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Recharging the East Snake Plain Aquifer

The Eastern Snake River Plain Aquifer extends from St. Anthony to Twin Falls and King Hill. It is 170 miles long, and as wide as 60 miles. The aquifer is made of mostly broken basalts. Like a giant sponge, this broken basalt holds water. As deep as 4,000 feet, water flows most easily in the upper few hundred feet. If you could squeeze all of the water out of the Aquifer you would have as much as a billion acre feet of water, which is enough to cover the entire Plain with 140 feet of water.

Unfortunately, the water in the Eastern Snake River Plain Aquifer has been declining. Much of the decline in the Aquifer has been attributed to farmers in Eastern Idaho that pump groundwater for irrigation purposes.

Several years ago surface water irrigation districts in the lower Snake River Plain made a delivery call on upper Snake River Plain groundwater users, most of which had later priority dates. (Idaho law: First in time is first in right) In an effort to avoid an order from the Idaho Department of Water Resources that would have shut off some groundwater users entirely, the groundwater users in Eastern Idaho collectively agreed to voluntarily reduce their consumption of groundwater. Groundwater users also agreed to monitor ground water levels and to put flow meters on groundwater pumps.

Groundwater users additionally agreed to work with the State of Idaho in an effort to recharge the Aquifer with as much as 250,000 acre feet of water annually. Several recharge projects have begun. Some canal companies are now receiving revenue for doing recharge during the off season. The goal of the agreement between groundwater users and surface water users is to gradually increase groundwater levels throughout the Aquifer.

The settlement agreement between the surface water coalition and the groundwater coalition is a legally binding contract. Working together on recharge projects surface water users and groundwater users hope to protect and sustain one of Idaho’s greatest treasures – its water!

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