… Between its high Rockies headwaters and its Sonoran Desert delta, 1 to 2 million acre-feet of water evaporates each year in the Colorado River Basin. That’s a big gulp in a watershed where seven thirsty U.S. states and northern Mexico skirmish for their share of an overallocated, shrinking water supply. And the evaporation will only increase as the Southwest grows hotter and drier. To cut their losses, a growing number of Western water managers want to install solar-paneled canopies over canals and even flotillas of solar panels on reservoirs to turn the sun’s rays into electricity before they hit the water.