High Quality Content by WIKIPEDIA articles! The Columbia Basin Project (or CBP) in Central Washington, USA, is the irrigation network that the Grand Coulee Dam makes possible. It is the largest water reclamation project in the United States, supplying irrigation water to over 670,000 acres (2,700 km2) of the 1,100,000 acres (4,500 km2) large project area, all of which was originally intended to be supplied and is still classified as irrigable and open for the possible enlargement of the system. Water pumped from the Columbia River is carried over 331 miles (533 km) of main canals, stored in a number of reservoirs, then fed into 1,339 miles (2,155 km) of lateral irrigation canals, and out into 3,500 miles (5,600 km) of drains and wasteways.