Columbia Basin Project - Irrigation of The Columbia Basin

Irrigation of The Columbia Basin

When it was built, Grand Coulee Dam was the largest dam in the world, but it was only part of the irrigation project. Additional dams were built at the north and south ends of Grand Coulee, the dry canyon south of Grand Coulee Dam, allowing the coulee to be filled with water pumped up from the Columbia River. The resulting reservoir, called Banks Lake, is about 30 miles (48 km) long. Banks Lake serves as the CBP's initial storage reservoir. Additional canals, siphons, and reservoirs were built south of Bank Lake, reaching over 100 miles (160 km). Water is lifted 280 feet (85 m) from Lake Roosevelt to feed the massive network.

Two and three percent of the Columbia's flow is currently diverted at the Grand Coulee Dam. The amount of water annually diverted into the CBP and used for irrigation is larger than the entire annual flow of the Colorado River. There are plans to double the area of irrigated land, according to tour guides at the dam, over the next several decades. However, the Bureau of Reclamation website states that no further development is anticipated, with 671,000 acres (2,720 km2) irrigated out of the original 1,100,000 acres (4,500 km2) planned.

Interest in completing the Columbia Basin Project's 1,100,000 acres (4,500 km2) has grown in the late 20th and early 21st centuries. One reason for the renewed interest is the substantial depletion of the Odessa aquifer. Agricultural operations within the CBP's boundaries but outside the developed portion have for decades used groundwater pumped from the Odessa aquifer to irrigate crops.