Lake Mead, the Arizona-Nevada reservoir that stores water for some western U.S. states and Mexico, reached a record low on Tuesday, falling below the level that could trigger a water supply shortage.
If the U.S. Bureau of Reclamation predicts that the lake won’t rise above 1,075 ft. by January—it just hit 1,074.99—then it will announce a shortage in August, The Arizona Republic reports. Water managers are optimistic that won’t happen thanks to an unexpectedly wet spring, but the record low suggests water users are taking more from the Colorado River than it can really provide.
“This is the check-engine light,” Drew Beckwith, water-policy manager with the Western Resource Advocates, told the paper. “It really does [make critical] the fact that we have to start changing.”