The West has been suffering from a severe drought since 2013 and, in some cases, much longer than that. Conditions are particularly acute in California, where close to 60% of the state is experiencing "exceptional" drought after three years of below average rainfall. This is the worst category according to the U.S. Drought Monitor.

According to a new study published in the journal Science, the regional drought has cost the West about 240 gigatons of surface to near-surface water, or about 63 trillion gallons of water. This is equivalent to covering the entire western U.S. with a four-inch layer of water, the study found.

The study, which used GPS data, found that in response to the lack of surface water, land masses across the West have been rising, especially in California's Sierra Nevada Mountain range. In other words, the drought is actually moving mountains.

On August 26, Trinity Lake, which can hold 2.4 million acre-feet of water, had just 29% of capacity, and the Shasta reservoir on the Sacramento River had 30% of its capacity, according to the California Department of Water Resources. The Oroville reservoir, which can hold 3.5 million acre-feet of water, was at just 31% of capacity.

Lake Mead, which is North America's largest manmade reservoir, dropped below 1,082 feet above sea level in July, setting a record for the lowest it's been since the Hoover Dam was built in the 1930s. The reservoir, which helps supply water to Las Vegas, has been depleted by a drought that has lasted for more than a decade in the Southwest. Climate change is expected to continue to push that region into a hotter and drier era.

These before and after images show the startling decline in California's lakes and reservoirs during the intense drought.

In this before-and-after composite image, (Left) full water levels are visible in the Bidwell Marina at Lake Oroville on on July 20, 2011 in Oroville, California. (Photo by Paul Hames/California Department of Water Resources via Getty Images). (Right) Low water levels are visible in the Bidwell Marina at Lake Oroville on August 19, 2014. (Photo by Justin Sullivan/Getty Images)



In this before-and-after composite image, full water levels are visible behind the Folsom Dam at Folsom Lake on July 20, 2011 in El Folsom, California. (Photo by Paul Hames/California Department of Water Resources via Getty Images). Low water levels are visible behind the Folsom Dam at Folsom Lake on August 19, 2014. (Photo by Justin Sullivan/Getty Images)"

In this before-and-after composite image, the Green Bridge passes over full water levels at a section of Lake Oroville near the Bidwell Marina on July 20, 2011 in Oroville, California. (Photo by Paul Hames/California Department of Water Resources via Getty Images). The same location seen on August 19, 2014. (Justin Sullivan/Getty Images)"

In this before-and-after composite image, (Left) boats are moored at the Lake Mead Marina on July 25, 2007 in the Lake Mead National Recreation Area, Nevada. (Photo by Ethan Miller/Getty Images). (Right) A pair of rest rooms on pontoon floats rest on dirt in Boulder Harbor where the Lake Mead Marina was once located on July 17, 2014. (Photo by Ethan Miller/Getty Images)"