IWRB Busy
Idaho Water Resource Board approves three major projects to improve water management of the Snake River and Eastern Snake Plain Aquifer.
The Idaho Water Resource Board (IWRB) voted to approve four major projects and initiatives while also touring a Twin Falls Canal Co. future project and receiving an update on water levels in the Eastern Snake Plain Aquifer (ESPA) during a busy three days of meetings here in Twin Falls.
The IWRB approved:
15 Groundwater to Surface Water Conversion Grants at a cost of $18.6 million in the second round of funding for those projects, which will reduce groundwater withdrawals from the ESPA. See spreadsheet on page three for the entities that received funding.
Approximately $9.1 million in additional funds for the Ridenbaugh Canal Diversion Modernization Project for the Nampa & Meridian Irrigation District on the Boise River and $1.5 million for a design-engineering study to repair the Milner Dam emergency spillway. Both of those projects have been added to the Board’s high-priority Regional Water Sustainability Projects list.
A three-year water quality study on the impact of IWRB recharge activities on the ESPA, to be performed by the U.S. Geological Survey, at a cost of $311,900. In addition, IWRB staff have created a new web portal that provides detailed public information about water quality monitoring reports related to the ESPA recharge sites. Go here to access that information.
Moving forward with a request to begin an Upper Snake River Basin WaterSmart Study, partnering with the Bureau of Reclamation, to evaluate the potential for adding water- storage capacity to existing Upper Snake River reservoirs and detail future water demand in the region. The Board will write a letter to Reclamation indicating their interest in partnering on the study to kick off the process. Officials with the Minidoka Irrigation District testified before the board, indicating their strong support for the study along with more than 15 letters of support from water users and conservation groups.
The IWRB’s funding and water-management initiatives in the Eastern Snake Plain region are directly related to assisting Groundwater Districts and the Surface Water Coalition in fulfilling the terms of the 2024 Water Settlement Agreement. The IWRB received $30 million in new funding from the 2025 Idaho Legislature to assist water users across the ESPA region with implementing aquifer-recharge, water conservation, real-time water measurement automation projects, and groundwater-to-surface water conversion projects.
In other action, the IWRB received an annual status report on ESPA water levels from IDWR hydrogeologist Mike McVay. He reported that there was “no change” in ESPA storage from the spring of 2024 to spring of 2025. Over the last 10 years, McVay said the water volume in the ESPA has had a net positive change of approximately 500,000 acre-feet.
IDWR hydrologists also reported that spring flows in the Thousand Springs reach of the Snake River and in the “Reach Gains” between Blackfoot and Minidoka have increased in the last several years as a result of IWRB ESPA recharge activities and ESPA groundwater districts’ reduced pumping activities.
The takeaways from the hydrologists’ report, looking at aquifer management activities from 2015- 2025, were as follows:
A net increase of 2.73 million acre-feet into the ESPA from a combination of IWRB recharge activities and pumping reductions by groundwater districts in the region.
IWRB recharge activities add 79,000 acre-feet of water into the “Reach Gains” during the irrigation season and 55,000 acre-feet during the winter.
The 5-year average of all mitigation activities has caused a net increase of 550,000 acre- feet of water into the ESPA. The hydrologists note that despite the IWRB’s recharge program and the groundwater districts’ pumping reductions, the ESPA is always “leaking” or discharging water out of the Reach Gains and Thousand Springs. So the net gains can be fleeting. It takes a consistent aquifer-enhancement program to see net gains to the ESPA water volume over time, officials said. On Thursday afternoon, the IWRB toured a number of sites where the Twin Falls Canal Co. plans to line the main canal. The Twin Falls Canal (TFCC) operational efficiency project would line 9.25 miles of leaky canal sections to save an estimated 19,000-68,000 acre-feet of water. The $26.3M project is estimated to take 5-8 years to complete with IWRB funding provided over a span of eight years.
