this spring, heavy rains and high snowpack levels in Montana, northern Wyoming, and the western Dakotas have filled reservoirs to capacity, and unprecedented releases from the dams are now reaching Omaha and other cities in the Missouri River valley. Floodgates that haven't been opened in 50 years are spilling 150,000 cubic feet per second -- enough water to fill more than a hundred Olympic-size swimming pools in one minute. And Fort Calhoun isn't the only power plant affected by flooding on the Missouri: The much larger Cooper Nuclear Station in Brownville, Nebraska, sits below the Missouri's confluence with the Platte River -- which is also flooding. Workers at Cooper have constructed barriers and stockpiled fuel for the plant's three diesel generators while, like their colleagues at Fort Calhoun, they wait for the inevitable.