Idaho’s recharge program will fall short of its annual volume goal, according to its manager.

Replenishing drought-depleted reservoirs has left less water available to return to the Eastern Snake Plain Aquifer, said Wesley Hipke, who manages the recharge program for the Idaho Water Resource Board. 

However, the current recharge season is stretching longer than usual, which likely will benefit the aquifer in the long term.

High snowpack in the central mountains means operators of Magic Reservoir, on the Big Wood River, continue to release water. That is expected to continue until about June 23, said Hipke.

“If that goes as planned, we would hit about 144,000 acre-feet” of recharge systemwide, he said.

Though that total falls well short of the board’s 250,000-acre-foot annual recharge goal, the added volume in the Big Wood system “has a long-term benefit to the ESPA,” Hipke said. “It stays in the aquifer a long time and really helps during long, dry periods.”

Above-average snow and rain in the 2022-23 water year benefited Eastern Snake Plain reservoir levels, soil moisture and the aquifer, he said.

“It just didn’t provide a lot of extra for recharge,” Hipke said.

Nevertheless, Magic’s strong supply is welcome because often that reservoir does not fill — as was the case in each of the last three years — and because it extended the aquifer-recharge season past its usual late March conclusion.

Low reservoir carryover following the 2022 irrigation season left less water available for recharge, Hipke said.

Physical storage in Upper Snake River reservoirs is expected to peak at 90% full, up from the 62% peak in 2022, according to the U.S. Bureau of Reclamation.

Aquifer levels declined over the years for reasons including population and business growth, and more efficient irrigation that returns less water to the ground.

The Water Resource Board started its annual recharge program in 2014. Recharge volume has averaged 236,000 acre-feet per year, Hipke said. Last year’s total was about 247,000 acre-feet.

The board has added more than 2,000 cubic feet per second of recharge capacity since 2014. A cubic foot per second amounts to 1.98 acre-feet per day.

“Since ’14, we have had four wet years and five dry years,” which “speaks to the need to develop even more capacity so that when more water is available, we can put more water into the aquifer to help sustain us during these dry periods,” Hipke said.