DENVER (AP) – An interim report on a study of potential imbalances in Colorado River water supply and demand predicts challenges from climate change.

The U.S. Bureau of Reclamation and agencies in the seven states in the river basin plan to release a final report next year. But an interim report released Monday says that under one scenario, droughts lasting at least five years are projected 40 percent of the time over the next 50 years, which could reduce streamflows.

The interim report documents progress on the study through Jan. 31. It doesn’t mention this year’s deep mountain snowpack in parts of the West.

More than 30 million people in Arizona, California, Nevada, Colorado, New Mexico, Utah and Wyoming depend on water supplied by the Colorado River and its tributaries.

(Copyright 2011 by The Associated Press.  All Rights Reserved.)