Pumping the San Pedro dry?


Arizona’s San Pedro River has been called the most studied river in the world, attracting scientists, birders, and anyone wanting to observe the region’s healthiest desert river. But all that research doesn’t seem to have affected an April decision by the Arizona Department of Water Resources to approve groundwater pumping that could deplete the river’s water.

The saga started six years ago, when a California developer proposed Tribute, a huge development in Sierra Vista, a fast-growing desert city an hour south of Tucson. As Tony Davis reported in his February HCN story, “Standoff on the San Pedro,”

Plans call for nearly 7,000 homes and apartments, plus offices, shopping, parks and schools. The real estate bust has temporarily derailed it, but eventually up to 250 homes a year could be built.

State water law requires developers to prove they have a hundred-year supply of groundwater for new projects, and since the 1970s, the state water board has consistently found that developers meet that requirement. The Tribute project was no exception: last July, the Department of Water Resources determined there was indeed enough groundwater for the project to meet its annual 3,300 acre-foot appetite for the next century.

San Pedro River
That finding appears to contradict the myriad studies that document the connection between the water that flows in the San Pedro and the groundwater beneath it.

As Davis reported,

Pumping creates a "cone of depression" that depletes the water table, and many hydrologists and environmentalists believe that excessive groundwater withdrawals could eventually empty much of the San Pedro…

Many studies since the 1980s predict that the water table could drop so far that it would no longer support a year-round flow, killing cottonwood and willow trees and harming riparian habitat. A 2011 study found that groundwater pumping already has reduced the river's flow somewhat.

Based on those studies, members of the Tucson-based Center for Biological Diversity (CBD) and the Huachuca Audubon Society appealed the water board’s July 2012 decision to allow the development to go forward. The Bureau of Land Management joined the appeal to protect Congressionally-granted federal water rights to surface water in the San Pedro, which runs through a National Conservation area the agency manages.

But Arizona water law doesn’t recognize the relationship between ground and surface water, and the state water board has said before that it lacks the ability to stop groundwater pumping to save the river. “As scientists, we all recognize that connection, but in court it’s a different set of rules,” said Ben Lomeli, a hydrologist at the Bureau of Land Management’s Tucson field office. As a result, an administrative judge dismissed the appeals in March, allowing the Department of Water Resources to go ahead and approve the Tribute project (again) earlier this month.

Now, environmentalists say they’re going to take the Department of Water Resources to the Arizona Superior Court over the decision. Robin Silver, a founding member of CBD, and Tricia Gerrodette, president of Huachuca Audubon Society, both said they are working with lawyers to craft another appeal over the water board's decision, which must be filed before mid-May. The BLM won’t say what its next step is, but Lomeli said the agency is reviewing the case.

“This case is huge, and not only for the San Pedro,” said Silver. “It has precedence for any federally supervised lands that have water rights being challenged by the malfeasance of the state.”

Emily Guerin is the assistant online editor at High Country News.

Photo courtesy Flickr user detritus.

This post was updated at 3:17 p.m. on April 24 to reflect the correct volume of groundwater pumping by the Tribute project.

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