New Plan May Slow Demise of Critical Aquifer

Jul 3, 2015

A huge, sole-source aquifer in southern Idaho is shrinking under the onslaught of drought and heavy irrigation, But a new agreement among water users may head off contentious battles over shares of the critical resource.

An agreement hammered out this month between ground-water and surface-water users in the Snake River aquifer seeks to stabilize the underground reservoir by cutting well water use and by pumping some ground water back into the aquifer to re-charge it.

Still, the big aquifer - it covers roughly 200 by 60 miles underneath valuable agricultural land in southern and southeastern Idaho - is dropping rapidly.

A new survey by the US Geological Survey found that water levels fluctuate sharply - nearly five feet seasonally - and they've dropped as much as 25 feet over the past 14 years. Last year, Snake River aquifer levels hit all-time lows.

In fact, the agency said that two monitoring wells on the Idaho National Laboratory went dry in the past year, and water levels at several other wells are barely above the pump heads.

Irrigators are also worried about shrinkage of the aquifer - not for radioactivity monitoring, but for crop damage. The new pact requires well users to cut their water usage by 240-thousand acre feet a year, about 11 percent of normal.

Additionally, the Idaho Department of Water Resources will inject another 250-thousand acre feet of water into the aquifer each year using Snake River flow and natural seepage from unlined irrigation canals.