Friday, April 13, 2012

Less water in valley than we thought?

USGS releases study of Wood River Valley Aquifer

Express Staff Writer

Water rushes down the Big Wood River this week. Photo by Roland Lane

There isn't as much water flowing out of the Wood River aquifer as scientists had thought. That's one bit of data included in a long-awaited scientific description of the valley's aquifer released Tuesday by the U.S. Geological Survey.

The new revelation could impact land-use planners' views on the valley's potential for development.

 "The Wood River Valley Aquifer is a priceless gift from nature that, with proper use, can provide a sustainable water supply for generations of Blaine County residents into the future," said USGS Director Marcia McNutt in a news release. "USGS science is helping to understand the size and complexity of this magnificent underground system so that those whose lives depend on it can make wise decisions."

Called a "hydrogeologic framework," the work defines the extent, physical characteristics and hydraulic properties of the aquifer system that supplies the valley's groundwater. Details were derived from well-drilling reports, geologic maps, previous studies and new geophysical surveys.

"Scientists found that the aquifer system ranges in thickness from less than a foot to about 350 feet thick in the southern part of the Bellevue Triangle," said Jim Bartolino, a USGS groundwater hydrologist, in an interview.

Bartolino said the aquifer system is composed of sediment and basalt.

 The study is being conducted in partnership with Blaine County, local cities, The Nature Conservancy, the Sun Valley Water and Sewer District, and the Blaine Soil and Conservation District. In order to secure federal dollars, half the Wood River project budget comes from local sources. So far, the project has cost about $250,000 in local funds, with the final phase, a study of water quality, now underway.

The local aquifer, like others in the area, including those in the Little Lost and Big Lost drainages, feeds the larger Eastern Snake Plain Aquifer, comparable in size to Lake Erie. The new report estimates that some 4,000 acre-feet of water is passing through the local aquifer beneath Silver Creek and on to the Eastern Snake Plain Aquifer each year. That's considerably less than had been estimated in earlier University of Idaho and USGS reports that said between 11,800 acre-feet and 58,000 acre-feet per year were passing out of the local system.

Reasons for the difference are up for investigation. In any case, the new USGS studies will help scientists uncover the impact of human consumption on the dynamic system.

Wendy Pabich, a Hailey-based water scientist who has long been involved in water planning, research and policy decisions in the Wood River Valley, is one of three scientists who helped to jump-start the multi-year, multi-phase USGS study that got underway in 2006.

"Understanding the variability in the geology and the available water across the system has implications for planning questions," Pabich said.

Pabich suggests the USGS work will help policy-makers answer questions such as "How many houses should be in the valley's tributary canyons? And, "How many houses can the underlying aquifer support?"

Blaine County Commissioner Tom Bowman said he is looking forward to using the new tools at hand to answer such questions.

"When viewed as a community investment, this benchmark study will continue to pay dividends of truly informed development decisions in the Wood River Valley for decades or perhaps centuries to come," Bowman said.

Bartolino said the new data are now being used to help develop an accurate groundwater-flow model of the aquifer. This summer, he said, his team will also be gathering data on water quality throughout the aquifer.

"This is only getting done because the people in the Wood River Valley have been so supportive," Bartolino said. "I have rarely seen a community that is so curious and concerned about getting a handle on the information about their water system."

A meeting at the Blaine County Courthouse is scheduled for Wednesday, April 25, to give public officials and the study's financial backers a chance to learn more about it. More information about the multi-phase Wood River Valley groundwater study is available on the USGS website at

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