Columbia Basin Project

Grand Coulee Dam Construction

Grand Coulee Dam is one of the largest concrete structures in the world, containing nearly 12 million cubic yards of concrete. That's enough to build a sidewalk four feet wide and four inches thick and wrap it twice around the equator (50,000 miles), or if you'd rather, build a highway from Seattle to Miami!


In the first decade of the 20th century, settlers, having acquired land under homesteading laws, flooded into eastern Washington to try their luck at dryland farming. However, because the average annual rainfall was less than 10 inches, farms failed, and many farmers lost their land. Irrigation was needed to make a go of farming, but through the years numerous small irrigation schemes were unsuccessful.

However, in 1918 a plan was developed to irrigate the Columbia Basin by raising water from the deep canyon of the Columbia River onto the plateau by means of a dam at the Grand Coulee. Construction of Grand Coulee Dam began in 1933 and was completed in 1942. But it was almost a decade later—1951—before the first irrigation water began flowing, forever changing the landscape.

Water is stored in Lake Roosevelt behind Grand Coulee Dam and diverted into storage reservoirs (Banks and Billy Clapp Lakes) that supply an extensive system of canals to other reservoirs. Potholes Reservoir, just north of the refuge, receives irrigation water from Grand Coulee Dam, as well as irrigation water already used and drained from farmland upslope; the water is then recycled for use a second time. O'Sullivan Dam holds back Potholes Reservoir, which covers an area of 45 square miles. This earthfill dam in the center of the Columbia Basin is 3.5 miles long and rises 200 feet above bedrock. Water leaves Potholes Reservoir, flows to Scootney Reservoir south of Othello, and joins a canal delivering water to thirsty lands just north of Pasco. Another canal leaves Potholes Reservoir to serve farmers on the Wahluke Slope that abuts the Columbia River.

Today, the Columbia Basin Project is the largest water reclamation project in the United States, providing irrigation water to 671,000 acres and generating 6,809 megawatts of hydropower.

Agriculture flourishes because of the abundance of water, fertile soils, sunshine and the 280-day growing season. Major crops include apples, potatoes, alfalfa, corn, peas, onions, mint, grapes and grains.

But the Columbia Basin Project "leaks." As a result, new lakes and ponds formed from leakage from the project and from elevated water tables from unused irrigation water seeping into the ground. With this new water came waterfowl and shorebird species that previously had found no sanctuary in this dry environment. The area is now a major spring stopover for lesser Sandhill cranes and winter habitat for numerous species of waterfowl. However, with change also came loss. As sagebrush was removed to make way for crops, wildlife that depended upon the sagebrush ecosystem had to find other homes.