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Idaho aquifer recharge headed for another big year

This year’s recharge efforts are expected to put 370,000 acre-feet into the aquifer, surpassing last year’s record of 317,000 acre-feet.
Carol Ryan Dumas

Capital Press

Published on February 22, 2018 9:37AM

Courtesy Idaho Water Resource Board
Water is recharged at the milepost 31 site near Shoshone this winter. The site is the biggest workhorse in the recharge system.

Courtesy Idaho Water Resource Board Water is recharged at the milepost 31 site near Shoshone this winter. The site is the biggest workhorse in the recharge system.

Courtesy Idaho Water Resource Board
Water is recharged at the Great Feeder site on the South Fork of the Snake River northeast of Idaho Falls. Those recharge flows go down canals and seep into the aquifer.

Courtesy Idaho Water Resource Board Water is recharged at the Great Feeder site on the South Fork of the Snake River northeast of Idaho Falls. Those recharge flows go down canals and seep into the aquifer.


The Idaho Water Resource Board has already recharged more than its 250,000-acre-feet annual goal this winter into the Eastern Snake Plain Aquifer and expects to reach 370,000 acre-feet by spring.

That would eclipse the record 317,000 acre-feet recharge last year.

Abundant precipitation last year led to the record-level recharge and kick-started this year’s efforts, with 61,000 acre-feet of surplus water donated by the Surface Water Coalition recharged beginning in late August.

In addition, a big surplus of water stored in Upper Snake River reservoirs caused the U.S. Bureau of Reclamation to release more water than usual this winter below Minidoka and Milner dams.

More than 115,300 acre-feet of water has already been recharged in the Upper Snake region, and more than 138,343 acre-feet has been recharged in the Magic Valley region.

The Water Resource Board is working to help restore the aquifer to sustainable levels, with a goal of recharging an average of 250,000 acre-feet a year.

Together with a commitment from the Idaho Ground Water Appropriators to reduce water use by 240,000 acre-feet a year through its agreement with the Surface Water Coalition, the board expects to bring the aquifer into balance for long-term viability.

When that will be accomplished depends on what one considers to be “balance,” said Wesley Hipke, IWRB recharge project manager.

It’s not realistic to return aquifer levels to the peak of the 1950s, when inefficient irrigation methods and wetter water years had it elevated to levels of more than 18 million acre-feet, he said.

The benchmark in the agreement between surface and groundwater users is to bring it to average levels between 1991 and 2001 by 2026, he said. Starting at a level of about 5 million acre-feet, the goal is to get cumulative storage to about 8 million acre-feet, he said.

The aquifer has been overdrafted by an average of 200,000 acre-feet per year since the 1950s, and it’s a huge ship to turn around, he said.

“It’s imperative to recharge as much water as possible during these surplus years, and it’s equally important in dry years,” he said.

Despite a couple of minor upticks, the aquifer has been on a pretty steady decline since the 1990s. Last winter’s abundant water supply provided the first notable uptick, showing a gain of 660,000 acre-feet year over year in March of 2017, he said.

That gain was likely higher, however, as recharge efforts continued until the first of July and natural recharge was also likely extended beyond normal, he said.

“The big question is what happens in the future and how long it (the gain) stays around,” he said.

This year is going to be another good year for recharge, but there’s more work to do to build infrastructure to capture available water, he said.

Had planned additional recharge infrastructure been in place under last year’s conditions, the board could have recharged 500,000 acre-feet — and that’s the goal going forward,

“In these big years, we need to get a lot more of it into the ground,” he said.

There have been years where the board was only able to recharge 150,000 acre-feet. Capturing more in the big water years would help make up that deficit, he said.



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