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November 15, 2023  |  Written by Maximilian C. Bricker

An Update on Legal Matters Involving the Eastern Snake River Plain Aquifer

This alert provides a general overview of various pending matters that affect the interests of water users located within the boundaries of the Eastern Snake River Plain Aquifer (ESPA). All of the administrative matters described herein relate to the Idaho Department of Water Resources’ (IDWR) view that it must increasingly regulate existing junior ground water rights, and prevent new consumptive uses, to avoid injury to senior surface water rights due to perceived declines in the ESPA.

Future alerts will expand upon the individual matters in greater detail.

Background: the ESPA

The ESPA underlies an area of the Eastern Snake River Plain. The ESPA is hydraulically connected to surface water sources, including the Snake River. IDWR administers the surface water and ground water of the ESPA conjunctively. The water in the ESPA comes primarily from tributary basins, either ground water underflow from tributary aquifers or water in tributary streams that infiltrates directly through the streambed and into the ESPA or indirectly when it is used for irrigation. The ESPA discharges to the Snake River at several locations, notably springs in the American Falls reach above Milner Dam, and in the Thousand Springs reach below Milner Dam. A map of the ESPA, and a table of its annual flows, is below.

Source: Spronk Water Engineers, Inc.

Surface Water Coalition Delivery Call

In January 2005, a group of canal companies holding senior surface water rights, the Surface Water Coalition (SWC), placed a “delivery call” asking that IDWR curtail junior ground water pumping that was allegedly injuring its members’ water rights. In May 2005, the Director of IDWR issued an order finding injury to a limited extent and ordering ground water users to supply water to the SWC to replace depletions associated with their junior pumping. Before a hearing could be held in the matter, the SWC brought declaratory judgment seeking a ruling that their members were entitled to divert 100 percent of their decreed irrigation water rights and storage water rights every year. They lost at the district court and the Idaho Supreme Court ruled that SWC members could only call for the amount of their water rights that they could beneficially use, rather than the amount on the face of their decrees.

In 2010, after five years of litigation including a three-week hearing, IDWR issued its first “Methodology Order” describing the steps the agency would take to determine the annual extent of the SWC’s material injury: when water supply and climate conditions suggest that the SWC’s reasonable in-season irrigation demands and reasonable carryover storage amounts will not be satisfied, injurious junior pumping must be properly mitigated or face curtailment. Many junior ground water users, including a group of municipalities (Cities), have entered into an approved mitigation plan that insulates them from curtailment so long as they comply with the terms of the mitigation plan.

The Methodology Order has been updated on several occasions since it was originally issued, and in April 2023, then-Director Gary Spackman issued the Fifth Amended Methodology Order, which, among other things, changed the SWC’s baseline year demand from 3,194,722 acre-feet to 3,341,939 acre-feet, an increase of over 147,000 acre-feet, despite the fact that irrigation practices have gotten more efficient and many formerly-irrigated acres in the SWC members’ service areas have been “hardened”—i.e., had houses or strip malls built on them. A group of ground water districts (GWDs) and the Cities challenged several aspects of the order and participated in an evidentiary hearing in June 2023. IDWR rejected the Cities’ and GWD’s evidence in the July 19, 2023 Post-Hearing Order. The GWDs and Cities sought judicial review and these appeals are ongoing with oral argument expected in the district court in February of 2024.

ESPA Moratorium

In May 1992, IDWR issued an order establishing a moratorium on the approval of new applications to appropriate surface water or ground water in the Snake River Basin upstream from the U.S. Geological Survey gaging station on the Snake River at Weiser, Idaho. A map of the Snake River Basin Moratorium Area is below.

Source: Amended Snake River Basin Moratorium Order at p. 30 (2022).

In October 2022, IDWR issued an Amended Snake River Basin Moratorium Order, which, among other things, adopted a new policy that IDWR shall consider applications for municipal water use and for domestic use from community water systems to be fully consumptive, based on the potential under Idaho law that municipalities may fully consume their water rights under Idaho Code section 42-201(8). If the order stands, municipalities that appropriate new water rights will be required to mitigate 100 percent of the water diverted—an extremely steep cost that is likely to impact economic development in eastern Idaho—while all other water users need only mitigate for the amounts of water consumed. The Cities and other municipal water providers challenged this portion of the order at an evidentiary hearing in October before Director Mathew Weaver. The Director is expected to issue a final post-hearing order sometime in early 2024.

ESPA Ground Water Management Area

In November 2016, IDWR issued an Order Designating the Eastern Snake Plain Aquifer Groundwater Management Area. Idaho Code section 42-233b authorizes the Director to do so when the Director determines a ground water basin “may be approaching the conditions of a critical ground water area.” IDWR has since issued orders affirming the designation order despite factual and legal challenges brought by various water users. A map of the ESPA Groundwater Management Area (GWMA) boundary is below.

Source: Order Designating the Eastern Snake Plain Aquifer Groundwater Management Area at p. 26 (2016).

The designation order states that one of IDWR’s objectives is to arrest and reverse chronic declines in ESPA storage and spring discharges. One tool available to IDWR to meet this objective is to approve a “groundwater management plan” (management plan) that “would provide the framework for managing ground water in the areas within the [ESPA] to ensure a reasonably safe supply of ground water for irrigation of cultivated lands or other uses in the basin.”

In the summer of 2023, IDWR formed an ESPA GWMA Advisory Committee, comprised of representatives from various water user groups, to prepare a draft management plan. The initial Advisory Committee meeting took place in September 2023 and meetings have been occurring monthly since. The Advisory Committee is presently discussing the overarching goals and objectives of the management plan.

IDWR has determined that a management plan is necessary, notwithstanding the ongoing SWC Delivery Call, because it asserts that conjunctive administration alone is an inefficient or ineffective means of addressing the underlying ESPA supply issues.

It is uncertain how the management plan will ultimately take shape, e.g., whether it will require groundwater users to incur additional obligations, to curb declines in ESPA storage and spring discharges, beyond those set forth in existing mitigation plans. What is more certain is that legal disputes on the management and administration of the ESPA are not going away soon.

For more information or with questions, please contact:

Disclaimer: Somach Simmons & Dunn represents the interests of the City of Pocatello in legal matters including, but not limited to, those described herein.

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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