The National Weather Service said the river dropped more than a foot at Brownville to 42.97 feet Friday afternoon after the breach Thursday evening upstream in northwest Missouri. Before the breach, the river had been 44.8 feet deep at Brownville.
The river would have to rise to 46.5 feet before it reaches Cooper, which is owned by the Nebraska Public Power District, but the plant would be shut down as a precaution if the river reached 45.5 feet.
NPPD spokesman Mark Becker said the plant continues to operate at full capacity.
The weather service predicted that the river at Brownville will rise over the weekend back to a similar level to earlier this week. The Army Corps of Engineers predicts it will rise another 3 to 5 inches on top of that by early next week.
The corps has been releasing water from dams upstream where heavy spring rain and snow melt have bloated the waterway, causing a rapid rise in the river elsewhere. Releases at Gavins Point Dam in South Dakota hit 160,000 cubic feet of water per second on Thursday, and the corps planned to continue releasing water at that rate until at least August.
The river is expected to remain 5 to 7.5 feet above flood stage in Nebraska and Iowa throughout the summer, and water levels could swell more than 10 feet above flood stage at places in Missouri.
Experts with the National Weather Service and the corps have said that levee breaches will provide only temporary decreases in water levels because there is still so much water flowing downstream. Once the water flowing through a failed levee spreads out, the pressure will build up and the river will rise again.
NPPD officials have been monitoring river levels closely during the flooding, and they have already brought in more than 5,000 tons of sand to build barricades protecting the Cooper plant and its access roads. Some internal doorways have also been barricaded with flood gates to protect equipment.
Last Sunday, Cooper nuclear plant sent a low-level alert to the Nuclear Regulatory Commission, called a "notification of unusual event," because of the rising river, so regulators are also watching the situation closely.
Nebraska's other nuclear power plant, Fort Calhoun, issued a similar notice on June 6. That power plant, about 20 miles north of Omaha, remains shut down because of concerns about the water level there.
The river at Blair, near Fort Calhoun, was 32.5-feet-deep Friday morning, which is 6 feet above flood stage, causing moderate flooding of low-lying areas. The Omaha Public Power District, which owns Fort Calhoun, said a series of protective barriers have stopped the advance of floodwaters and protected the nuclear plant.
Nuclear Regulatory Commission officials say both NPPD and OPPD have taken appropriate measures to protect their nuclear power plants.
The commission said Friday that Chairman Gregory Jaczko will visit Cooper on Sunday and tour Fort Calhoun on Monday to check out the measures they've taken to battle flooding along the Missouri River. He also will take a helicopter tour of flooding on the river on Monday.
NOAA Advanced Hydrologic Prediction Service
