Updated curtailment order
IDWR issues updated curtailment order for junior groundwater users, requiring them to join a mitigation plan or face curtailment; water users who joined mitigation plans are protected from the order
IDWR Director Mathew Weaver issued an updated curtailment order today for groundwater users who draw water from the Eastern Snake Plain Aquifer and whose water rights are junior to Oct. 11, 1900. This order updates the Director’s previous injury determination and curtailment order issued in May. Junior groundwater users who were informed on May 16 of the pending curtailment order have an immediate requirement to join a mitigation plan, the order says, while newly curtailed groundwater users effected by the July Curtailment Order, will have a 15-day grace period to join a mitigation plan.
Five groups of groundwater users are protected from curtailment, the order says, because they are operating under IDWR-approved mitigation plans. These groups are:
The Southwest Irrigation District.
Coalition of Cities.
A&B Irrigation District
Water Mitigation Coalition
Groundwater Districts. The members of the Groundwater Districts are protected under a stipulated mitigation plan approved following completion of the 2024 Water Settlement Agreement. Groundwater users who are subject to this curtailment order are encouraged to join their local ground water district as soon as possible in order to avoid curtailment. In an order on July 10, in the ongoing Surface Water Coalition’s conjunctive administration delivery call, Director Weaver found that the Twin Falls Canal Co. may face a shortfall of 75,300 acre-feet of water in the 2025 irrigation season. 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 groundwater 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 rights on the Snake River and the ESPA. The rule of law is “first in time, first in right.” On the Snake River, IDWR manages both surface and groundwater resources together as one whole, or “conjunctively,” in calculating impacts each year. IDWR Deputy Director Brian Patton said it’s important for IDWR to be consistent in its enforcement of the Methodology Order since most junior groundwater users are protected under existing mitigation plans, and their support for those plans will hinge on IDWR’s enforcement efforts to ensure all groundwater users are complying with the order.
IDWR officials are working in cooperation with local water districts. They are meeting with junior groundwater users to ensure they are aware of the curtailment orders and how they can come into compliance with them, Patton said. With the new July Curtailment Order, the group of affected water users and water rights has grown by several hundred. Because of the early curtailment date of Oct. 11, 1900, many effected water users may not have previously faced curtailment and not been aware of the ongoing delivery call process. Agents in the field are confirming compliance with the curtailment orders and helping water users understand the matter and identify their options.
Why Has the Injury Volume Increased Since April?
The 75,300 acre-foot shortfall estimate is based on observed supply and demand conditions from April through June, along with projections for the remainder of the irrigation season. A drier and warmer-than-normal spring with rapid snowmelt and reduced runoff led injury estimates to increase from 63,000 acre-feet in the April forecast and Methodology Order. According to the June Joint Forecast issued by the U.S. Bureau of Reclamation and the U.S. Army Corps of Engineers, the unregulated flow at the Heise gage for the June-July period is projected at 1,350,000 acre-feet - approximately 75% of normal. This represents a decline from the April forecast, which had estimated flows for the April-June period of 102% of normal.
Delivery Call Background
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.
