You can't empty Lake Mead, so its current 29% of capacity is...

You can't empty Lake Mead, so its current 29% of capacity is irrelevant. If it continues to drop from 1,040 feet above sea level to 895 feet, there won't be enough to run the turbines at Hoover Dam and much of Nevada, Arizona and California will be without power. But that doesn't really matter, because no one can use Colorado River water for new mining anyway. It has to come from groundwater, which is being depleted rapidly. Unfortunately, groundwater use in Mohave County is largely unregulated. BLM might take it into consideration if a mining application were submitted, but they don't have a history of considering such long-term consequences.