TWIN FALLS, Idaho — Idaho surface and groundwater irrigators have finalized terms of an agreement aiming to reverse declining Eastern Snake Plain Aquifer levels.
The agreement, reached on July 1, provides a potential longterm solution to a water call filed a decade ago by irrigation companies with the Surface Water Coalition against junior well irrigators with Idaho Ground Water Appropriators, Inc.
Surface users say they’ve been injured by declining spring flows into the Snake River from Blackfoot to Milner Dam, due to the increase in junior well use.
The sides now have until Aug. 1 to convince member districts to participate, or continue facing the risk of curtailment during future dry years.
The agreement seeks to stabilize the aquifer within the next five years and meet its longterm goal of restoring levels to the average fill from 1991-2001 by 2026, according to IGWA attorney Randy Budge. Aquifer levels during the target period were roughly between current lows and peak levels from the early 1960s.
“We were struggling to work out the recovery goal over the last few days,” Budge said. “The experts looked at it and concluded trying to look at one year is probably not the way to do it.”
Under the final terms sheet, well users will be expected to reduce their water usage by 240,000 acre feet per year, about equal to the average annual decline in the aquifer. According to new estimates, the average well user will have to curb water usage by 11 percent per year to meet the goal — slightly less than officials originally calculated.
Nineteen “sentinel” wells have been designated throughout the aquifer to monitor groundwater response to the plan’s implementation.
Budge is optimistic the agreement will be approved by most or all groundwater districts. Participants will be granted safe harbor from curtailment or steep mitigation obligations during future dry years. Twin Falls Canal Co. General Manager Brian Olmstead said it was a risk for his irrigators to consent to safe harbor, but they’ve already ratified the agreement, understanding the importance of protecting the aquifer.
“The only solution is the longterm solution, and that’s why we’ve voted to take the risk,” Olmstead said. “Doing nothing has more risk than anything.”
Thus far, well users have avoided curtailment by providing sufficient mitigation water. They entered into negotiations when it appeared they would fall short this season — prior to an extremely wet May. IGWA Executive Director Lynn Tominaga said his organization has secured the required 110,000 acre feet to meet this season’s debt, despite competition for water with the Bureau of Reclamation, which needed it for flow augmentation.
In future years, IGWA will provide a flat 50,000 acre feet of mitigation water. During wet years, mitigation water will be injected into the aquifer, called recharge, or used for “soft conversions,” switching certain groundwater users to surface water.
IGWA has also agreed to invest $1.1 million annually on soft conversions, when water is available, and has purchased 13,000 acre feet for soft conversions this season.
Furthermore the state has agreed to inject an average of 250,000 acre feet of water into the aquifer annually through an expanded recharge program.