BOISE - If you pump irrigation water in Eastern Idaho, a great water year is not a sure-fire guarantee of water.
This past week the Idaho Department of Water Resources issued a curtailment order predicting a 15,850 acre-foot irrigation shortfall to water users with senior priority surface water rights in the Eastern Snake River Plain Aquifer for this summer.
This predicted shortfall means that some groundwater users face curtailment during the irrigation season if they’re not participating in – or are not in compliance with – an approved mitigation plan. At least 85 water users may face curtailment.
The IDWR curtailment order says that junior groundwater users with priority date back to April 12, 1994, could face curtailment of water, and enlargement water rights with priority dates of March 14, 1971, are subject to a curtailment in the ESPA region if they’re not already participating in an approved mitigation plan.
Right now there are six approved mitigation plans for the ESPA surface water delivery call. These plans benefit members of the Idaho Ground Water Appropriators, A&B Irrigation District, Southwest and Goose Creek Irrigation Districts, and certain participating cities.
"By law, we have to keep people with senior water rights whole, and we need to notify affected junior groundwater pumpers that despite the recent historic settlement agreements between the Surface Water Coalition, IGWA, and the Participating Cities, if an affected junior groundwater pumper is not already participating in an approved mitigation plan they will be curtailed this year," said Mathew Weaver, Deputy Director of IDWR.
A lot of water litigation has resulted over conflicts between Snake River surface water users who have senior water rights under Idaho water law — first in time, first in right — and groundwater users with junior water rights in the ESPA. Under the law the Director of IDWR is required to issue an order at the beginning of the irrigation season, determining any shortfall in the water supply to the senior surface water right holders, and determining the obligations of junior groundwater pumpers to curtail water use or mitigate for depletions to water users with senior priority water rights.
Water conflicts have become commonplace because water levels in the ESPA have declined since the 1950s. Declining aquifer levels have affected spring flows and surface water flows in the Snake River, particularly in the Blackfoot to Milner reach of the Snake River and the Thousand Springs region near Hagerman.
Groundwater levels have improved because of state-sponsored aquifer recharge, groundwater pumping reductions, and ample water years, but aquifer water levels have not yet recovered to necessary levels to maintain recovery. Because of this, IDWR still predicts shortfalls to the senior surface water right holders even in record years like this, when federal storage reservoir operators forecast near-normal runoff and full reservoir supplies.
The April 1 joint forecast prepared by the United States Bureau of Reclamation and the United States Army Corps of Engineers predicted 3.2 million acre-feet of runoff from April to July at the Heise gauge of the Snake River, which is 99 percent of normal.
The mitigation plans of IGWA and the Participating Cities allows participating groundwater users to avoid curtailment this year and in the future, as well as avoid future litigation issues related to water use in the ESPA area that could affect cities, commerce, industry, agriculture, and the Southern Idaho economy.