FORT HALL, Idaho — Idaho Ground Water Appropriators Inc. has agreed to lease 45,000 acre-feet of storage water over five years from the Shoshone-Bannock Tribes to help meet a requirement of a recent settlement agreement with the Surface Water Coalition.
The agreement, reached last summer, requires junior Eastern Snake Plain Aquifer groundwater users to give the coalition a flat 50,000 acre-feet of mitigation water annually.
The seven coalition members filed a water call about a decade ago, arguing junior well irrigation has contributed to the decline of springs that supplement surface flows in Snake River reaches between Blackfoot and Milner Dam.
Prior to the agreement, IGWA’s annual obligation fluctuated based on the water outlook, and groundwater users risked curtailment if they failed to find the necessary water during an especially dry year.
IGWA members have also consented to reduce their yearly water consumption by 240,000 acre-feet — equal to roughly a 13 percent reduction per groundwater user, varying by priority date and other factors.
IGWA Executive Director Lynn Tominaga said the water will come from tribal storage rights in the American Falls and Palisades reservoirs. It must be delivered to the coalition within a few weeks of when the final mountain snowpack melts, known as the “day of allocation.”
The tribes previously leased the water to Idaho Power, which used it for hydropower production and had allowed the water to run downstream of Milner without being put to an irrigation use. Idaho Power can now produce electricity more cheaply from its Langley Gulch gas-fired peaker plant. Tominaga said IGWA paid the “market rate” for the water, but the precise amount is confidential.
Brian Olmstead, general manager of Twin Falls Canal Co., said he’s pleased the tribal water will now be used for irrigation.
“I’m sure it wasn’t cheap, but it’s really the only block of water left that hadn’t been allocated for irrigation,” Olmstead said.
Furthermore, he said the water has an old water right that’s in priority virtually every year, providing IGWA with certainty in even the worst of drought years.
In wet years in which there’s ample storage carryover, Olmstead said the coalition will use the water for managed aquifer recharge — injecting water into the aquifer to reverse declines.
In drought years, the coalition will award IGWA’s water to the members that need it most, which Olmstead said could mean the difference between drought-stressed and healthy crops. Olmstead said his company has 42 percent of the coalition’s water rights, but relies heavily on natural flow rights rather than storage.
“We’re going to be one of the first ones injured, and most of the time injured the largest, in a drought year,” Olmstead said.