IDWR water rights
IDWR agents work to bring all 743 water users into compliance with July Methodology Order; existing curtailment, mitigation activities expected to cover shortfall identified in September order
In the ongoing Surface Water Coalition’s conjunctive administration delivery call, Director Mathew Weaver of the Idaho Department of Water Resources (IDWR) has completed Steps 7 and 8 in a Sept. 11, 2025 Methodology Order, as required by the court.
After a dry summer with below-normal precipitation, the Director calculated a combined total shortfall of 63,700 acre-foot split between the Twin Falls Canal Co. (59,600 acre-feet) and the American Falls Reservoir District #2 (4,100 acre-feet) for the remainder of the irrigation season.
The Director also found that the curtailment actions required under the May and July curtailment orders will produce 58,000 acre-feet of water for Twin Falls Canal Co. and AFRD2 in the Blackfoot to Minidoka “Reach Gains,” this year, leaving a shortfall of approximately 5,000 acre-feet. As a result of this order’s injury determinations, there is no change to the curtailment status of affected water rights.
“The predicted mid-August through September benefits to the near Blackfoot to Minidoka reach from curtailment of ground water rights bearing priority dates junior to August 28, 1955, through the end of July followed by curtailment of groundwater rights junior to October 11, 1900, are less than the August IDS (in- season demand shortfall) of 63,700 acre-feet,” the order said. “Continuing the curtailment of ground water rights junior to October 11, 1900, will offset as much of the August IDS as possible.”
Enforcement Activities/Water User Outreach
Meanwhile, since the Director’s issuance of the May Curtailment Order, Water District and Department staff members have been working to enforce the curtailment orders. These efforts ramped up following the issuance of the July Curtailment order. As many as 15 IDWR staff members have been in the field coordinating with the holders of the 743 affected junior groundwater rights to ensure they come into compliance by joining a groundwater district’s approved mitigation plan or shutting off their water.
IDWR publishes a weekly summary of enforcement activities on its IDWR website. As of Sept. 11, enforcement activities have produced the following results:
Out of the 743 groundwater rights subject to curtailment by the Director’s July order, 469 of those uses have been resolved because the user joined an approved mitigation plan, curtailed their use, or limited their use to comply with domestic exempt volumes.
Out of the 469 resolved cases, 158 groundwater users have joined an IDWR-approved groundwater district mitigation plan and have received safe harbor. Several additional water users have informed their water district watermasters that they are in the process of joining a ground water district for mitigation purposes. Several cities are also in the process of joining the Coalition of Cities mitigation
plan. IDWR is following up with those water users to ensure all necessary steps have been taken. Water users who don’t make good on their commitments to join a mitigation plan may face future civil penalties.
204 junior groundwater users stopped using ground water to come into compliance with the July order. Water District and IDWR staff members are inspecting these self-curtailed acres every two weeks to ensure ongoing curtailment.
In the other resolved cases, the groundwater users were small domestic water users whose water use is covered by the domestic exemption.
IDWR also has been working to reach 70 water users who were difficult to reach due to the lack of a valid or working address or phone number. All but one of the 70 water users have been contacted now, and of those cases, 48 have been resolved, and 22 require additional information.
So far, IDWR has issued Notices of Violation to three water users who were found to be in violation of the July order and is pursuing a compliance conference to establish and collect civil penalties, which are assessed at $300 per illegally irrigated acre. Delivery Call Background The Methodology Order is the court-approved process IDWR uses to evaluate water supply conditions and irrigation demand in the delivery call proceedings. From that data, IDWR calculates an in-season demand shortfall, which quantifies the impacts or injury to Snake River surface water users with senior water rights caused by junior water users pumping from the Eastern Snake Plain Aquifer (ESPA). Under Idaho water law, surface water users with senior water rights have priority over water users with junior surface rights on the Snake River and the ground water rights from the ESPA. The rule of law is “first in time, first in right.” On the Eastern Snake Plain, IDWR manages both surface and groundwater resources together as one whole, or “conjunctively,” in calculating impacts each year. Most junior water users in good standing who are participating in an approved mitigation plan, including the 2024 Water Settlement, will avoid curtailment as a result of the September Methodology Order, officials said. Any junior water users who are not participating in an approved mitigation plan need to join one to avoid curtailment, officials said. Much water litigation has resulted from conflicts between Snake River surface water users with senior water rights and groundwater users with junior water rights in the ESPA. The litigation led to a water delivery call in 2005 by the SWC, the coalition of seven surface water irrigation entities with senior water rights in Southern Idaho. Under the SWC's water delivery call in 2005, the Director of IDWR is required by law to issue an order at the beginning of the irrigation season and again in early July determining the shortfall to senior surface water users due to the pumping impacts of junior groundwater users and determining their obligations to curtail water use or mitigate for depletions to the holders of senior priority water rights. Please see the Director’s September Methodology Order for more details.
