An important Colorado River reservoir has fallen below a level that federal water managers were trying to maintain for hydropower generation. 

Lake Powell on the Arizona Utah border fell below 3,525 feet this week. That marks the lowest level since the U.S. government first built Glen Canyon Dam 60 years ago. 

Federal officials are confident that spring runoff will make up for the shortage. But it raises concerns not just about a water shortage in the West but electricity shortfalls as well.

Millions of people in seven states rely on power generated at Glen Canyon Dam.