Idaho water supply outlook for 2018 looks promising

By Sean Ellis

Idaho Farm Bureau Federation

POCATELLO­ –Farmers and ranchers throughout Idaho should have an ample supply of irrigation water this year.

Last year’s phenomenal snowpack levels are still paying off as the runoff from that snowpack was enough to keep reservoirs at high levels heading into the 2018 water season.

“We are looking at an adequate water supply across the state this year,” said Ron Abramovich, a water supply specialist with the Natural Resources Conversation Service.

The abundant snowpack during the 2017 winter primed Idaho’s mountains and hydrologic system and have kept streams flowing above normal since last February, he said.

Snowpack levels in basins across the state are mostly above normal but they are well below last year’s amounts, which set records or came close in many areas.

But because of plentiful reservoir storage, even basins which received a below-average amount of snowfall this year “will still be able to have an adequate irrigation supply this year,” Abramovich said.

Streamflow forecasts range from 40 percent of average in the Owyhee basin to 120 percent in the Clearwater and Upper Snake basins, according to the NRCS’ April 1 Idaho Water Supply Outlook.

“Combining these runoff volumes with current reservoir storage, will provide adequate irrigation supplies for nearly all users (farmers, fish, power producers, river runners and more),” the report states.

In the Upper Snake River basin above Palisades Reservoir, snowpack levels were at 133 percent of average on April 24.

“We do have good snowpack, maybe even excellent snowpack,” said Lyle Swank, watermaster for Water District 1, which is supplied with water from the Upper Snake and provides irrigation water for at least 1.2 million acres of farmland in eastern and southern Idaho.

“There will be a good water supply for this upcoming water season,” he said.

There is so much water in the Upper Snake basin that water is being released from the reservoirs to prevent flooding.

In southwestern Idaho, the Payette River basin has 95 percent of normal snowpack for this time of year, said watermaster Ron Shurtleff.

“We’re looking quite well,” he said. “Our reservoirs have more water than they can hold and we’ve been making flood control releases all winter long to make space so we can capture the spring runoff.”

Pioneer Irrigation District, which gets its water from the Boise River system, gets by on natural flows in the river for as long as possible and then taps into water it has stored in reservoirs when those flows fall below a certain level.

Snowpack in the Boise River basin is only at 88 percent of normal but the amount of storage water the district has in the reservoir system will be enough to provide an adequate amount of irrigation water to PID patrons this year, said manager Mark Zirschky.

“We might not be able to rely on natural flow for as long as we normally do this year but … the amount of reservoir storage we have is looking good,” he said.  

Snowpack levels in the Owyhee River basin are at a dismal 27 percent of normal but the Owyhee Reservoir has 582,000 acre-feet of storage water, enough to guarantee irrigators their full 4-acre-foot allotment of water this year, said Owyhee Irrigation District Manager Jay Chamberlin.

The reservoir provides water to 118,000 acres of irrigated farmland in eastern Oregon and part of southwestern Idaho. Though most of those farms are in Oregon, the agricultural industry in that area is closely linked and many growers have farms in both states.

In-flows into the Owyhee Reservoir are pathetically low, Chamberlin said. While in-flows are normally about 2,600 cubic feet per second at this time of year, they are currently only at 700 cfs.

But, like other basins in the region, the reservoir entered the 2018 season with plenty of water and that will be enough to ensure Owyhee irrigators get a full supply of water this year.

 “Our only salvation this year is that we had such a good water year last year,” Chamberlin said.