Study shows drop in water levels in Carson Valley wells
Nevada Appeal News Service
Water levels in wells have dropped to a level five to 10 feet below the level they sustained after the 1982-92 drought in the Johnson Lane, Fish Springs and Ruhenstroth areas, according to Doug Maurer, hydrologist with the United States Geological Survey.
Increased development or drought conditions could be the cause, Maurer said.
“The drought from 1999 to 2004 was more severe than in 1992 and the effects of the wet years in 2005 and 2006 may take time to be seen,” he said. “We’re still not sure.”
Water levels in East Valley have declined about 20 feet below 1992 levels after the old Dangberg Reservoir was drained, but along Buckeye Creek, water levels are rising. Officials attribute the rise to effluent leakage from the storage reservoir, according to Maurer.
In other areas of the valley floor, western alluvial fans and flow from artesian wells are subject to fluctuations with summer pumping, but are otherwise fairly constant, according to Maurer.
The statistics, which will be used to evaluate potential effects of changes in land and water use in Carson Valley, are part of a preliminary report that should be released in the next few weeks, Maurer said. It should include figures concerning the recharge rate, critical to the determination of a much-anticipated growth cap in Carson Valley.
The annual recharge rate measures the water added to the water table each year and has been estimated at 35,000 acre feet, that number from a report completed in the 1980s.
Groundwater inflow from the surrounding mountains, just one facet of this recharge, is estimated to average between 22,000 and 39,000 acre feet per year, according to this report.
“There’s also streamflow losses and part of the water that’s pumped percolates back into the water,” Maurer said. “We’ve made estimates of that, but we shouldn’t release them until the report is approved.”
The study includes Carson Valley from the upper reaches of the Sierra Nevada to the Pine Nut Mountains. In addition to measuring water levels in 70 wells scattered throughout the valley, the study includes precipitation and transpiration rates from plants in the valley.
Data indicates an estimated 270,000 acre feet pours into to the Carson Valley each year from precipitation, and another 37,600 acre feet through tributary inflow, but only a fraction of that is added to the water table.
Irrigated alfalfa fields consume about three feet, and regular pasture three to four feet per acre annually. Pastures that are not irrigated, sage and greasewood consume about 1.7 feet per acre.
This preliminary report, which is waiting for approval, should include a more definitive recharge rate. The State Engineer will provide the pumping inventory from domestic use, to be added to the upcoming report, Maurer said.
A final report, which will update water compliments and determine the geographic distribution of recharge, is expected in 2008.
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