Lake Powell on the border of Utah and Arizona supplies water to millions across the southwestern United States. Long-term dry conditions put the reservoir at a historic low in 2021. Landsat 8 imagery from 2017 shows the water's elevation at 3,628 feet. The reservoir on that day was at 60.3% of full capacity. 4 years later the level is 84 feet lower, with capacity down to 29.5%. Landsat will continue to monitor the reservoir from above.