The image above is a screenshot from an animation of Landsat images showing the massive growth of Las Vegas between 1984 and 2012, as well as the dramatic shrinking of Lake Mead (to the right), from which the city draws 90 percent of its water. (Click on the image to watch the animation.) To keep the water flowing, southern Nevada’s water czar has suggested that the region get federal disaster relief. (Source: Google Earth Engine) The U.S. Bureau of Reclamation made an historic announcement today: It is cutting its water releases from Lake Powell to their lowest levels since the giant reservoir on the Colorado River began to fill in the 1960s. Thanks to increasing demand for Colorado River water, and decreasing supply resulting from profound drought, Lake Powell has dropped to less than half full. To help slow the decline, the Bureau of Reclamation will reduce the amount of water Lake Powell releases downstream toward Lake Mead in 2014 by almost 1 million acre-feet. (An acre-foot is roughly the amount of water a U.S. household uses in a year.) But that means Lake Mead, the other giant hydrological savings bank on the river — and the supplier of 90 percent of the water used by Las Vegas — could be headed for even more serious trouble in coming years. That prospect has prompted the water czar for southern Nevada to float the idea of asking for federal disaster assistance to cope with dwindling water supplies. Quoted in the Las Vegas Review-Journal, Pat Mulroy, head of the Southern Nevada Water Authority, compared the drought and its effects to Hurricane Sandy, which inundated large parts of the Northeast in fall of 2012: