Idaho Department of Water Resources (IDWR) Director Mathew Weaver issued a final curtailment order on May 30 for junior water users in the Eastern Snake Plain Aquifer (ESPA).
The order was issued due to six groundwater districts failing to comply with their approved mitigation plans, Weaver said. These plans were meant to address an injury volume of 74,100 acre-feet to senior water users.
As a result, water rights junior to March 31, 1954, are now under the curtailment order, with watermasters instructed to initiate the process. The order is projected to affect approximately 6,400 groundwater rights in the ESPA.
Under Idaho water law, users with senior water rights have priority over those with junior rights. IDWR administers surface and groundwater resources conjunctively on the ESPA, treating them as a single integrated system. Generally, groundwater rights are considered junior to surface water rights.
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.
According to IDWR, ESPA groundwater users have had ample notice to take action to avoid curtailment.
“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.
On April 18, Weaver issued the April as-applied methodology order for the 2024 irrigation season, impacting junior groundwater users in the ESPA region. The order identified a shortfall of 74,100 acre-feet of water to the Twin Falls Canal Co. Junior groundwater users were given until May 2 to submit mitigation notices to IDWR, demonstrating their compliance with approved mitigation plans.
The April release stated the shortfall is based on the April 4 joint forecast of 3.37 million acre-feet of water flow at the Snake River Heise gage from April 1 through July 31. This forecast, calculated by the Bureau of Reclamation and the U.S. Army Corps of Engineers, considers mountain snowpack and predicted streamflow runoff, with the April forecasted flow volume equating to 102% of the average. Additionally, the shortfall determination takes into account current groundwater levels in the ESPA.
Despite intensive management efforts, groundwater levels measured in the spring of 2023 were at or near all-time lows dating back to the 1950s. These low groundwater levels in the ESPA impact spring flows and surface water flows in the Snake River.
Gov. Brad Little (R) issued a statement supporting the order and Weaver’s decision.
“If we continue the status quo with water use on the Eastern Snake Plain, we are setting our children and grandchildren up for failure,” Little said. “Water curtailment is never desired, but the director must follow Idaho law and the Constitution in issuing this order.”
Little said his administration has been working on water issues for years, most recently with the formation of a Groundwater Management Plan Advisory Council. In 2023, Little urged IDWR to form an advisory council composed of representatives from surface water users, groundwater irrigators, and municipalities to develop a groundwater management plan.
“Idahoans have always and will continue to solve our own problems, and we remain committed to working with all water users in Idaho to ensure we have a sustainable supply of water for this generation and future generations,” Little said.
According to the Idaho Capital Sun, the Idaho Groundwater Appropriators criticized the order, calling it the largest curtailment of water use in state history. The agency warned it could dry up approximately 500,000 acres of farmland, potentially resulting in the economic loss of millions of dollars.
“What remains is an utterly absurd situation, where hundreds of thousands of acres of farmland, and their associated economic benefits, are thrown away during a wet year to cause a small amount of additional water to overflow from the aquifer into the Snake River,” Idaho Groundwater Appropriators Attorney TJ Budge said.
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.
As required by law, Weaver will issue an updated order in July after evaluating the latest water supply and crop water need information available at that time. — Charles Wallace, WLJ contributing editor
