Seven irrigation districts and canal companies representing the Snake River Surface Water Coalition sent a letter on April 23 to the director of the Idaho Department of Water Resources, requesting that he instruct watermasters in the Portneuf River Basin to regulate their surface water rights during the 2021 irrigation season in priority with Snake River water rights, IDWR officials said Friday.
The SWC comprises the A&B Irrigation District, Burley Irrigation District, Milner Irrigation District, North Side Canal Company and Twin Falls Canal Company. They were joined in the letter by American Fall Reservoir District No. 2 and Minidoka Irrigation District.
The SWC request for regulation is in response to a below-normal runoff forecast for the Upper Snake River. The Bureau of Reclamation/Army Corps of Engineers’ joint April forecast for the Upper Snake River predicts 80% of average runoff, or 2.6 million acre-feet. Shortages could occur to some of the SWC members on the Snake River as a result of below-normal water supplies.
The Portneuf River Basin is a tributary of the Snake River located in Southeast Idaho.
“Our clients, as well as other space holders in American Falls and upriver reservoirs may suffer reduced water supplies because of ongoing and future junior surface water diversions in (Portneuf River Basin),” wrote Travis Thompson, attorney for several members. “To that end ... the coalition requests that IDWR and the respective water districts fulfill the mandatory duties imposed by law and ensure that all senior surface water rights in Water District 01 [Snake River] are properly protected throughout the 2021 irrigation season and beyond.”
In response to the request, IDWR Director Gary Spackman said he will administer water rights in the Portneuf Basin in conjunction with the water rights in the Snake River as required by law. Idaho water rights are administered according to the Prior Appropriation Doctrine — first in time, first in right. The director, through watermasters, delivers available water to water users based on their priority dates.
When there is insufficient water to satisfy all water rights, deliveries of water to holders of water rights bearing junior priority dates are curtailed, or shut-off to ensure senior water rights receive a full supply. Many water rights authorizing diversion of water from the Portneuf River and tributaries bear priority dates that are junior to the priority dates of surface water rights on the Snake River. In the upcoming irrigation season, use of Portneuf River and tributary junior water rights may be curtailed to deliver the water to downstream senior water users on the Snake River, officials said.
Historically, the Portneuf River has been regulated separately from the Snake River. However, following the completion of the Snake River Basin Adjudication, with all water rights legally defined and decreed through the adjudication process, the department can administer both rivers in combination. Following the completion of the SRBA, and the recent SWC request for combined priority administration, 2021 will mark the first year that IDWR will combine the administration of water rights in the Portneuf Basin and the Snake River.
“For a number of years, IDWR has prepared water users in the Portneuf River Basin for regulation of Portneuf River diversions with Snake River diversions,” Spackman said. “Previously, the SWC had not requested regulation of the Portneuf River water rights. But I don’t think I have any choice now. Upon receiving the request, the law requires me to administer the water rights in priority.“Water users in the Portneuf Basin who have never been regulated before will be unpleasantly surprised by water administration in 2021,” he said. “Even so, I have a responsibility and obligation under my stewardship as IDWR director to deliver water to the holders of senior water rights on the Snake River.”
To notify Portneuf River Basin water users of the change in regulation and their possible curtailment during the upcoming irrigation season, IDWR is sending notice letters to more than 400 affected water users. If any Portneuf River junior water users are affected by the administration of water rights this year, Spackman said, there may be water available in the Water District No. 1 rental pool, or the Shoshone-Bannock Tribal rental pool. The director encourages junior water users on the Portneuf River to meet with the SWC to discuss possible mitigation for the upcoming season to allow them to divert water as they have done in past years.
While the director vowed to move forward with water administration, he said it will take time to get procedures and equipment in place.
“Instructions to Portneuf River Basin watermasters for water right administration in these smaller districts may very well result in watermaster resignations or, at minimum, resistance to regulation,” he said.