Press release from the State Water Resources Control Board:
[Friday], the State Water Resources Control Board released a Draft Scientific Basis Report Supplement that analyzes the science underpinning a proposed voluntary agreement for the Tuolumne River, a tributary of the Lower San Joaquin River.
The board will hold a public workshop on Wednesday, Nov. 5, 2025, to receive oral comments on the draft report, and written comments are due by Friday, Nov. 7, 2025. A quorum of board members may be present at the workshop, but no action will be taken.
The draft report is an initial step in the process to consider amendments to the Water Quality Control Plan for the San Francisco Bay/Sacramento-San Joaquin Delta (Bay-Delta Plan) to possibly incorporate the proposed agreement. The draft was developed jointly by staff from the board, California Department of Water Resources and California Department of Fish and Wildlife.
The draft report documents the science related to the proposal, which was submitted to the board in 2022 by the San Francisco Public Utilities Commission, Modesto Irrigation District and Turlock Irrigation District. The agreement proposes flow and non-flow habitat commitments to improve conditions for native fish in lieu of flow requirements that were included in the Bay-Delta Plan in 2018.
The draft analyzes the potential changes in hydrology, water temperatures and habitat availability in the Tuolumne River and Lower San Joaquin River under the proposal. The board will use this information to assist in its evaluation of whether to update the Bay-Delta Plan to allow for the agreement.
Following receipt of public comments, the draft will be revised as appropriate and submitted for scientific peer review pursuant to the requirements of California Public Health and Safety Code.
BACKGROUND
The State Water Board is actively engaged in urgent efforts in the San Francisco Bay/Sacramento-San Joaquin Delta Estuary (Bay-Delta) watershed to address prolonged and precipitous declines of native aquatic species and their ecosystem. The Bay-Delta Plan identifies beneficial uses of water, water quality objectives and an implementation program to protect the Bay-Delta watershed and its many beneficial uses. In December 2018, the board updated the Lower San Joaquin River flow and southern Delta salinity components and is currently developing a regulation to implement these updates.
