Lake Mead shrank to a historic low Tuesday night, igniting concerns of a possible water supply shortage.

Water levels dropped to , the Arizona Republic reported, the lowest it’s been since 1937.

Over the course of its history, Lake Mead has been over-appropriated, causing a the current drought affecting the West has only made worse, according to the Las Vegas Review-Journal.

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The lake, which runs along the border between Arizona and Nevada, is a primary water source for several Western states. The aforementioned math problem is such that the , says the National Park Service, supplying millions in the region.

Yet despite low water levels, the Southern Nevada Water Authority is slated to complete a third water intake or this summer, which will keep water flowing to communities regardless of falling levels.

Lake Mead is fed by the Colorado River, and this historic low reveals the river is facing the same issue: it is providing more water than it is receiving from natural resources, including runoff and precipitation.

“This is the check-engine light,” Drew Beckwith, water policy manager with Western Resource Advocates, told the Arizona Republic. ”It really does make critical the fact that we have to start changing.”

MORE ON WEATHER.COM: Lake Mead Drought

Lake Mead in Historic Drought

A buoy warning 'no boats' stands on dirt at the abandoned Echo Bay Marina on July 13 in the Lake Mead National Recreation Area, Nevada. The marina closed last year after no businesses wanted to operate it, in part due to falling water levels according to the National Park Service. (Photo by Ethan Miller/Getty Images)