The Idaho Department of Water Resources (IDWR) has determined the Twin Falls Canal Co. may face a water shortfall of 75,300 acre-feet during the 2025 irrigation season.
In an order signed July 10 by IDWR Director Mathew Weaver, the methodology order outlines the anticipated supply and demand conditions that could impact surface water users with senior water rights on the Snake River
Under Idaho’s long-standing “first in time, first in right” water law, surface water users with senior rights—such as the Twin Falls Canal Co.—have legal priority over junior groundwater users. IDWR manages these water resources conjunctively, treating surface and groundwater as a connected system. The shortfall estimate, which increased from 63,000 acre-feet (an acre-foot is 325,851 gallons) in April, is based on the latest hydrologic conditions, including warm spring temperatures and rapid snowmelt, as well as updated modeling data.
Weaver’s order states, “On or before July 25, 2025, ground water users holding consumptive water rights bearing priority dates junior to October 11, 1900, within the Eastern Snake Plain Aquifer area of common ground water supply shall establish, to the satisfaction of the Director, that they can mitigate for their proportionate share of the predicted IDS (injury determination shortfall) of 75,300 acre-feet in accordance with an approved mitigation plan.”
If junior users cannot demonstrate they are mitigating their share of the shortfall, IDWR will issue an order curtailing their water use. However, most junior water users are unlikely to face curtailment thanks to the 2024 Water Settlement, negotiated last year by farmers and irrigation leaders.
“Idaho law and the constitution remain clear about first in time, first in right,” said IDWR Deputy Director Brian Patton. “However, regardless of these facts, most water users will not face curtailment thanks to the hard work farmers put in last summer to create the 2024 Water Settlement. Compromises like this, and investments in our water supply, will benefit Idaho water users into the future and I applaud their foresight.”
All junior groundwater users currently participating in an approved mitigation plan, including the 2024 Water Settlement, will avoid curtailment, officials said. Those who are not yet part of such a plan have until July 25 to comply. Participation in an approved plan is the only way for junior users to avoid having their water shut off to make up the shortfall owed to senior users.
While the Twin Falls Canal Co. may be impacted, the April Methodology Order did not find any shortfalls for the six other members of the Surface Water Coalition: A&B Irrigation District, Burley Irrigation District, Milner Irrigation District, Minidoka Irrigation District, North Side Canal Company and American Falls Reservoir District No. 2.
As irrigation season approaches, IDWR officials continue to encourage junior users to join an approved mitigation plan to maintain access to water during what is expected to be another dry year. — Charles Wallace, WLJ contributing editor
