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BISBEE - If a citizens' forum was expecting to know why the San Pedro River went dry at the Charleston gauge in July, a U.S. Geological Survey hydrologist had no answer on Tuesday.
While no water flowed past the gauge for the first time in recorded history, Jim Leenhouts could only say there are a number of things happening with the river that together may have caused the problem.
While there has been finger-pointing at different culprits, Leenhouts said the only given is "this is the first time of zero flow" at a gauge that has measured water going by it for 70 consecutive years, he told members of the Southeast Arizona Citizen's Forum of the U.S. International Boundary and Water Commission on Tuesday at the Bisbee City Hall.
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He listed a number of possible reasons for part of the early July no flow, including increased groundwater pumping due to growth, drought, a change in how the riparian area is working and the late start of the monsoon.
In the early afternoon of July 6, less than a quarter of a cubic foot per second was going by the gauge, he said. A cfs equals 7.5 gallons of water going by a point every second.
"By 7 p.m. (July 6), it was completely dry, no flow," Leenhouts added.
There were a couple shallow pools of water in the area, but absolutely no stream flow, he said.
The USGS, Bureau of Land Management, The Nature Conservancy and other groups are meeting to see if the reason, or reasons, can be found, Leenhouts said.
The vegetation along the river and the resulting evapotranspiration could be a player as well, he said.
It is true over the years there have been downward trends in the flow of the river with the summer months recording the most drastic decrease, Leenhouts said.
But here is even a decline in winter flows, a time when trees shut down, consuming less water, he added.
Ben Lomeli, a former BLM hydrologist and a member of the forum, said he and others warned a decade ago that the river would go dry.
That was nine years ago. He reminded everyone there is only a year left in the prediction. Lomeli was an outspoken critic of water use in the Sierra Vista Subwatershed, especially the increase in groundwater pumping.
Noting that in the past there has been a desire to build a major dam in the Charleston area of the river, an idea still popular among some people, Lomeli said it is a bad idea.
"It would be an environmental disaster, trading a river for a lake," he said.
Leenhouts agreed that a dam is not the answer.
Coming up with a solution still requires a better understanding what is happening with the river and its riparian area and how all the problems fit into the puzzle, he said.
In some cases, the available scientific information is at odds, Leenhouts said.
"I don't think it's a simple issue. There's no single reason," he said.
HERALD/REVIEW senior reporter Bill Hess can be reached at 515-4615.
shuni wrote on Apr 18, 2008 12:11 AM: