About 379,000 acre-feet of water recharged into aquifer

By Steve Stuebner

Idaho Department of Water Resources

BOISE – The Idaho Water Resource Board in early June was finalizing multi-pronged efforts over the winter of 2023-24 to send Snake River surface water flows into the Eastern Snake Plain Aquifer to help restore the aquifer to sustainable water levels.

The board relied on a record number of new and existing aquifer-recharge sites throughout the Eastern Snake Plan Aquifer region to boost recharge flows, officials said.

“Once the water turned on in the Upper Snake, we’ve really been able to crank up the recharge flows,” said Wesley Hipke, ESPA recharge program manager for the board. “Big picture, it was nice to not only hit our recharge goal this year, but also exceed it with a record number of recharge sites being utilized throughout the basin.”

In late March, when the Bureau of Reclamation and Army Corps of Engineers were releasing flood-control flows out of Upper Snake reservoirs, recharge flows increased to 4,000 cubic feet per second per day, allowing the board to turn on 12 different recharge sites above American Falls Reservoir, Hipke said. Once irrigation deliveries started, the capacity for recharge was reduced but recharge continued until May 29.

Overall ESPA recharge flows occurred for 230 days at 18 sites, with an average flow of 901 cfs, Hipke said.

Summary for the IWRB 2023/2024 recharge season:

• Started natural flow aquifer-recharge on Oct 28. Ended natural flow recharge on May 29.
• The total natural flow recharge volume is estimated to be 379,081 acre-feet of water for the winter 2023-24 season.

How does the aquifer-recharge program work?

The board partners with irrigation districts and canal companies in the ESPA region to run Snake River surface water into canals to reach aquifer-recharge basins, where the water sinks into the aquifer.

The board has an existing water right for the purpose of ESPA recharge, which comes into play after the end of the irrigation season.

Besides the board’s natural flow recharge program, staff assisted the cites, Surface Water Coalition (SWC), Idaho Ground Water Appropriators and other entities to recharge more than 90,000 acre-feet of water into the ESPA as part of the SWC settlement agreements. This recharge occurred between Oct. 6 and Nov. 15.

Other program highlights:

• Due to increased recharge capacity developed by the board and its partners, a new maximum recharge diversion rate of more than 4,000 cfs occurred during peak flows in March and April.
• The board had minimal flows for much of the winter season – about 500 cfs. Increased flood-control releases started on March 22, providing increased water for recharge and allowing for aquifer-recharge in the Upper Snake region, above American Falls Reservoir.
• The board utilized the Big and Little Wood river flows for aquifer recharge between Feb. 22 and May 10.
• Two new recharge facilities that were utilized this year include New Sweden, Idaho’s Basalt and the Enterprize Canal Co.’s 55th Road recharge sites.
• The board has two other sites being constructed near the South Fork Snake River that are scheduled to be completed by next winter.
• Board staff are working with numerous entities in the Upper Valley to develop more recharge sites.

For more information about the board’s ESPA recharge program, go to: https://iwrbrecharge-idwr.hub.arcgis.com/.