Water Shortfall

Water Shortfall

David Sparks Ph.D.
David Sparks Ph.D.
The Director of the Idaho Department of Water Resources has issued an updated mid-season methodology order for Snake River groundwater users, predicting a 170,500 acre-foot shortfall to senior priority surface water users in the Eastern Snake River Plain region in the 2021 irrigation season.

The shortfall prediction means that IDWR will curtail more than 500 groundwater rights with priority dates junior to June 14, 1977, in the coming weeks if the holders of those water rights do not come into compliance with an approved mitigation plan with a groundwater district.

Currently, there are at least four approved mitigation plans for the ESPA surface water delivery call. These plans benefit members of the Idaho Ground Water Appropriators, Inc. (IGWA), A&B Irrigation District, Southwest and Goose Creek Irrigation Districts, and certain cities referred to as the "Participating Cities."

The Director’s updated order was issued on July 20, 2021, and updated the Department’s previous April injury determination. The Department’s injury determination has significantly increased since its initial determination in April largely as a result of the historic drought affecting Idaho. Junior water users who could be affected by the order were sent a copy of the order this week.

"By law, we have to keep people with senior water rights whole, and we want to make the junior groundwater pumpers aware that despite the settlement agreements between the Surface Water Coalition (“SWC”), 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’ approved mitigation plans, they could be subject to curtailment this year," said Mathew Weaver, Deputy Director of IDWR.

Much water litigation has resulted in conflicts between Snake River surface water users who have senior water rights under the basic principle of Idaho water law — first in time, first in right — and groundwater users with junior water rights in the ESPA. Consequently, the Director of IDWR is required

to issue an order at the beginning of the irrigation season, and then again in early July, 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 the holders of senior priority water rights.

In April 2021, the Director’s order identified a shortfall of 40,500 acre-feet of water to the SWC. The number ballooned to 170,000 acre-feet after a very dry spring and summer. Two members of the SWC, Twin Falls Canal Company and American Falls Reservoir District #2, were found to be injured by junior groundwater pumping, according to the order.

The increased injury comes in response to significant drought conditions resulting from above average temperature and far below-average precipitation. Data measured at the Natural Resources Conservation Service's SNOTEL sites in the Upper Snake River Basin showed the basin received 49 percent, 121 percent, and 13 percent of average precipitation in April, May, and June, respectively, according to the Director’s updated order. The National Weather Service's Twin Falls weather station reported 29 percent, 51 percent, and 2 percent of normal precipitation in April, May, and June. Twin Falls temperatures were 0.3 degrees below normal for April, 0.1 degrees above normal for May, and 8.4 degrees above normal for June. 1

The mitigation plans of IGWA and the Participating Cities allow participating groundwater users to avoid curtailment this year and in the future, as well as avoid future large-scale litigation issues related to water use in the ESPA area that could affect cities, commerce, industry, agriculture, and the Southern Idaho economy, officials said.

If junior groundwater users do not join a groundwater mitigation plan or demonstrate to the Director how their water use will not cause injury to senior surface water users in the next 14 days, their water rights will be curtailed, the order said.

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