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Lower Missouri River flows high, Lake Sakakawea release reduced

Too much water downstream

The amount of water being released through Garrison Dam was reduced from 20,000 cubic feet per second to 15,000 cfs Tuesday. The reason for the cut was to reduce the amount of water flowing to points downstream on the Missouri River where heavy rainfall threatens to swell reservoirs.

According to the U.S. Army Corps of Engineers, rainfall over much of central North Dakota, South Dakota and Nebraska has run from 200-600% more than normal during the past week. The result is that increased runoff pouring into Lake Oahe, Big Bend, Fort Randall and Gavins Point impoundments has led to a need to push more water through the system to alleviate potential flooding.

“We need to ensure we have space available to manager additional runoff,” said John Remus, chief of the Missouri River Basin Water Management Division at Omaha, Nebraska.

Reservoirs on the Missouri River, upstream to downstream, are Fort Peck, Lake Sakakawea, Lake Oahe, Big Bend, Fort Randall and Gavins Point which is located near Yankton, S.D. Gavins Point releases were increased from 60,000 cfs to 65,000 cfs Tuesday and were scheduled to be increased to 70,000 cfs today. The increased releases are expected to slow rising water levels at impoundments downstream from North Dakota.

The cutback in the release rate from Garrison Dam will likely have minimal effect on Lake Sakakawea, at least in the short term. Lake Sakakawea was forecast to end May at a level of 1,847.2 feet and was at 1,847.19 Tuesday. The reservoir’s three-week outlook, updated last Friday, calls for an end of month reading of 1,847.5. However, expectations are that projection will be surpassed slightly in the next few days and be reflected in an expected revised forecast to be issued by the Corps.

At this time there is ample storage available in Lake Sakakawea, which remains below its exclusive Flood Control Zone of 1,850 to 1,854 feet.

“Right now we have the storage capacity,” said Todd Lindquist, Garrison Dam project manager, USACE.

Lake Oahe has entered its exclusive Flood Control Zone. The level of that reservoir Tuesday was 1,618 feet. Spillway level for Lake Oahe is 1,620 feet. Fort Peck, located above Lake Sakakawea, stood below its exclusive Flood Control Zone at 2,243.11 feet Tuesday. Spillway level at Fort Peck is 2,250 feet.

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