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2024 Surface Water Coalition Delivery Call

In 2005, a group of canal companies and irrigation districts that diverted and delivered water from the Snake River to approximately 550,000 acres of farmland formed the Surface Water Coalition (SWC). Once formed,  the SWC filed a delivery call against junior ground water users claiming that junior ground water pumping was depleting the Eastern Snake Plain Aquifer (ESPA) and the hydrologically connected Snake River. The Idaho Ground Water Appropriators (IGWA) and member ground water districts formed in response to the SWC delivery call to respond on behalf of junior ground water users collectively irrigating almost 1,000,000 acres of farmland. Through the delivery call proceeding, it was determined that depending on surface water supply, ESPA, and crop need conditions, the depletion effects from pumping the ESPA materially injure the SWC. A court-approved “Methodology” was implemented in 2010 that evaluated the water supply and crop need conditions each year and determined the magnitude of the injury. The Methodology has been implemented since 2010, and during that time, it has undergone six revisions, most recently in 2023. When the Methodology determines injury, junior ground water users found to be causing the injury must mitigate their injury under the authority of a State-approved mitigation plan or be curtailed.

On July 19, 2023, the Department issued its Sixth Final Order Regarding Methodology for Determining Material Injury to Reasonable In-Season Demand and Reasonable Carryover in the Surface Water Coalition Delivery Call (“Methodology Order”). The Methodology Order implements nine steps for determining material injury to members of the Surface Water Coalition (“SWC”). The Director is required by the Idaho Constitution, Idaho Law, and numerous court decisions to administer ground and surface water rights conjunctively, in response to the 2005 delivery call filed by the SWC.

On April 18, 2024 the Director used the Sixth Amended Methodology to determine groundwater pumping injured senior surface water rights by 74,100 acre-feet. A curtailment order is issued following the determination of predicted in-season demand shortfall in the April Forecast Supply (Methodology Steps 1-3) (“As-Applied Order“).

On May 30, 2024 the Director issued the Final Order Curtailing Ground Water Rights Junior to March 31, 1954. Junior groundwater users who cannot mitigate their proportionate share of the predicted in-season demand shortfall in accordance with an approved mitigation plan are curtailed.

The 2024 Legislature passed Senate Bill 1341, expanding the area of common ground water supply (ACGWS) for the Eastern Snake Plain Aquifer (ESPA). The ESPA ACGWS is the administrative boundary used by the Department to administer water rights regarding the Surface Water Coalition (SWC) Delivery Call. SB 1341 modifies the ACGWS to reflect the Eastern Snake Plain Aquifer Model boundary, v2.2.  When the new boundary goes into affect on July 1, 2024, approximately 1,400 new ground water rights will be brought into the delivery call proceeding. The Department sent notice to the holders of affected water rights in May and is currently considering the process to bring the new water rights into administration.  

Click on the links below for information and resources regarding the SWC Delivery Call and the 2024 Curtailment Order:

Methodology and Curtailment Orders:

IDWR Press Releases and FAQs:

Surface Water Coalition and Idaho Ground Water Appropriators, Inc.: 

Groundwater and Eastern Snake Plain Aquifer Information:

The map above illustrates the new boundaries of the Eastern Snake Plain Aquifer Area of Common Groundwater Supply, updated as per Senate Bill 1341. The updated boundary will go into effect on July 1, 2024. 

Click here for a pdf version of the updated ESPA ACGWS Map.

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