Although Ecology said the ban was necessary to protect surface water rights, the agency hasn't proved that domestic wells affect aboveground water. Officials expect a forthcoming U.S. Geological Survey study to define the extent to which groundwater interacts with rivers and streams in the Yakima Basin. But the study doesn't address groundwater dynamics in the bedrock aquifers that predominate in upper Kittitas County, where the drilling ban is in place. Still, says Tebb, Ecology believes that most groundwater there flows into the Yakima or a tributary, and that surface waters in the upper county are especially sensitive to groundwater pumping. The area is home to the basin's headwaters, and because of its mountainous topography, development tends to occur closer to streams.

However, without hard evidence to support a drilling ban, general contractor Steve Senger says it is economically indefensible. Senger estimates he's lost $3 million in business since July. He's laid off five of six full-time employees, including one of his daughters, and reduced the sixth's hours. "(The ban) has pretty much devastated the construction industry in upper Kittitas County," he says.

The construction industry is the area's third-largest employer, behind state and local government, according to County Commissioner Mark McClain. The county legally supports developers' use of exempt wells to serve multiple homes, he says, because even groups of homes are still only allowed to pump 5,000 gallons of water a day. But, as in most of the West, no one is metering the wells to see how much they're actually pumping.

"If you don't meter them, you surely can't manage them," says Gary Woodard of the University of Arizona. That's why Woodard is seeking volunteers to participate in a well-metering study in Cochise County, Ariz., where there are about 10,000 exempt wells. Most new wells in the county are going in close to the San Pedro River, which ran dry in 2005 partly because of groundwater pumping and growth. Those wells may actually be drawing surface water or intercepting groundwater on its way to the river, says Woodard, but without metering, their impact is hard to pin down. Despite offering anonymity, Woodard has had trouble recruiting volunteers. He says people assume meters will lead to limits on their water use.

"Folks that are out there in these rural areas, they like to be left alone," he says. "And they've got a sizable investment in their well system."

Indeed, limiting exempt wells, especially in the high-growth areas where tighter controls are most needed, is a politically thorny endeavor. Property-rights advocates typically oppose restrictions, and development is a significant economic engine in the rural areas where exempt wells have become controversial. Legislatures are hesitant to touch the issue. In New Mexico, where domestic wells require permits but are not subject to regulation under prior appropriation, bills are killed almost annually. The same is true in Arizona, which has few regulations on rural groundwater pumping.

In the Washington Legislature this year, a bill died that would have required metering of new exempt wells and limited to six the number of homes that could hook up to a single well. In the absence of such reform, the Department of Ecology's authority to regulate domestic wells remains unclear. The attorney general recently issued an opinion permitting the agency to close over-appropriated basins to exempt wells, but not to change the terms of the exemption. Ecology cannot lower the daily withdrawal limit below 5,000 gallons, for instance; only the Legislature could do so.

In the wake of that opinion, Ecology officials expect existing rules that limit exempt wells to stand. In the Walla Walla Basin, for example, new homes and developments in high-density areas are required to connect to municipal water systems whenever possible, new exempt wells are metered, and outdoor watering is mitigated.

But the agency is uncertain about the status of rules it's currently negotiating with county governments. If things aren't settled in Kittitas County, many see litigation on the horizon. The basin's most senior water-rights holders, like the Yakama Nation, could take the state to court at any time to cut off exempt wells during drought. If they succeeded, a lot of people who thought they had a reliable water source could be left high and dry. "We're going to have a water war," warns Osborn. "You can just see the knives are sharpening."  

This article was made possible with support from the Kenney Brothers Foundation.