Central Valley water districts subject to a state plan that diverts flows from the San Joaquin River tributaries downstream for fish are working to achieve a more holistic approach for the fishery through voluntary agreements, while also challenging the state’s flows-only approach in court. Central to the issue is a plan adopted in 2018 by the California State Water Resources Control Board that requires affected water users to leave unimpaired flows of 30% to 50% in three San Joaquin tributaries—the Stanislaus, Tuolumne and Merced rivers. The work is the first phase of the state’s water quality control plan update for the San Francisco Bay/Sacramento–San Joaquin Delta, known as the Bay-Delta plan.