

In addition, comments related to regulatory and policy issues were raised that have further informed the development of proposed changes to the Bay-Delta Plan, including implementation approaches. The general components of these changes are summarized below and in more detail in Chapter 5 for context, and will continue to be refined as the planning process moves forward. This Report and the peer reviewers’ responses will be posted on the State Water Board web site and become part of the record for this Bay-Delta Plan update. Content from this Report will be included in a larger Staff Report that will also contain information on environmental, economic, and other analyses of potential changes to the Bay-Delta Plan, including regulatory and policy considerations of competing uses of water (including municipal, industrial, agricultural, power production, and other environmental uses of water such as wetland and wildlife refuge supplies). These issues are not addressed in this Science Report. Further, while a description of the approach for proposed changes to the Bay-Delta Plan is provided, the exact regulatory language is still under development and will be informed by the science in this Report and other information that will be included in the Staff Report. The public and agencies will continue to have opportunities to provide input throughout this process.