Declining flows in the Colorado River

The amount of water in the Colorado River has declined over the last century. The U.S. Bureau of Reclamation estimates the natural flow of the river, which is the amount of water that would flow past Lees Ferry in a given water year if there were no upstream diversions. The water year begins on Oct. 1 -- when snow begins to accumulate -- and ends Sept. 30, when it has all melted.

Colorado River flow at Lees Ferry, Ariz.
Millions of acre-feet