A wet May across most of Idaho contributed to a good water year and plentiful water supplies this growing season.
Above-normal precipitation was observed across the southern half of the state in May, especially south of the Snake River Basin, according to the latest water supply outlook by Idaho National Resources Conservation Service.
There are more than adequate water supplies in the southern half of the state, where most of the state’s agriculture occurs, Danny Tappa, NRCS hydrologist, told Capital Press.
Water-year totals are above normal for all basins south of the Clearwater Basin. Reservoirs are full and there’s melting snow, he said.
“It’s a good-looking water picture for this growing season,” he said.
Several remote SNOTEL stations set records in May for total monthly precipitation, mostly from the Owyhee Basin to the Oakley Reservoir and Raft River, he said.
“That’s particularly impressive since the first half of the month was record dry for all of the state,” he said.
It’s all positive for agriculture, he said.
The only clouds in the picture are for the far northern part of the panhandle, where the story is “kind of a building drought,” which is abnormal as that area usually has the wettest weather, he said.
“It’s been an extended run of dry, dry conditions in the far northern panhandle,” he said.
That area largely missed out on May precipitation, continuing a dry trend for much of the last 12 months, he said.
As a result, the U.S. Drought Monitor has moved the region’s status into moderate drought.
The seasonal mountain snowpack peak this year exceeded normal across most of the state — except for the Clearwater Basin and the Panhandle. Widespread snowmelt began in April and continued through May. In some instances, a loss of more than 30 inches of snow water content was observed in May.
Significant snow remains in the higher elevations, above 7,000 feet, from the Salmon River Basin south and into western Wyoming and the Snake River headwaters.
Reservoirs are at or near capacity, and some flood-control releases are still underway, he said.
As of June 9, the Upper Snake River system was at 93% of capacity. The Boise River system was at 97%, and the Payette River system was at 96%, according to the Bureau of Reclamation.
Most systems are at or near capacity. Any further slowdown in snowmelt and additional precipitation would extend the spring runoff season and result in greater carryover, he said.
That would provide a decent start on next year’s water supply, which is great news, he said.