The floor rumbled under Mark Cook. His legs vibrated as he stood in a tunnel tucked into the thick base of Hoover Dam, 430 feet below the tourists looking out over Lake Mead. Beneath him, water roared through steel pipes 13 feet tall. Nearby, heavy turbines hummed with mechanical intensity. “We’re moving some good water today,” Cook, the dam manager, said proudly. Moving water means making electricity. But the drought is making that harder to do. The lack of water has put a serious crimp in the hydroelectric line at Hoover Dam and other power plants across the West, limiting an inexpensive and pollution-free energy source that once was considered endless. Power capacity at Hoover Dam, on the Arizona-Nevada border, has dropped nearly 25 percent since 2000. In California, home to 287 hydroelectric plants and where almost half the state today is classified as being in […]