Overwhelming costs and technical complexity compound this kind of institutional apathy. Since large-scale groundwater cleanup is, by most measures, not feasible, a different approach called "pump-and-fertilize" has been proposed. In essence, farmers would use nutrient-loaded groundwater for both irrigating and fertilizing, a practice that, over time, could gradually reduce nitrate levels in aquifers. Another idea is a tax on nitrate-rich fertilizers, meant to dissuade farmers from overusing them. The tax funds would be used to tackle nitrate contamination in towns served by small community water systems. (The UC Davis report estimates it will cost $36 million annually to bring clean water to the two regions examined in the study -- either through new infrastructure or securing new sources of water.) Not surprisingly, agricultural groups are strongly opposed. "It's going to take action not only from the water board but the Legislature and other state agencies, to move forward," says John Borkovich, program manager for the state water board's groundwater monitoring program.

The most promising technical fix may, in fact, be rooted in the ties forged by the AGUA coalition itself. The hope is that these small towns can pool their resources to create larger districts with economies of a scale capable of reducing the high costs of treatment. "If you take seven communities and combine them into one district," says Solis of the Community Water Center, "you eliminate the costs of seven secretaries, seven attorneys, seven engineers, seven everything. You're also much stronger politically."

Steve Worthley, a member of the Tulare County board of supervisors, is exploring just such a possibility. The county, which took over operation of Seville's water system by court order a few years back, is considering linking it up with the water system of the nearby town of Yettem. He notes that the greatest impediments to consolidation are political. "There would have to be an election to create a district and form its boundaries and determine its governance structure. But it can be done." He adds that another nearby district is considering delivering clean water to these towns via water "swaps," which entail exchanging cleaner surface waters for groundwater stored in large underground reservoirs.

While the concept of swapping tainted groundwater for cleaner surface water seems like a no-brainer, it's not as simple as it sounds, explains Worthley -- particularly in years like this, in which, as of May 1, the state's snowpack stood at a meager 17 percent of average. Communities across the region have no choice but to turn to groundwater to augment supply.

Given the myriad threats to the Central Valley's groundwater, I ask if the state might have a larger role to play, helping the county to more carefully manage the pumping of groundwater and more rigorously regulate sources of pollution. "I'm totally opposed to it," says Worthley. "We can manage our own groundwater."

Like most places in California and across the country, already-strapped Tulare County was decimated by loss of tax revenues during the financial downturn. "We know we have a problem, and we're trying to fix it," says Worthley. "We don't have the money to fix it. The community services districts don't have the money to fix it."

So where will Tulare County get the money? I ask. "We're looking for some assistance from the state," he says.

Back in Seville, as we walk toward Becky Quintana's house and the snowcapped peaks beyond, Quintana reflects on what's been accomplished. Still, she acknowledges that the struggle to secure clean water for her community never ends.

"People always ask me, 'How come you don't just move?' Is that going to solve my problem -- just taking off? My parents built their house here 60 years ago. Should I just say, 'OK, I'm leaving, the water will take care of itself?' " She shakes her head emphatically, her large earrings swinging defiantly in the cool spring air. "It's not just about me. It's about the next generation. It's about the next human being that's going to want to come make a home here. Why not make a difference?"

Jeremy Miller is a contributing editor for High Country News. He writes from his home in Richmond, California.

This story was made possible with support from the Kenney Brothers Foundation and with reader donations to the High Country News Research Fund.