The Department of Interior announced a $700 million investment in water conservation projects across the Lower Colorado River Basin that has the potential to save more than 700,000 acre-feet of water in Lake Mead. The Department of Interior announced a $700 million investment in water conservation projects across the Lower Colorado River Basin that has the potential to save more than 700,000 acre-feet of water in Lake Mead. Environment Phys.org – latest science and technology news stories