ALEX CHADWICK, host:
First, the very rare tiny fish that's shut down the water source for 25 million people in Southern California. This is the endangered delta smelt. It has stopped the massive pumps that send water from Northern California to the thirsty south. From member station KQED, Tamara Keith reports that the fish is struggling as its ecosystem crumbles.
TAMARA KEITH: The Sacramento San Joaquin Delta is like the hub of California's incredibly complicated water supply system. And as water is drawn into the powerful pumps at the southern end of the delta, some unfortunate fish gets sucked in too. State operators capture and count some of those fish to check the impact of the pump.
Mr. CLIFF PETTYJOHN (Pump Operator): We ran tank for about an hour. We're going to see how many fish try to get out of here...
KEITH: Cliff Pettyjohn works at the pump salvaging fish. He transfers this hour's catch from a tank into a bucket.
Mr. PETTYJOHN: Looks like we got three steelheads and it looks like we might have had a silverside in there.
KEITH: State wildlife authorities used this information to calculate the take at the pumps, the number of fish presumed dead or displaced. Until late last month, Pettyjohn and other workers hadn't seen many delta smelts. It's a two-inch long endangered fish that smells like a cucumber and only lives in the delta. Then suddenly they got more than 200 in a week.
Bill Jennings, with the California Sport Fishing Protection Alliance, says the once prevalent smelt are on the precipice of extinction.
Mr. BILL JENNINGS (California Sport Fishing Protection Alliance): They've reached numbers to where we can name them rather than count them.
KEITH: He and other environmentalists blame the smelts' decline on the havoc caused by pumping so much water to supply farms and cities to the south. State officials say there are other factors - pesticides and invasive species. Regardless of the cause, Ryan Broddrick, head of the California Department of Fish and Game, says the state couldn't continue operating the pumps and risk killing more smelt.
Mr. RYAN BRODDRICK (California Department of Fish and Game): Our best information is we have a very low population. So every one of these fishes is critical.
KEITH: The immediate problem is it seems the tiny fish are hanging out right near the pumps. So until they move on, state water operators and the millions of people they supply are in a bind.
Ms. FIONA HUTTON (Water Contractors Spokeswoman): We hope obviously that the fish move away from the pumps and we will be able to resume pumping.
KEITH: Fiona Hutton is a spokeswoman for the state water contractors, all those public agencies that get water from the delta.
Ms. HUTTON: All of them do have contingency and emergency supplies that they can pull and draw from. Some of them will be relying more on ground water resources. Some of them will be able to rely more on surface storage reservoirs.
KEITH: California officials say they hope the pumps can start up again in a week or sooner. But this issue is much bigger than the tiny delta smelt. The fish is an indicator species for the entire delta ecosystem, a sort of canary in the coalmine. Lester Snow is director of the California Department of Water Resources.
Mr. LESTER SNOW (California Department of Water Resources): What we're identifying here is we have a system that's not sustainable. It's not sustainable for our water supplies and it's not sustainable for the ecosystem. So we're going to manage our way through this, this summer, but we could be right back here next year at this time.
KEITH: That's what Jeff Kightlinger is afraid of. He's general manager of the Metropolitan Water District of Southern California, which supplies drinking water from the delta to Los Angeles and a bunch of other cities. He says the dire situation of the delta needs to be treated like an emergency.
Mr. JEFFREY KIGHTLINGER (Metropolitan Water District of Southern California): Right now we're turning up the pumps. We all know it's just one of half a dozen causes impacting the fish. And other than looking at the others, there's no actions proposed and none even in the process of getting proposed.
KEITH: And in a sign of just how serious the situation has become, water exporters like Kightlinger, and environmentalists who were once diametrically opposed, are working together. They're calling on the governor and the state legislature to allocate millions of dollars for habitat restoration.
For NPR News, I'm Tamara Keith in Sacramento.