When high temperatures dried out much of the country last summer, barges were restricted to floating at a depth of nine feet instead of 12 feet. Recent snows have pushed water levels up enough to allow barges to run at 12 feet of depth again.

McCulloch is afraid this might not hold, when the summer heat returns.

Water where it's not needed

As the current storm reaches the Atlantic coast, dumping snow on the nation's capital, the white precipitation should become slushier and deliver more moisture per foot of snow, according to CNN's Weather Center.

The District of Columbia and Baltimore are bracing for potentially significant accumulations, according to the National Weather Service. Snow plows have been readied.

Airlines have canceled flights to and from Washington's Dulles airport ahead of the storm's arrival: United 650, U.S. Airways 350, American 20.

But by the time the storm gets there, it could turn to rain.

The Northeast doesn't need it. It is already plenty moist, Drought Monitor said.

In the parched Plains states, snow hasn't helped enough.

They could use that rain.