Reservoir levels start to fill as irrigation season closes

By DAVE WILKINS

Capital Press

The new water year has started off with storage levels in some Western reservoirs below their long-term averages, despite a cooler-than-normal early growing season.

Reservoir levels in Idaho, Oregon, Colorado and New Mexico were below average on Oct. 1 -- the beginning of the new water year, according to data on the National Water and Climate Center website.

Oregon reservoirs were at just 22 percent of capacity on Oct. 1, compared with a long-term average of 42 percent.

Idaho reservoirs were at 61 percent of capacity compared with an average of 67 percent.

In Washington state, reservoir storage levels were at 78 percent of capacity, slightly better than the average of 74 percent.

Reservoirs across the Northwest have begun filling again now that the irrigation season has wrapped up.

Irrigation demand was light early in the growing season because of a cool, wet, spring. But demand picked up in late summer and some irrigation districts delivered water longer than normal because many crops were behind.

"We ran a week longer than we ordinarily do," said Ted Diehl, manager of the North Side Canal Co. in south-central Idaho.

The canal company, which depends heavily on reservoir storage in the upper Snake River, shut its system down on Oct. 22.

Many farmers in Southern Idaho planted winter wheat after harvesting row crops this summer and fall, adding to irrigation demand late in the season, Diehl said.

Overall, irrigation demand ended up being about normal this year, despite the slow start, he said.

Once the spring rains passed, below-normal winter snowpack levels limited inflows to reservoirs in the upper Snake River system, said Art Hill, a hydraulic engineer with the Bureau of Reclamation in Burley, Idaho.

"After the first part of July, our inflows were really low," he said. "We were only getting about 60 to 70 percent of normal inflow."

The early growing season was marked by cool, wet weather across much of the region.

Boise area saw only three days in June with temperatures of 90 degrees or more.

and only three days in August of 100 degrees or more, according to the National Weather Service.