As summer winds down, concern rising over ‘multiyear drought,’ Idaho water managers say

Idaho water managers are warning of the possibility of a lasting drought following the second-driest March-to-July period in the state’s recorded history.

According to an Aug. 6 drought condition update from the Idaho Department of Water Resources, officials are more worried than ever that the state’s drought won’t resolve quickly.

“With storage being rapidly depleted across the state, concern is rising that we may be entering into a multiyear drought,” wrote hydrologist David Hoekema in the report.

Hoekema said many reservoirs have been depleted this year, which means the state’s water supply will start off the next water year — which begins in October — already at a deficit. He mentioned that the Mountain Home Irrigation District and Big Wood Canal Company shut down water deliveries from storage in June, and said the Little Wood River Reservoir in Blaine County, the most drought-stricken part of the state, was at 2% storage capacity on Aug. 6.

Water resource managers in the Treasure Valley have also warned that they’ll likely have to cut the irrigation season short by a month or so. They’ve urged people to water lawns less often and find other means of conserving the dwindling water supply.

Hoekema said that when the irrigation season ends, officials can analyze what kind of snowpack Idaho will need this year to bounce back from the drought.

“On a positive note, the tropical Pacific is lining up for another La Niña this winter,” the hydrologist wrote in his report. “A La Niña typically brings higher than normal precipitation to northern Idaho, but could result in deepening drought across the southwestern United States and up into the Bear River basin.”

According to Hoekema, another La Niña system last winter provided “a near average” snowpack for Idaho by March 1. It was the scarce precipitation since then — which set record lows at snow telemetry measurement sites across Idaho and the Northwest — that created a rapidly accelerating drought that took water managers by surprise.

The report said the heart of Idaho’s drought is in the state’s central mountains, which also saw drought in 2020.

“Runoff records indicate that the Big Wood, Big Lost, and Little Lost basins may set record lows this year,” Hoekema wrote. “In other words, 2021 is likely to be considered the drought of record in those basins.”