TWIN FALLS, Idaho—Idaho surface and groundwater irrigators have finalized terms of an agreement aiming to reverse declining Eastern Snake Plain Aquifer levels.
The agreement, reached on July 1, provides a longterm solution to a water call filed a decade ago by irrigation companies with the Surface Water Coalition against junior well irrigators with Idaho Ground Water Appropriators, Inc. The sides had been operating under terms of a methodology order requiring the Idaho Department of Water Resources director to specify a mitigation obligation for well users to meet during dry years, in which the Coalition’s senior surface users would likely be short water due to diminished spring flows into the Snake River from Blackfoot to Milner Dam, caused by well irrigation.
Well users have always avoided curtailment by providing sufficient mitigation water but entered into negotiations when it appeared they would fall short this season—prior to an extremely wet May.
Under the final terms sheet, well users will be expected to reduce their water usage by 240,000 acre feet per year, roughly equal to the average annual decline in the aquifer. According to new estimates with more precise figures, the average well user will have to curb water usage by 11 percent per year to meet the goal—slightly less than officials originally calculated.
IGWA will provide the Coalition with 50,000 acre feet in mitigation water every year, which the Coalition will use for aquifer recharge or to convert groundwater irrigation to surface water during wet years.
The agreement seeks to stabilize the aquifer within the next few years and meet its longterm goal of restoring levels to the average fill from 1991-2001 by 2026, according to sources with both IGWA and Twin Falls Canal Co. Officials say during the chosen time period, prior to a severe drought, water levels in the aquifer were about midway between the current fill and their peak in the early 1960s, when flood irrigation was common, contributing seepage to replenish groundwater, and there were fewer wells.
About 20 “sentinel” wells have been designated throughout the aquifer to monitor progress. Furthermore the state has agreed to inject an average of 250,000 acre feet of water into the aquifer annually through an expanded recharge program—involving surface water that’s intentionally allowed to seep into the aquifer through unlined canals, sink holes or special infrastructure.
The sides have until Aug. 1 to convince member districts to participate.
Source: www.capitalpress.com