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Drought, Consumptive Uses Lowering Wood River Valley Water Levels
Released: 2/18/2009 10:54:40 AM

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
James R.  Bartolino 1-click interview
Phone: 208-387-1392

Tim Merrick 1-click interview
Phone: 208-387-1305

REPORTERS: Results will be presented at two meetings on Feb. 24. See second page for details. 


Drought and water consumption are lowering water levels in Idaho's Wood River Valley, according to a water budget study released by the U.S. Geological Survey (USGS).

The Wood River Valley depends on its ground water for everything from irrigation to domestic uses to adequate flows in its rivers and streams.

The study examined the sources and amounts of recharge to and discharge from the aquifer system. The USGS study focused on three time periods: the decade from 1995 through 2004, the relatively wet year of 1995, and the relatively dry year of 2001.

Study results show that the aquifer is very responsive to drought. More than half of the water that recharges the aquifer runs down mountain canyons that are tributary to the Big Wood River. During wetter years, recharge exceeds discharge, which means that more water is stored in the aquifer. Because the valley's aquifer and its streams are interconnected, higher ground-water levels contribute to increased streamflows. However, during drier years, more water is discharged from the aquifer than is recharged to it. Consequently, ground-water levels and streamflows decline. These findings reinforce the results of a USGS study released in December 2007 that revealed a trend toward declining ground-water levels in some parts of the Wood River Valley.

The new study also shows that the valley's per-capita water usage is significantly greater than the average for Idaho communities. Some of that greater usage may be accounted for by the numerous properties owned by non-residents, who are not counted in the local census. The reported water usage includes both consumptive uses, such as lawn irrigation, and non-consumptive uses, such as household use.

As in many areas of the American West, residents are concerned about how the conversion of agricultural land to urban uses affects hydrologic systems. The USGS study estimated the average consumptive water use for three categories: agricultural, urban, and undeveloped. In general, the study found that, per acre, most urban land uses in the Wood River Valley consume slightly less water than agricultural uses consume. In addition, the estimated amount of water being pumped from the aquifer by the four valley municipalities is less than 10 percent of the amount estimated for irrigation and pumpage from privately-owned wells.

The report, which is available online at http://pubs.usgs.gov/sir/2009/5016/, completes the second phase of a proposed four-phase USGS assessment of ground-water resources in the Wood River Valley. The next proposed phase will examine the geologic framework of the aquifer to provide a better understanding of how water moves through the system. The USGS is conducting the assessment in cooperation with Blaine County and a consortium of valley cities and organizations.


Reporters may attend either of two meetings on Feb. 24 during which USGS scientist Jim Bartolino will present the water-budget study results and an overview of the proposed geologic framework study.


Time:               10:30 a.m.

Location:         Old Blaine County Courthouse, Hailey, ID


Time:               6:00 p.m.

Location:         Ketchum City Hall, Ketchum, ID

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