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June 4, 2024  |  Written by Maximilian C. Bricker

IDWR Issues Unprecedented Order Curtailing Widespread ESPA Ground Water Users

On May 30, 2024, the Director of the Idaho Department of Water Resources (IDWR) issued a Final Order Curtailing Ground Water Rights Junior to March 31, 1954 (Curtailment Order) as part of his administration of the ongoing Surface Water Coalition (SWC) delivery call. While not the first of its kind, this Curtailment Order is significantly more wide-reaching and controversial than any prior order, primarily due to two recent developments: (1) the Director’s switch from using “steady-state” to “transient” modeling to determine curtailment dates; and (2) several Ground Water Districts’ (Districts) refusals to comply with a 2016 Mitigation Plan that otherwise protects the farmer-patrons of those Districts from curtailment.


The Director issued the Curtailment Order in response to an ongoing delivery call filed by the SWC, a group of irrigators with senior surface water rights in Idaho’s Magic Valley. In 2005, the SWC asked IDWR to curtail all ground water pumping from the Eastern Snake Plain Aquifer (ESPA), alleging that the pumping was injuring their senior surface water rights. IDWR denied the request to curtail all ESPA ground water users, but over a period of several years (and several trips to the Idaho Supreme Court), IDWR incorporated some of the principles of its Rules for Conjunctive Management of Surface and Ground Water Resources (CMR) to develop a “Methodology” to administer the SWC call each year.

IDWR has periodically amended the Methodology Order, issued in 2010, with new data and new procedures, most recently in 2023, when IDWR adopted the use of “transient” modeling to determine curtailment dates, with the reasoning that a transient analysis better redresses the SWC’s injury within that irrigation season. Practically speaking, using transient modeling yields a more senior curtailment date than steady-state modeling to offset the same amount of injury, thereby affecting a larger pool of ESPA ground water users.

In 2009, IDWR approved the Districts’ (under the auspices of an umbrella organization, Idaho Ground Water Appropriators, Inc. (IGWA)) mitigation plan submitted under CMR Rule 43. Under this plan (the 2009 Mitigation Plan), the Districts could continue to pump without fear of curtailment so long as they satisfied the terms of the plan (namely, delivering storage water to the SWC at times and in amounts set forth by the Methodology Order).

In 2016, following a global settlement in the SWC delivery call matter (the 2015 Settlement Agreement), IGWA sought approval of a new mitigation plan (the 2016 Mitigation Plan). IDWR approved this plan, which notably called for changes in irrigation practices by the Districts’ patrons with an eye towards enhancing the ESPA rather than redressing the SWC’s injury per se.

Map showing the locations and boundaries of the SWC Members and IGWA Members.

The Director determined that several Districts violated their obligations to conserve ground water under the 2016 Mitigation Plan in 2021 and 2022. The offending Districts dispute their breaches, and in many instances also dispute the Director’s interpretation of the 2016 Mitigation Plan. Consequently, implementation of the plan has, for several Districts, become a political issue as much as a water rights issue, and six of the nine Districts subject to the 2016 Mitigation Plan have refused to accept and abide by its terms as interpreted by the Director.

2024 Developments

The Curtailment Order arises directly from IDWR’s April 18, 2024 Final Order Regarding April 2024 Forecast Supply (Methodology Steps 1–3), predicting a shortfall of 74,100 acre-feet to Twin Falls Canal Company (an SWC member) this irrigation season. The Methodology Steps 1-3 order employed transient modeling to establish a curtailment date of March 31, 1954, meaning all ESPA ground water users junior to that date (collectively, over 600,000 acres worth of irrigated lands) and not operating under an approved mitigation plan are subject to curtailment. By contrast, steady-state modeling would have yielded a curtailment date in the late-1980’s and would have subjected less than 100,000 acres of irrigated lands to curtailment.

Graph comparing the effects of using “steady-state” versus “transient” modeling to determine curtailment dates.

In response to the Director’s Methodology Steps 1-3 Order, the Districts registered their intentions to operate under either the 2009 Mitigation Plan or the 2016 Mitigation Plan. This split was driven in part by the fact that protection from curtailment is only available if an entity can show that it intends to operate under an approved mitigation plan and that it is in compliance with the plan. At least three of the Districts are in breach of the 2016 Mitigation Plan and thus looked to the 2009 Mitigation Plan as a means to avoid curtailment. However, the validity of the 2009 Mitigation Plan is in serious question due to a March 2024 order by an IDWR-appointed Hearing Officer concluding that the 2016 Mitigation Plan superseded the 2009 Mitigation Plan.

Although the Director has not yet adopted the Hearing Officer’s order, he issued an order on May 28, 2024, determining that the Districts could not obtain protection under the 2009 Mitigation Plan in 2024, yet still offered them protection from curtailment if they notified him by 5:00 p.m. on May 29, 2024, that they would comply with the 2016 Mitigation Plan. Six of the nine Districts rejected this offer, and the Director issued the Curtailment Order the next day, directing watermasters through the ESPA to begin shutting off wells with priority dates junior to March 31, 1954.

American Falls-Aberdeen, Madison, and Henry’s Fork are the only three Districts that agreed to operate under the 2016 Mitigation Plan in 2024, thus their constituents are not subject to the Curtailment Order. Additionally, other ground water users that are not members of IGWA and are in compliance with their approved mitigation plans—many municipalities across the ESPA, for example—are also not subject to the Curtailment Order.


While prior IDWR orders curtailed ESPA ground water users with wells having priority dates as senior as 1971, never before has IDWR curtailed users with priority dates in the 1950’s or 1960’s, and never before has this scale of irrigated lands not been protected from curtailment through their Districts’ mitigation plans.

Various ongoing matters before both IDWR and Idaho courts involve questions about the enforceability of the 2015 Settlement Agreement and corresponding 2016 Mitigation Plan. For the time being, however, the six Districts’ blatant defiance of IDWR’s orders has led to serious consequences for their patrons.

For more information or with questions, please contact:

Somach Simmons & Dunn represents the City of Pocatello and American Falls-Aberdeen Ground Water District in legal matters including, but not limited to, those described herein. This alert reflects the observations of the authors and is not intended to limit or otherwise describe the views of our clients. Somach Simmons & Dunn provides the information in its Environmental Law & Policy Alerts and on its website for informational purposes only.  This general information is not a substitute for legal advice, and users should consult with legal counsel for specific advice.  In addition, using this information or sending electronic mail to Somach Simmons & Dunn or its attorneys does not create an attorney-client relationship with Somach Simmons & Dunn.

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