Some groundwater users in the Eastern Snake River Plain may see curtailments this irrigation season due to lower runoff.
Idaho Department of Water Resources Director Gary Spackman on April 30 issued an order predicting 40,500-acre-foot shortfall to senior surface water rights in the Eastern Snake Plain for the 2021 irrigation season.
The department will issue a subsequent order identifying which junior groundwater users are subject to curtailment.
Idaho has prioritized replenishing the Eastern Snake Plain Aquifer for more than a decade. Some recovery has occurred due to state-sponsored and private recharge, and by groundwater users reducing demand. But senior right holders often still experience shortfalls because the aquifer needs further replenishment.
Spackman at the start of each season issues an order determining any shortfall to senior surface water right holders and obligations of junior groundwater pumpers to curtail usage or mitigate for depletions. The order reflects snowpack, runoff, reservoir carryover storage and aquifer condition.
Water managers predict 2.6 million acre-feet of runoff through July at the Heise gauge on the Upper Snake River, 80% of normal. Certain groundwater users may be subject to curtailment this irrigation season if they are not participants in, or in compliance with, an approved mitigation plan with a groundwater district, IDWR said in a release.
The established ESPA surface-water delivery call is the subject of a 2016 settlement agreement between groundwater users and a coalition of surface-water users. It protects groundwater users from curtailment and litigation if they are tied to a groundwater district or municipal mitigation plan.
Groundwater districts each year supply water to the coalition and reduce their own consumption under terms of the settlement, Idaho Ground Water Appropriators Executive Director Lynn Tominaga said in an interview. The settlement provides safe-harbor protection to participating groundwater or irrigation districts that are in compliance and good standing.
“By law, we have to keep people with senior water rights whole,” Deputy Director Matthew Weaver said. “We want to make the junior groundwater pumpers aware that despite the settlement agreements between the Surface Water Coalition, IGWA and the participating cities, if junior groundwater pumpers are not participating in an approved mitigation plan such as IGWA’s or the participating cities’ they could be subject to curtailment this year.”
Tominaga said 95-98% of groundwater users belong to a groundwater district or are protected under a city mitigation plan. Users that do not belong face curtailment risk — the extent of which depends on water conditions, demand and an IDWR reassessment each August.