South-central Idaho water outlook improves

February storms added much-needed precipitation to basins in southern Idaho, bringing many closer to normal and improving the outlook for irrigation supplies.
Carol Ryan Dumas

Capital Press

Published on February 25, 2014 12:30PM

The water picture for much of Idaho was depressing a month ago, experts say, but February storms have improved the outlook.

“We’re doing better, a lot better,” Ron Abramovich, water supply specialist with Idaho Natural Resources Conservation Service, told farmers and ranchers at a water efficiency and drought workshop in Shoshone, Idaho, on Monday.

Precipitation is in a yo-yo pattern. January was dry, then storms opened up. The Pacific Northwest and California are in a wet pattern, even seven days out, he said.

It won’t do much to get California back on track, but it is helping Idaho, he said. California remains locked in a drought.

September Precipitation was 200 to 300 percent of normal in Idaho. But October through December was dry and the state lost all of that September soil moisture, he said.

The dry spell continued in January, with NRCS reporting some of the smallest snowpacks on record in southern Idaho, even with near normal snowpack in the Clearwater and Upper Snake Basins.

February storms through Feb. 19, however, brought southern Idaho snowpacks to 100 to 200 percent of normal monthly precipitation, bringing snowpacks closer to normal, with 10 days left in the month, he said.

The Feb. 25 snow water equivalent measures show The Big Wood Basin is at 85 percent of normal, up from 55 percent on Jan. 30. The Little Wood is at 66 percent, up from 53 percent on Jan. 30. And the Upper Snake Basin, which supplies irrigation water to southern Idaho, is at 135 percent of normal, up from 100 percent on Jan. 30.

Things have definitely picked up and look much better than a month ago, NRCS hydrologist Karl Wetlaufer said on Tuesday.

The Boise and Big Wood basins are now looking reasonable compared with what NRCS thought a month and a half ago, he said.

Precipitation in the first few weeks of February was more than the average for the entire month across Idaho but particularly in southern Idaho where precipitation was really needed, he said.

As of last week, precipitation has slowed down for some basins in southern Idaho, he added.

The Big Wood snowpack is still below normal, but there’s a chance of it getting to normal if wet weather continues for another month and a half, Abramovich said.

The snowpack would need 171 percent of normal precipitation for the next month to reach its normal April 1 peak. There’s probably less than a 50 percent chance of that, and it gets slimmer with each day of sunny weather, he said.

The Little Wood snowpack is still well below normal and would need 200 percent of normal precipitation for the next month to reach a near-normal peak by April 1, he said.

The Big Lost jumped up quite a bit but is still very low compared to median, he said.

Adequate water supplies for surface irrigation in south-central Idaho could be a challenge. With reservoir levels as of Feb. 14, runoff into reservoirs will need to be 85 percent of normal in the Big Wood Basin, 45 percent of normal in the Little Wood and 99 percent of normal in the Big Lost. Some shortages are likely in all three basins, he said.


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