Two new state water projects in Idaho will help slowly refill the depleted East Snake Plain Aquifer in the coming decades, officials say.
In high-water years, a recently completed $1 million canal in the Egin Bench area of Fremont County in eastern Idaho will funnel water from the Henrys Fork of the Snake River to a porous basin, where it will sink into the ground.
The other major project, barely finished in time for the 2016 irrigation season, was the $1.4 million construction of new headgate for the Great Feeder Canal, the large canal system branching off from the South Fork of the Snake River east of Ririe. That project also will help state water managers ramp up aquifer recharge sites in the coming years.
The projects are part of a statewide effort by the Idaho Department of Water Resources to replenish the aquifer through managed recharge, a method of allowing surface water to seep through certain porous areas of ground and into the aquifer. The massive underground reservoir has been on the decline for decades due to pumping and other reasons, sparking frequent battles over the water that remains. Recent drought has exacerbated the problem.
The state’s goal by 2020 is to recharge as much as 250,000 acre-feet of water annually back into the aquifer. To get there, recharge infrastructure and sites will need to be scaled up dramatically, officials say.
This past winter, total recharge efforts backed by the state—all located in south-central Idaho’s the Magic Valley area—came to just 66,000 acre-feet of water, said Wesley Hipke, the state’s recharge project manager. That is slightly down from about 74,000 acre-feet last year, he said, partly because more water had been available last year for recharge in the Upper Valley.
Egin Canal
The state paid the full $1 million to build the new 2-mile Egin canal. State officials will have full control over using it when sufficient water is available to use for recharge, Hipke said.
“If and when there’s recharge water available, it’s ready to accept it,” said Jeff Raybould, who grows potatoes next to the canal and is a member of the Idaho Water Resource Board. “In a good water year it’ll allow us to recharge an additional 250 acre-feet per day over and above what the former system (could handle).”
The previous canal could accept about 50 to 60 acre-feet per day, he said. The Egin area is ideal for recharge, Raybould said, because water recharged there has been shown to remain in the aquifer longer than water from other recharge sites.
Great Feeder Headgate
The state paid $500,000 to help replace the headgate on the Great Feeder Canal, with the canal company by the same name covering the remainder of the cost.
The new gate will help better control and measure the flows going into the canal system and address leakage problems. The headgate was last upgraded in the 1960s. The new version will help the state more precisely control how much water is sent into the canal system for recharge efforts, Hipke said, as well as help the canal company in delivering water to irrigators.
The next step is to set up several recharge sites along the dozens of canals supplied by the Great Feeder, said Water Board chairman Roger Chase. He said state officials have been looking for ideal locations to conduct recharge next to the canals, and they have so far found eight locations where water would easily be diverted from a canal and seep into the aquifer. Some of the potential recharge sites are former gravel pits.
Chase said the recharge sites could potentially be ready to accept water by next spring.
The bulk of recharge efforts in the coming years will continue to occur below American Falls, where the state is consistently allowed to take water for such efforts, Hipke said. Sites upstream are more dependent on years where there is flood water on hand. But those upper recharge sites are crucial to have in place, too, officials say; otherwise, extra water will flow past in the rivers, unused.
“We need to [have] more recharge sites so that in the years where there’s big water, we can reach our goals,” Chase said.
Source: Idaho Falls Post Register