Parker Dam is a concrete arch-gravity dam that crosses the Colorado River downstream of Hoover Dam. Built between 1934 and 1938 by the Bureau of Reclamation, it is high, of which are below the riverbed (the deep excavation was necessary in order to reach the bedrock on which the foundation of the dam was built), making it the deepest dam in the world. The portion of the dam above the foundation stands tall, making it the only dam in the world that stands more underground than above ground. The dam's primary functions are to create a reservoir, and to generate hydroelectric power. The reservoir behind the dam is called Lake Havasu and can store . The dam straddles the Arizona-California state border at the narrows the river passes through between the Whipple Mountains in San Bernardino County, California and the Buckskin Mountains in La Paz County, Arizona. Power generation The power plant has four Francis turbines with a combined capacity of 120 MW. Each turbine weighs . The head is . It produces electricity at 97 percent efficiency. Half of the electricity the plant produces is used by the Metropolitan Water District to pump water along the Colorado River Aqueduct, and the rest is sold to utilities in California, Arizona and Nevada. The generation of power is limited by a requirement to keep the water level of Lake Havasu between above sea level for proper operation of pumping plants for the Central Arizona Project and the Colorado River Aqueduct. Water supply Lake Havasu is the water source for the Colorado River Aqueduct. The aqueduct is operated by the Metropolitan Water District of Southern California, which supplies water to almost all cities in the greater Los Angeles, San Bernardino, and San Diego areas. The district paid for nearly the entire cost of the dam, but it is owned and operated by the U.S. Bureau of Reclamation. Lake Havasu is also the water source for the Central Arizona Project Aqueduct (CAP). The project is designed to provide water for irrigated agricultural areas, as well as municipal water for several Arizona communities, including the metropolitan areas of Phoenix and Tucson. Controversy Construction of the dam was a contentious issue for Arizona. Built as part of the larger Colorado River Compact of 1922, several political groups, their members and privately owned utility companies in Arizona were not pleased with the plan in general and