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Idaho water outlook looks good for irrigation season

Even the Owyhee River Basin, containing just below one-third its average snowpack, should generate adequate supply for water users, thanks to ample amounts carried over in storage in Owyhee Reservoir from past years.

By Brad Carlson

Capital Press

Published on April 13, 2018 9:55AM

Last changed on April 16, 2018 10:45AM

Irrigation water in a canal near Rupert, Idaho, in late May. Members of the Idaho Water Supply Committee say this year’s irrigation water supply should be adequate.

Carol Ryan Dumas/Capital Press File

Irrigation water in a canal near Rupert, Idaho, in late May. Members of the Idaho Water Supply Committee say this year’s irrigation water supply should be adequate.

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Idaho’s snowpack season is ending on a positive note, providing many irrigators with adequately supplied river and reservoir systems to draw from as the growing season kicks into high gear.

Most river basins are near or above their annual average for snowpack, experts said at an April 12 Idaho Water Supply Committee meeting marking the traditional end of the snow-accumulation season.

A notable exception is the Owyhee River Basin that drains a chunk of Nevada, Oregon and Idaho. But even that system — containing just below one-third its average snowpack — should generate adequate supply for water users, thanks to ample amounts carried over in storage within Owyhee Reservoir from past years.

Strong precipitation in March boosted totals as of April 1, said Troy Lindquist, a National Weather Service senior hydrologist in Boise.

“And since April 1, we’ve had several storms move through the state,” he said. “That has brought some really good precipitation, which has continued to add to our high-elevation snowpack.” In contrast, warm and dry weather at this point in the season would melt snowpack early and ultimately reduce streamflows later in the summer.

Basin snowpacks range from 31 percent of average in the Owyhee River Basin to well over 130 percent for the Clearwater Basin in north central Idaho, USDA Natural Resources Conservation Service Water Supply Specialist Ron Abramovich said. Basins are generally in good shape thanks to snowpack near or above annual averages, and good carry-over storage in reservoirs.

Water users will have adequate supply this year, Abramovich said. “We are not facing any shortages, and we are able to put an ample amount back into the aquifer,” he said.

Irrigators can expect a full season given this year’s precipitation and last year’s carry-over storage, said Brian Sauer, U.S. Bureau of Reclamation water operations manager for the Snake River Area Office in Boise.

While Owyhee Reservoir won’t fill completely because of this year’s low snowpack — it was 81 percent full on April 12 — it will have adequate irrigation supplies for this season, he said. Water users will hope for better supply conditions next year, though the large reservoir near Adrian, Ore., is designed to store about twice as much water as a single season requires.

“In general, the irrigators are looking for an adequate water-supply year to meet their needs,” said Liz Cresto, Idaho Department of Water Resources Hydrology Section supervisor and Idaho Water Supply Committee chair.

An adequate or good water year means less likelihood for conflicts among users — particularly on the Upper Snake, where above-average runoff is predicted, Cresto said. That runoff bodes well for water to be carried over to next year in reservoir storage, she said.

Reservoirs in the Boise River Basin were expected to fill to 100 percent of capacity by mid-April as the Bureau of Reclamation reduces flood-control releases.



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