For eons a great river carved its way through the wilderness, a murky ribbon of churning, silt-laden water. Then came man with his gigantic dams and azure, sprawling lakes. Water, desert, dams, and mountains--astonishing contrasts in an immense land where nature, in the final analysis, is still in control. Lake Mead National Recreation Area, located in southern Nevada and northern Arizona, was established in 1964. It includes Lake Mead (Hoover Dam) and Lake Mohave (Davis Dam).