BOISE, Idaho (IDWR News Release) – In the ongoing Surface Water Coalition’s conjunctive administration delivery call, Idaho Department of Water Resources Director Mathew Weaver issued a final curtailment order today, finding that six groundwater districts were deficient in complying with their existing, approved mitigation plans to address an injury volume of 74,100 acre-feet to senior water users.
The order indicates that water rights junior to March 31, 1954, in those six districts are now subject to curtailment. The order directs watermasters to begin the curtailment process. Groundwater users who have not previously participated in a groundwater district for mitigation purposes have an additional 15 days to join an approved mitigation plan or face curtailment.
The order is expected to affect approximately 6,400 groundwater rights overlying the Eastern Snake Plain Aquifer (ESPA) region. Please see Attachments A and B to the Director’s order for the entities that will be impacted by the order.
Not all junior groundwater users are failing to comply with their approved mitigation plans. In his order, Weaver found that six entities, the Southwest Irrigation District, Coalition of Cities, Water Mitigation Coalition, and the American Falls-Aberdeen, Henrys Fork and Madison ground water districts continue to comply with approved mitigation plans and consequently are protected from curtailment.
The six groundwater districts found to be in noncompliance with an approved mitigation plan are:
• Bingham Ground Water District
• Bonneville-Jefferson Ground Water District
• Jefferson-Clark Ground Water District
• Magic Valley Ground Water District
• Carey Valley Ground Water District
• North Snake Ground Water District
The Director’s curtailment order, and other related orders from the past few weeks, clearly set forth the requirements for the GWDs to comply with either of their two existing approved mitigation plans and thus avoid curtailment. Because of ongoing disagreement with the Department and amongst themselves, the groundwater districts facing curtailment ultimately chose not to comply with either of their plans in the manner required. As a result, many junior groundwater users will be curtailed who might otherwise have been spared.
“It is surprising to us that six groundwater districts would choose not to live by the terms of either of their approved mitigation plans and subject their members to curtailment ,” said Brian Patton, Deputy Director of IDWR.
ESPA groundwater users have had ample notice that they needed to take action to avoid curtailment.
On April 18, 2024, Weaver issued the April As-Applied Methodology Order for the 2024 irrigation season, affecting junior groundwater users in the ESPA region. The April order determined a shortfall of 74,100 acre-feet of water to the Twin Falls Canal Co. (TFCC). TFCC has senior water rights dating to October 1900. The April Order gave junior groundwater users until May 2 to supply mitigation notices with the Department demonstrating their compliance with their approved mitigation plans.
The Methodology Order is the court-approved process IDWR uses to determine injury to senior water right holders caused by junior-priority water users pumping from the ESPA.
Under Idaho water law, water users with senior water rights have priority over water users with junior rights. On the Eastern Snake River Plain, IDWR administers both surface and groundwater resources together as one whole, or “conjunctively.” In general, groundwater rights are junior to surface water rights.
The 74,100 acre-foot shortfall is based on a number of factors including mountain snowpack, reservoir content, irrigation need, and aquifer conditions.
The Director of IDWR is required to issue an order at the beginning of the irrigation season, and then again in early July, determining any shortfall in water supply to the senior surface water right holders. When the Department calculates a shortfall, junior groundwater pumpers must mitigate their impacts or IDWR will curtail junior uses.
Please see the Director’s May 30 order for more details. As required by law, the Director will issue an updated order in July after considering the new water supply and crop water need information available at that time.
