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San Pedro River is running dry

ALONG THE SAN PEDRO - A key stretch of the last free-flowing river in the Arizona desert has run dry for more than three days, for the first time in at least 75 years. Since Saturday afternoon, no water has coursed down the San Pedro past a measuring station about seven miles northeast of Sierra Vista - the flash point of one of the Southwest's hottest growth-water conflicts of the past 20 years. Other parts of the river have dried at times since surveyors started keeping sporadic records early in the 20th century, and continuous records since 1930. But the Charleston area has always been closely watched because it has impervious bedrock close to the surface, making it very likely to have running water. The San Pedro's fate has been passionately debated, sued over and studied. The river is home for up to 300 bird species. As many as 6 million birds stop there each year while migrating back and forth from Latin America to Canada. The San Pedro is also a ribbon of green, lined by huge colonies of cottonwood and willow trees, running north from Mexico to Benson and beyond. Conservationists and some federal agencies have warned since as early as 1960 that Sierra Vista's growth and water pumping could cause the San Pedro to dry as did the Santa Cruz River through Tucson. Tuesday, some environmentalists and researchers said, in effect, "I told you so." Others said other factors may have caused the drying and that Sierra Vista is doing a lot to conserve water now. The immediate causes of the decline could be delayed monsoon rains and trees draining the water table, but pumping could be a long-term cause, said Don Pool, a U.S. Geological Survey hydrologist. No scientific studies exist documenting changes in riverfront vegetation. Satellite photos have shown minor increases, Pool said. Thomas Maddock is a University of Arizona scientist who warned in 1993 that his studies found pumping could dry up the river in 10 to 15 years. Now UA's hydrology department chair, Maddock said Tuesday that drought and trees may have been a factor in the drying, but the presence of a major pumping center such as Sierra Vista "can't help but affect it.'' While monsoon rains will put water back in the river, if population and pumping keep rising, a dry river will become more common and eventually the norm, Maddock said. He doesn't look forward to visiting the river in its current state because "it will break my heart." Bob Strain, chair of an advisory committee for the Upper San Pedro Partnership, said Tuesday that "we wouldn't be having this conversation if the monsoons were starting on time." But he said the drying is a concern both because it could cause an overreaction by people, leading to bad decisions, and because the partnership exists to protect the river and the area's economic health. "Do we have answers? No," said Strain, whose group represents governments, a developer and nonprofit groups. "Is the Charleston gauge the canary in the coal mine? Many will think so. I honestly don't know." Sierra Vista's population grew by 7 percent since 2000 to more than 40,000 people by 2004. The metro area could approach 100,000 by 2030. But Sierra Vista's daily water use dropped from 172 to 157 gallons daily per person from 2003 to 2004, probably because of conservation, said Marie Hansen, a city spokeswoman. The city's total water use dropped by 286 acre feet that year. That doesn't account for the widespread unregulated development outside the city. Many of those homes rely on wells whose total use isn't known. The area's private water companies reported a 13 percent water pumping increase from 2000 to 2003, on top of 40 percent growth from 1990 to 2000. Robin Silver, a Phoenix environmentalist who has fought to save the San Pedro for more than a decade, said the river has already recovered from droughts, cattle grazing and significant agricultural groundwater pumping. But the river has never faced so much urban groundwater pumping, he said. "It's an incredible challenge," he said.