Plunging water levels in Lake Mead and Lake Powell could negatively affect millions of people. The former at one point this year dropped to less than 150 feet from "dead pool" status – when the volume falls to a level so low that water cannot flow downstream from the dam. Andrea Gerlak, professor of geography, development and environment at the University of Arizona, said Lake Mead is "dangerously close" to hitting a low enough elevation for it to stop turning the turbines, and producing electricity. "But, more importantly – if and when Hoover Dam stops producing electricity – it will call into question our very assumptions for how we manage water and energy in the southwestern U.S."