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
Welbedacht Dam dam wall. For various reasons, however, constructing a smaller scheme on the Caledon River was implemented before completion of the Vanderkloof Dam. The Welbedacht Dam on the Caledon River was constructed as the main storage element of the CMRGWS and water is abstracted from this dam for transfer to Bloemfontein and various smaller users along the way. The Welbedacht Dam is a concrete barrage-type dam on the Caledon River, which was designed and constructed by the Department of Water Affairs. The dam has a catchment area of some 15 245 km² with a natural mean annual runoff (MAR) around 1210