Annually, about 2.5 million acre feet (or over 814 billion gallons) of water is pumped from Lake Roosevelt into Banks Lake to support irrigation.

Generally, these water diversions occur between March and October. Via canals and other means, water from Lake Roosevelt irrigates about 670,000 acres of land. Combined with the naturally rolling countryside, nourishing and drainable soil, a long growing season, and breezes strong enough and frequent enough to minimize frost pockets, the result is one of the world’s most bountiful croplands. A map of the irrigable lands shows that they reach as far south as the Tri-Cities and irrigate lands in four different counties.

Without irrigation, this bounty would not be possible. Farmers and ranchers could not sustain operations with, at best, six inches of rainfall that mostly fall before the summer growing season. Before irrigation was introduced, lack of rain combined with the searing heat of the high desert environment drove people with the best of intentions from the land they came to till.

With irrigation, which officially began in 1948, about 6,000 farms sustain more than 60 crops. Diversity extends from potatoes to peppermint, with the largest crops including over 260 million pounds of apples and about 20 million bushels of wheat and corn. In addition, there is dairy farming and 200,000 beef cattle. Annually, the Columbia Basin Project farms earn about 630 million dollars from their crops.

Irrigation water is pumped from Lake Roosevelt by the Grand Coulee Pump-Generating Plant. Here, 12 huge pumps lift the water up 280 feet into Banks Lake, which is a 27-mile-long reservoir that extends south to the town of Coulee City. A main canal then takes the water to three large canals that extend a total of 333 miles and serve as main arteries to laterals. Almost 2000 miles of laterals carry water to croplands for irrigation.