High river water continues to flow through and past Nebraska — and will for months to come.
In eastern Nebraska, the Missouri River at Omaha will be about two to three feet higher at the end of the summer and into the fall than in 2009. That will trigger a 10-day extension of the commercial navigation season for the first time since 1999.
In western Nebraska on Wednesday, the North Platte River was pouring 285 percent more water into Lake McConaughy than average. The big reservoir has been filling so quickly that officials say keeping the water level of the lake below the maximum allowed after Oct. 1 could prove difficult. That lake level limit helps avoid wind-driven wave damage to the dam.
Both the Missouri and North Platte Rivers drain huge regions of the Plains and eastern Rocky Mountains; the Missouri in Montana, the Dakotas and western Iowa, and the North Platte in Colorado, Wyoming and western Nebraska. The surging flows carried by the rivers are a combination of snow melt runoff and above-average rainfall in the upstream regions, officials said.
Runoff into the Army Corps of Engineers’ reservoirs in the upper Missouri basin was 166 percent of normal in June.
“June was the game-changer for us,’’ said Jody Farhat, chief of the corps water management office in Omaha. “We’ve accumulated a tremendous amount of water. Our current focus is to evacuate that water as quickly and as safely as downstream conditions permit.’’
The corps releases water out of its reservoir system and into the Missouri from Gavins Point Dam in northeast Nebraska. Farhat said the current level of releases at Gavins Point won’t be increased until tributaries in South Dakota and Iowa recede. Those rivers now are feeding the Missouri’s relatively high flows.
The Missouri at Omaha was about 3.4 feet lower Wednesday than its summer peak on July 1, and the Missouri will be higher than normal later this summer and fall when the corps begins flushing water out of Gavins Point. But flood flows aren’t expected to return. The river by then is expected to be two to three feet lower than its current level, Farhat said.
The plan to gradually increase releases from the dams is expected to create space in the reservoirs before the start of next year’s runoff season.
At Lake McConaughy, inflows are expected to remain well above normal for most of July, and the reservoir continues to rise, according to Cory Steinke of the Central Nebraska Public Power and Irrigation District in Holdrege, Neb.
McConaughy was 24.9 feet higher Wednesday than a year ago. It is within 19 inches of the maximum level allowed.
Keeping the reservoir below the allowed elevation will be a chore because of the combination of high releases from nearly full Wyoming reservoirs and lower than normal irrigation demand from the Platte Valley in south-central Nebraska, Steinke said.
This report contains material from The World-Herald News Service.
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