As negotiations continue, representatives of Sacramento Valley water agencies say they’re hopeful voluntary agreements will serve as an alternative to state-mandated “unimpaired flows” plans being drafted by the State Water Resources Control Board. A proposal affecting Sacramento Valley tributaries would be the second phase of the water board’s Bay-Delta Water Quality Control Plan. The board adopted the first phase of the plan late last year, requiring water users in San Joaquin River tributaries to leave 30% to 50% of unimpaired flows in the Stanislaus, Tuolumne and Merced rivers to help fish populations, unless voluntary agreements on the three tributaries can be reached and adopted instead.