As California continues an epic regulatory effort to reallocate water supplies for salmon habitat, an equally big question looms over the process: How much water do salmon and other native fish really need? The question is at the core of a process led by the State Water Resources Control Board to take water from existing human uses – both agriculture and urban – and rededicate it to instream environmental flows in the San Joaquin River, the state’s second-largest river.

The Bay Area imports most of its water and relies on the Sacramento-San Joaquin River Delta and its tributaries for about 70 percent of its supply. Those supplies face an uncertain future as a changing climate shrinks the Sierra snowpack and raises sea levels, and a declining ecosystem results in further restrictions — all while the Bay Area’s population and economy continue to grow. The stark reality is that 25 million people and 3 million acres of farmland are at risk of losing up to 20 percent of their future water supplies if the status quo continues in the delta.

California’s biggest water project in decades appears to be in limbo after a key irrigation district voted not to help underwrite Gov. Jerry Brown’s plan to build two giant tunnels that would re-engineer water transport in the state. The no-vote at the Fresno-based Westlands Water District — the largest agricultural water supplier in the U.S. — puts the $17 billion project’s funding on shaky ground. Will other water districts pick up the slack? Other large water agencies considering participating in the project are set to vote soon. Another key player, Los Angeles’ Metropolitan Water District, will vote on October 10.

One under-reported detail in the wake of the Westlands Water District’s vote against the Delta tunnels is the fact that this isn’t the first time the water district has supposedly rejected the project — or at least, the process. “We’re not going to spend another dime on this,” Westlands board President Jean Sagouspe told the Fresno Bee in — wait for it — 2010. That’s right. Almost seven years ago Westlands declared that it was pulling out of what was then known as the Bay Delta Conservation Plan. Its concerns at the time were essentially the same as today: That the project — which was then sized to deliver up to 15,000 cubic feet per second of water, 40 percent larger than today — would simply not deliver enough water to make it worth the cost.