SALT LAKE CITY (AP) A massive reservoir known as a boating mecca dipped below a critical threshold on Tuesday raising new concerns about a source of power that millions of people in the U.S. West rely on for electricity.

Lake Powell s fall to below 3,525 feet (1,075 meters) puts it at its lowest level since the lake filled after the federal government dammed the Colorado River at Glen Canyon more than a half century ago a record marking yet another sobering realization of the impacts of climate change and megadrought.

It comes as hotter temperatures and less precipitation leave a smaller amount flowing through the over-tapped Colorado River. Though water scarcity is hardly new in the region, hydropower concerns at Glen Canyon Dam in Arizona reflect that a future western states assumed was years away is approaching and fast.

We clearly werent sufficiently prepared for the need to move this quickly, said John Fleck, director of the University of New Mexicos Water Resources Program.

Federal officials are confident water levels will rise in the coming months once snow melts in the Rockies. But they warn that more may need to be done to ensure Glen Canyon Dam can keep producing hydropower in the years ahead.

Spring runoff will resolve the deficit in the short term, said Wayne Pullan, regional director for the U.S. Bureau of Reclamation, which manages water and power in more than a dozen states. However, our work is not done.

Though both Lake Powell and its downstream counterpart, Lake Mead , are dropping faster than expected , much of the regions focus has been on how to deal with water scarcity in Arizona, Nevada and California, not electricity supply.

For Glen Canyon Dam, the new level is 35 feet (11 meters) above whats considered minimum power pool the level at which its turbines would stop producing hydroelectric power.