Course of the Colorado River into the Virgin River, which ran southward through what is now Overton Arm to join the Colorado River near the now-ghost town of St. Thomas, Nevada. At Hoover Dam, the Colorado turns due south through Black Canyon, a direction it will follow for the remainder of its course to the Gulf of California. It passes under the Mike O'Callaghan–Pat Tillman Memorial Bridge (Hoover Dam Bypass), the highest concrete arch bridge in the world, carrying U.S. Route 93 at a height of above the Colorado River. At the end of Black Canyon the Colorado widens into Lake Mohave, created by the
Mantasoa Dam Mantasoa Dam Mantasoa Dam is a buttress dam on the Varahina-North River, a tributary of the Ikopa River, near Mantasoa in the Analamanga Region of Madagascar. The dam was constructed by the French Business Company between 1937 and 1938. It creates Lake Mantasoa which has a surface area of . The dam itself is made of of concrete and has a reinforced buttress design. Water released from the dam supplies a regulated flow to hydroelectric power station at the Antelomita Dams downstream. A saddle dam on the north side of the Mantosoa reservoir regulates water flow into the Mandraka River