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EDEN — A structure to divert water on the Milner-Gooding Canal is nearly complete, putting recharge efforts in the Middle-Snake region of the Eastern Snake Plain Aquifer right on schedule.

“And it’s a very aggressive schedule,” said Wesley Hipke, recharge project manager with the Idaho Department of Water Resources.

The state has installed an Obermeyer weir — an inflatable dam with pneumatically operated spillway gates — across the canal, and constructed slide gates above the weir to release water into the Milepost 31 recharge basin north of Eden.

The $2 million project, an expansion of a prior recharge project at the site, is part of Idaho’s effort to replenish the depleted ESPA, shrunk to its lowest level from decades of groundwater pumping.

The state’s long-term goal is to artificially recharge an average of 250,000 acre-feet per year into the aquifer. Milepost 31, operated by American Falls Reservoir District No. 2, so far has the largest capacity of any recharge site in the state.

The Idaho Water Resources Board has a window of about 120 days each year to divert surface water into the aquifer, using 1980 recharge water rights from the Snake River.

A minimum of 500 cubic feet per second flow over Minidoka Dam is required during the winter for endangered snails, Hipke said.

“This is water that would leave the state if not used for recharge,” he said.

To date, Milepost 31 has sent 13,000 acre-feet into the aquifer since the end of the irrigation season, at a rate of 200 to 250 cfs from the original point of diversion, just upstream from the new facility. The water is diverted from the Snake River at Milner Dam.

In about a week, an additional 400 cfs will flow through the new facility, said Lynn Harmon, manager of American Falls Reservoir District No. 2, an umbrella district encompassing the Milner-Gooding Canal and Big Wood Canal systems. The site should be able to handle up to 600 cfs when there is enough water in the system.

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Hipke expects 87,000 acre-feet of recharge at Milepost 31 by the start of the 2017 irrigation season.

Twin Falls Canal Co., North Side Canal Co. and Southwest Irrigation District are also major participants in ESPA recharge. Total recharge for the winter is expected to be reach 100,000 acre-feet, compared with 68,000 acre-feet recharged last winter. That’s 40 percent of what the state wants in the long run.

“I’m pretty confident (we’ll get it),” Hipke said. “We wont know until we can actually put water out there.”

“This is water that would leave the state if not used for recharge.” Wesley Hipke, recharge project manager with the Idaho Department of Water Resources

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