How bad is the drought in the western United States? A stunning depiction of the record dry spell comes 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.
According to the U.S. 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 measured at its lowest level since the lake was created with the damming of the Colorado River in 1935.
Data shows that as of August 22, 2021, Lake Mead was filled to just 35 percent of its capacity. The low water level comes at a time when 95 percent of the land in nine Western states is affected by some level of drought (64 percent is extreme or worse). It continues a 22-year megadrought that may be the region’s worst dry spell in twelve centuries.
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The image from 2021 shows tan “fringes” along the shoreline in 2021, which are areas of the lakebed that would be underwater when the reservoir is filled closer to capacity. This phenomenon is often referred to as a “bathtub ring.”
The lake elevation data, shown below, says that at the end of July 2021, the water elevation at the Hoover Dam was 1067.65 feet (325 meters) above sea level, the lowest since April 1937, when the lake was still being filled. The elevation at the end of July 2000—around the time of the Landsat 7 images – was as 1,199.97 feet (341 meters).
At maximum capacity, Lake Mead reaches an elevation 1,220 feet (372 meters) near the dam and would hold 9.3 trillion gallons (36 trillion liters) of water. The lake last approached full capacity in the summers of 1983 and 1999. It has been dropping ever since.
Lake Mead is the largest reservoir in the United States and part of a system that supplies water to at least 40 million people. The record low levels in the reservoir means less water will be portioned out to some states in the 2022 water year, and the U.S. Bureau of Reclamation said that “the reductions represent the first “shortage” declaration—demonstrating the severity of the drought and low reservoir conditions.”
Sources and further reading: NASA Earth Observatory, U.S. Bureau of Reclamation