LEAD: The Colorado River's Lake Powell reservoir remains well below full capacity after a winter of generally below normal snowfall in the Rocky Mountains.
1. In 1999, water levels in Lake Powell were relatively high, and the water was a clear, dark blue.
2. But images taken by USGS-NASA Landsat satellites over the last 17 years shows the reservoir levels falling, rising and falling as of result of spring snow melt in the headwaters of the Colorado Rockies.
3. Lake Powell water levels in mid-June 2015 are about 80 feet lower than the peak level of 1999.
TAG: The Colorado River Basin provides water to roughly 40 million people in 7 states and Mexico.