‘Watershed is saturated.’ Irrigation officials say flooding a growing concern as inflows surge.

This low crossing on Heritage Drive on the Owyhee River is blocked by high water as flows from Owyhee Dam are increased Wednesday.

NYSSA — Flows along the Owyhee River below the dam have been increased as storage of irrigation water in the Owyhee Reservoir is nearing its maximum level, and Owyhee Irrigation District officials want a controlled fill and discharge downstream.

Earlier this month, inflows into the reservoir, as measured by the U.S. Geological Survey gauge at Rome, had dropped to the point where irrigation demands were taking more water from the reservoir than was coming in. However, more recent rains have slowed those demands and increased inflows are refilling the reservoir. The body of water is projected to reach its maximum 715,000 acre feet of irrigation storage in about a week, said Jay Chamberlin, manager of the Owyhee Irrigation District during a special meeting of the Joint Board of the Owyhee Project.

As of Wednesday afternoon, flows down the Owyhee River were between 1,400 and 1,500 cubic feet per second. The joint board adopted Chamberlin’s recommendation that flows be held at 1,500 cfs, unless there is a significant increase in flows in the Owyhee River at Rome. The higher flows were expected to reach the Owyhee Junction before daylight today. Another, 1,000 cfs is being spilled through the irrigation outlet tunnel and an approximate 200 cfs will be put through the power plant at the base of the dam.

However, the flows below the dam overnight had reached more than 2,600 cfs by this morning.

The concern was about flooding fields which have been planted because channels in the river in the farmlands are choked with trees and other plant growth.

Wednesday, the flows at Rome were recorded at 3,600 cfs in the afternoon and climbing. By this morning inflows at Rome were back over 5,000 cfs.

They had been back above 3,000 cfs for more than a week because of recent rains, and heavy rains were predicted for southern Idaho from noon Wednesday through midnight, including the Owyhee Mountains, according to the National Weather Service, which had issued a flash flood warning for parts of the region.

“The watershed is saturated,” Chamberlin said during the discussion.

The joint board has scheduled meetings Thursday and Friday, depending on conditions on the Owyhee River, particularly if inflows increased.

As of early Wednesday morning, Owyhee Reservoir was 98 percent of capacity, as was Warm Spring Reservoir, which is the largest reservoir in the Malheur River Basin, according to Bureau of Reclamation Data. Beulah Reservoir was put at 99 percent and Bully Creek Reservoir is at 100 percent.


Larry Meyer is a reporter for the Argus Observer.

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