Hoover Dam, in Blendon Township, near Westerville, Ohio, dams the Big Walnut Creek to form the Hoover Memorial Reservoir. This reservoir is a major water source for the city of Columbus, Ohio. It holds 20.8 billion US gallons (79,000,000 m³) of water and has a surface area of 3,272 acres (13.24 km²), or about five square miles. Construction began during 1953 due to the increased water demand of post-war Columbus. The project was completed and dedicated in 1955 and the dam officially opened in 1958. It was named for two brothers, Charles P. Hoover and Clarence B.