April rain turned the Foothills green — but did little to help farmers, fire watchers

April showers filled May reservoirs, but not enough to salvage a dreadful water year for farmers across southern Idaho — or to offset mounting fears of the wildfire season ahead.

While parts of the Treasure Valley saw twice the normal precipitation last month, drought still deepened across much of the state, according to Idaho Department of Water Resources hydrologist Hannah Adams.

“There isn’t a place in Idaho that isn’t in some form of drought,” Adams said during a monthly interagency meeting on water supply Wednesday in downtown Boise. That includes a growing swath in “extreme drought” from the state’s southern border into the eastern Snake River Plain and a band of “exceptional drought” — the driest distinction in the U.S. monitoring system — across parts of Owyhee, Elmore and Twin Falls counties.

Those areas encompass some of Idaho’s most productive agricultural land, and farmers are already making difficult decisions, Erin Whorton, a water supply specialist with the federal Natural Resource Conservation Service working in Idaho, told the Statesman in an interview.

Farmers in the Salmon Falls tract, which runs from the Nevada border to the Snake River west of Twin Falls, are fallowing fields, she said, leaving them empty rather than risking plants dying without irrigation.

“There’s not enough water to even get a crop,” she said. Whorton recently met with water managers in the area. “This is the most stressed they’ve ever seen water users,” she said.

“These are the folks that saw the impacts earliest, and are facing it most severely,” she said — though other areas aren’t far behind.

The Big Wood River Subbasin, which covers 1,500 square miles in the mountains of Blaine, Lincoln, Camas and Gooding counties, has enough water for about 40-45 days of irrigation, according to Whorton. That’s not enough to grow the region’s chief crop, corn, she said. A manager for the Big Wood Canal Company did not immediately respond to a request for comment.

Magic Reservoir, which in years past has buttressed water deliveries into September, was only 37% full on Wednesday, according to the company.

What’s it mean for Boise?

The Treasure Valley’s reservoir system is in better shape than most.

Anderson, Arrowrock, Lucky Peak and Lake Lowell reservoirs, which as a group hold some 325 billion gallons of water, were collectively 97% full on Thursday, according to data from the federal Bureau of Reclamation.

Experts, though, see little reinforcement on the way.

Rivers are running low for this time of year, including the Boise. Natural flow at Lucky Peak on Wednesday ran 57% of normal on Wednesday, according to the U.S. Geological Survey. Combined with what’s in reservoirs, that should be fine to get irrigators through this summer, but set up a high-stakes winter in 2026-27.

In a typical year, the alpine snowpack serves as a “huge extra reservoir,” Whorton said, sending water downhill on what amounts to a time release. Normally, the mountains hold more water than any reservoir system can hope to capture. The Boise Basin’s snowpack has been measured to be 30% larger than its reservoir capacity, according to the Treasure Valley Water Atlas from the University of Idaho and Boise State. In other basins, like the Upper Snake, it’s often three times larger, Whorton said.

That runoff fills reservoirs even as they release water to irrigators downstream. This year, with snowpack at or close to historic lows, most parts of Idaho don’t have that backup.

“Having snow melt off earlier, and taper off sooner, means water is just not available,” Whorton said. Spring rain, “while generally helpful,” can’t compensate.

“It’s great to see how green the Foothills are, but it wasn’t anything that can make up for our snowpack,” she said.

In April, Idaho Department of Water Resources hydrologist David Hoekema expected the Treasure Valley to get through the season by drawing its reservoir system close to zero. Little presented this week seemed to change that projection.

“There’s some snow left to feed the rivers, longtime Idaho water supply expert Ron Abramovich said Wednesday, “but not a whole lot.”

Signs point to warm, dry summer

Longer term, forecasts point to El Niño developing through the summer and into next winter, said Troy Lindquist, a hydrologist with the National Weather Service. Pacific warming that drives the designation tends to favor warmer, dryer conditions in Idaho, he said.

“Based on the model, I wouldn’t bank on above normal or even normal precip,” in the months ahead, he said. “I would love to see us above normal, or even normal — but I wouldn’t bank on it.”

That’s a grim combination to fire watchers, including Christina Lazar from the Idaho Office of Emergency Management.

While the Treasure Valley’s wet spring helped fill reservoirs, it also supercharged vegetation. Gauges at the Boise Airport on Wednesday had received about a year’s worth of water already, and it’s painted in green on the hills, Abramovich said, “a new crop of cheatgrass for fire season.”

Lazar is planning on wildfires to spark earlier than usual in eastern Washington and Oregon, and is monitoring drought conditions across southern Idaho.

“My mind is going a mile a minute,” she said.