How a Canal Irrigation System Works

How a canal irrigation system works
In 1948 the first waters from the Columbia Basin Project reached farms in the Pasco area. Since then more than 670,000 acres of farmland have been relying on hundreds of miles of canals that deliver the water. But how does it all work? We learned from the Bureau of Reclamation and local farmers how things work.

How does the water get from Lake Roosevelt to the Central Washington farmlands?
A pump generation plant near the Grand Coulee Dam drafts water out of Lake Roosevelt and pumps it 280 feet uphill through a feeder canal into the Banks Lake reservoir. From there, roughly 330 miles of major distribution canals and 1,900 miles of lateral and smaller canals serve more than 10,000 farms in the region.

Once the water gets close to the farms through the canals, how does it get to the farmer’s fields?
Hundreds of pump stations are placed throughout the area that help move the water from the canals into underground pipes. Those pipes then carry the water to a central location for the farm. At that junction, another pump and set of pipes feed water into the farmer’s irrigation system. Many farmers in the Columbia Basin use center pivot irrigation systems, often referred to as “circles.” When flying in an airplane from Seattle to Spokane, on a clear day you can see the circles within the farmland. The irrigation sprinklers are all set on a center pivot system that makes a circle when watering the crop.

Does the water from the system only get used once?
No, a lot of the water from this system gets used again before eventually returning to the Columbia River. Runoff is collected at the Potholes Reservoir and it re-enters the system, and drain water or waste way water also re-enters the system. According to the Bureau of Reclamation, “irrigators use about 2.5 million acre-feet of Columbia River water each year. Re-using water gives irrigators an additional one million acre-feet”