Reservoir levels low

East Idaho reservoir levels are the lowest they’ve been since 2007. American Falls Reservoir has been drawn down to 11 percent.


While East Idaho reservoir levels are the lowest they’ve been since 2007, other state efforts to recharge the East Snake Aquifer are on track with a five-year plan.

Mathew Weaver, a senior water engineer with the Idaho Department of Water Resources, recently gave the Idaho Water Resource Board an update on recharge efforts for the Snake River region in Lewiston.

“Good news, natural flows were up this year,” Weaver said about late season samples from various waterways to the board.

Weaver said later in a phone interview, the state’s recharge efforts for the East Snake Aquifer may play a small part in the higher reach gain levels being seen.

There are places along the Snake River where river water meets injection sites into the aquifer and other places where the aquifer meets the river.

“Return flows in the Snake River between Idaho Falls to Milner (Dam), reach gains are up this years,” Weaver said. “(We) had seen steady decline so this was the first year we’ve seen some nice return flows late in the seasons. … It’s hard to imagine recharge efforts in the past few years aren’t contributing.”

Water storage along the Upper Snake River is down this season compared to last year’s abundance from a strong snowpack in winter 2010-2011, according to water master for District No. 1 Lyle Swank.

Swank said this time last year, the American Falls Reservoir was about 60 percent filled and Palisades was about 95 percent full. The system of about nine reservoirs was about 78 percent filled in 2011.

“Today, (the) total reservoir system is 32.8 percent full for the Upper Snake River,” Swank said. “American Falls is our biggest (it’s) only 11 percent full, Palisades which is 19 percent full is second biggest. Trying to keep the reservoirs filled is hard if you don’t get a good snow pack.”

Swank said the current reservoir storage is typical of a second year drought season.

“It’s quite a bit different than it was a year ago,” Swank said. “We had a big snow pack and it came off late. … We didn’t have a real good snow pack this year and not much in the valley, so we had a startup in demand and had a long, hot, dry season.

“We got through 2012 pretty good. Our reservoir storage is good right now. We really do need a good snowpack up in the mountains this year.”

The hope of a solid snowpack this winter is still unknown, but early indications point to El Niño type weather from the National Weather Service’s website, which for East Idaho, has typically meant mild weather, Swank said.

The National Weather Service’s Climate Prediction Center predicted somewhat higher than normal temperatures for East Idaho going into winter.

“Climate markers are looking a little bit bleak. We’re entering into an El Niño type model (indicating) higher temperatures,” Weaver said to the Idaho Water Resource Board.

Mike Beus, the Bureau of Reclamation operations manager for the Upper Snake Field Office, said the bureau had similar numbers for water storage, adding that some storage could still drop one or two percent before the flows stop.

“The only concern about being as low as we are right now is we got here from a very good carry over and snowpack in just one year, if this were a second year drought we’d say this is a pretty good situation,” Beus said.

Swank said in 2012 the reservoirs showed their value by retaining water from 2011 and supplementing the precipitation.

“It’s really valuable for the people who depend on it for crops or agricultural processing industries, too,” he said.

Swank said using the “big water” in 2011 to not only fill reservoirs, but to help recharge the aquifer, no doubt had a good effect on this year’s drought conditions.

“Anything that was recharged this last year produced a positive benefit for 2012,” he said.

Weaver said since the 1990s there has been an effort to recharge, or put water back into the East Snake Plain Aquifer, but efforts have been somewhat sporadic.

“The Eastern Snake Plain Aquifer, since the late 1950s, has been in slow decline,” Weaver said.

Increased use and demands on the aquifer have been diminishing its supply. In January, the Idaho Water Resource Board adopted a five-year plan to recharge the East Snake Plain Aquifer by 600,000 acre feet of water.

Weaver said before irrigation season began, 107,000 acre-feet of water had been routed to charge the aquifer. Weave anticipated another 20,000 acre-feet would be used in the effort by the end of the season.

He said a number of canal companies have helped in the effort by letting the recharge water soak into the ground through canals, in addition to wells and springs.

Weaver said beginning in 2019, phase two of the recharge effort will increase to 250,000 acre-feet for the next 10 years.

For more information on available water data, visit http://www.idwr. and click on the water data link.