How bad is the drought in the western United States? A breathtaking representation of the record dry spell is in images of Lake Mead, the reservoir formed by the Hoover Dam on the Colorado River. NASA satellite images (below) from Landsat 7 and Landsat 8 show the difference in lake levels between August 2000 and August 2021.
Comparative Landsat satellite imagery of Lake Mead August 7, 2000 (left) and August 9, 2021 (right). Photo credit: NASA
According to the US Bureau of Reclamation, the water level in the reservoir, which supplies drinking water to millions of people in California, Arizona, Nevada, and part of northern Mexico, was at its lowest level since the lake was created by the Colorado River dam in 1935 .
Data shows that Lake Mead was only 35 percent full on August 22, 2021. The low water level comes at a time when 95 percent of the land in nine western states has experienced some drought (64 percent are extreme or worse). It continues a 22-year mega-drought in what is possibly the region’s worst drought in twelve centuries.
The image from 2021 shows brown “seams” along the coastline in 2021, which are areas of the lake floor that would be under water when the reservoir is filled closer to its capacity limit. This phenomenon is often referred to as the “bathtub ring”.
The sea level data shown below indicates that the water level at Hoover Dam was 1,067.65 feet (325 meters) above sea level in late July 2021, the lowest since April 1937, when the lake was still being filled. The elevation in late July 2000 – around the time of the Landsat 7 images – was 1,199.97 feet (341 meters).
Data from the US Bureau of Reclamation and NASA.
At maximum capacity, Lake Mead will reach a height of 1,220 feet (372 meters) near the dam and would hold 9.3 trillion gallons (36 trillion liters) of water. The lake last reached full capacity in the summers of 1983 and 1999. Since then it has been in decline.
Lake Mead is the largest reservoir in the United States and part of a system that supplies at least 40 million people with water. The record low in the reservoir means less water will be distributed to some states in the 2022 water year, and the US Bureau of Reclamation said “the reductions are the first” scarcity “statement – evidence of the severity of the drought and low water levels Conditions of the reservoir. “
Sources and further reading: NASA Earth Observatory, US Bureau of Reclamation
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