U of I expert offers water conservation tips heading into fall with drained reservoirs

By John O’Connell

University of Idaho

MOSCOW, Idaho – Absent an extremely wet winter, University of Idaho Extension educator Terrell Sorensen expects growers throughout southern and eastern Idaho will have to get creative next season to stretch meager water supplies.

Sorensen, of Power County, served as district manager of Falls Irrigation in American Falls for more than 25 years before joining UI Extension in 2015. In the late fall of each year, Sorensen authors a water outlook on behalf of the university.

Conditions are already taking shape for a challenging 2023 irrigation season. Farmers mostly drained the Eastern Snake Plain reservoir system to weather the 2022 growing season, and many canal companies have had to shut off early.

The Aberdeen-Springfield Canal Co., for example, cut off water in early September, about 40 days ahead of its usual schedule.

As of Sept. 26, the Upper Snake River reservoir system was at just 14% of its capacity, according to the U.S. Bureau of Reclamation.

Sorensen said some water-intensive crops, such as corn, are being harvested early, and the early dig sugar beets are also being harvested in areas that are going to lack irrigation water.

“We need at least 125% of the average snowpack this winter to start getting some of this storage back,” Sorensen said.

The dry season undermines efforts by the state’s groundwater irrigators to meet milestones of a major settlement agreement with surface water irrigators who have senior water rights.

A key prong of the settlement requires large-scale managed aquifer recharge – intentionally allowing surface water to seep into the aquifer through unlined canals and spill basins to replenish declining groundwater levels.

There’s been little surplus water to recharge for the past two years.

Sorensen has several tips for farmers seeking to conserve their water without sacrificing yields and profits.

First, he recommends changing cropping systems to prioritize low-water crops and short-season crops that can be harvested earlier in the year.

He finds using probes to track soil moisture can help growers avoid overwatering during the heat of summer.

Finally, he suggests that growers remove their pivot end guns, which are large sprinklers on the outer ends of pivots that spray water up to 120 feet to cover field corners.

Former UI Extension irrigation specialist Howard Neibling once estimated that farmers grow about 18% less crop on pivot corners due to uneven distribution of water by end guns.

Wind and evaporation also play a large role in the reduced efficiency of watering those areas.

Sorensen suggests that farmers who remove end guns enroll their field corners in the federal Conservation Reserve Enhancement Program, which pays farmers to stop irrigating fields throughout the duration of a 10-year contract.

There are about 12,000 acres in Idaho enrolled in CREP, which is significantly below a goal of 100,000 acres set in support of the water settlement.

Sorensen’s advice to irrigators following a dry season: “The main thing is you’ve got to be conservative on water use.

Get your leaks all stopped. Check your pivot sprinkler packages, check your nozzles, just get your system in top irrigating shape. 

“The best thing you can do is monitor your soil. You don’t want to overwater, which you tend to do when it’s hot. Switch to some different cropping systems. Maybe put fall wheat in if you can.

“Maybe look at some triticale or something for a forage crop – something that you can get off early. With alfalfa, maybe dry it up and don’t get a third crop if you’re short on water.

“You’d better look at your potatoes if you don’t have a sure water supply. The same goes with sugar beets and corn, and any intensive water crops. With corn maybe you could grow another feed that wouldn’t use as much water – maybe barley or something else that is a water-short crop.

“If you’ve got pivots, I’m big about taking the end guns off. If you put the pencil to it, with your crops out there in those corners it doesn’t pay that much to plant them and you can save a bunch of water by taking off those end guns.”

Sorensen said the reservoir storage water outlook throughout the Easter Snake River Plain doesn’t look good heading into the next water year.

“There’s going to be next to nothing left in storage,” he said.
“You look at the reservoirs now and we are really down there. American Falls is around 4% full.”