Idaho adopts 2024 mitigation plan for Eastern Snake Plain; director keeps enforcement tools while pausing groundwater management plan

Idaho Department of Water Resources Director Matthew Weaver told the House Resources Committee that the parties to the long‑running Eastern Snake Plain delivery call reached a settlement in November 2024 that he adopted as a mitigation plan on Jan. 3, 2025. The plan, Weaver said, requires pumping reductions and recharge, establishes a four‑year averaging allotment for junior groundwater users and clarifies that only users who fail to meet their proportional obligations will be individually curtailed.

Weaver said the plan “continues to require the physical acts of pumping reductions and recharge” and that it “builds a 4 year pumping allotment that is effectively, a practice that allows the groundwater users to average their consumption over 4 years.” He told committee members he supported the agreement and had adopted it as a mitigation plan but that a limited reconsideration request was pending about whether reporting should be on a calendar year or a water year.

Why it matters: the Eastern Snake Plain adjudication and delivery call have produced decades of contested proceedings and court rulings that set how Idaho conjunctively manages surface water and groundwater. Weaver told lawmakers the 2024 mitigation plan “holds the potential to improve water levels in the ESP and enhance reach gains to the Snake River” and provides a specific path for tributary groundwater basins and their users to join the mitigation regime and be protected from curtailment.

Most important facts first: Weaver said the new settlement requires in‑season measurement and reporting of groundwater diversions so exceedances are known in near‑real time rather than months later. The plan also defines standards for qualifying recharge activities and includes mechanisms for additional junior users from tributary basins to contribute proportionally to mitigation (pumping reductions, recharge, or purchase of storage water) to gain protection from curtailment.

Weaver summarized the department’s enforcement posture and recent litigation. He said a federal challenge to the department’s use of Idaho Code sections addressing show‑cause procedures for forfeiture (cited in testimony as Idaho Code 42‑222 and 42‑224) concluded in federal court last fall with a ruling that, as applied, those statutes are constitutional on the federal government’s primary claims; other statutes named in the suit were found to raise supremacy‑clause issues. Weaver said, contingent on any appeals, the department will move four existing show‑cause orders to hearing and expects to issue decisions in the coming one to two years.

On curtailment and timing, Weaver reviewed 2024 events: in April 2024 the department made an injury determination that junior groundwater users were injuring senior surface‑water rights; after conditional compliance by juniors the director issued a curtailment order in late May 2024. Field curtailment lasted about a week and the parties negotiated a temporary settlement to stay curtailment through the irrigation season; they finalized the November 2024 settlement and Weaver later adopted it as a mitigation plan.

Weaver described the settlement’s mechanics: a four‑year averaging block for junior users, clear standards for qualifying recharge activity, in‑season measurement and reporting, and language intended to limit curtailment to noncompliant individual users rather than automatically curtailing whole groundwater districts when a subset of members fails to comply.

Data and modeling: Weaver and the board’s modelers found that from 2016–2023 the combined state‑sponsored managed recharge (about 268,000 acre‑feet average) and private pumping reductions/private recharge (about 341,000 acre‑feet average) yielded roughly 600,000 acre‑feet of average annual augmentation. Department modeling showed that combined actions since 2016 have “changed the trend” of decline in the aquifer, although Weaver cautioned that incidental recharge from older irrigation practices continues to decline as efficiency projects reduce seepage.

Next steps and department actions: Weaver said the department will pause active development of a formal Eastern Snake Plain groundwater management plan to allow parties to implement and evaluate the 2024 mitigation plan’s effects, but the agency will take specific steps to support the mitigation plan and possible future management plans. Those actions include issuing water‑master instructions, publishing a groundwater management water budget and an index metric for the ESPA, creating or modifying water districts in tributary basins, and expediting project review for recharge and related infrastructure.

Scope and uncertainty: Weaver warned that if federal or state court orders require the department to move forward with deferred domestic and stock water claims in the Snake River Basin adjudication, the department could face a large, multiyear workload (Weaver estimated “tens of thousands, if not in excess of a hundred thousand” claims) and said the agency currently lacks dedicated staff for such an effort.

Weaver closed by urging continued monitoring and collection of data and said he hoped the settlement proves durable and effective. He invited questions from committee members.

Ending: Committee members asked about targets for recovery, incidental‑recharge losses from efficiency projects, and what the mitigation plan would mean for individual irrigators; Weaver said the plan’s averaging and the ability to join it provide protection for many junior users but reiterated that stabilization or recovery of the aquifer will require substantive, long‑term commitments to recharge and reduced pumping.