Sinews of power from the controlled Columbia River at Grand Coulee Dam help turn the wheels of northwestern industry and lift the river's waters to the Grand Coulee above, from where they flow onto the parched lands of the Columbia Basin. This hydroelectric power and water, combined with the human and financial resources of the settlers, is turning a barren land into an economically substantial region.
Grand Coulee Dam and the Columbia Basin Irrigation Project have been hailed by the American Society of Civil Engineers as one of the seven engineering wonders of the United States. Together, they represent one of the greatest projects undertaken by man in his constant effort to make the world a better place in which to live.
Standing astride the mighty Columbia River like a Colossus of the new world, Grand Coulee Dam is a giant in a land of superlatives. Only after touring the installation and studying it from all angles does a realization of its bigness begin to dawn.
It is the largest concrete dam in the world, containing 10,585,000 cubic yards, or 21,154,000 tons, of concrete. It towers 550 feet from bedrock to the crest and tapers from a width of more than 450 feet at its base to 30 feet at its top.
The dam reaches as high as the Washington Monument and contains enough material to build 275 monuments of the same size. Its immensity dwarfs the 2 powerhouses at its base, each of which is as tall as a 13-story office building. There is enough concrete in the dam to build a standard two-lane concrete highway 22 feet wide and 8 inches thick from Seattle to Miami, with a 3-foot sidewalk for pedestrians.
Seen from a car or the window of the tour center, Grand Coulee Dam is indeed impressive, but it becomes even more awesome as one inspects its interior. Here the visitor is soon impressed with the fact that there is a great deal more to building a dam than merely placing a block of concrete in the path of a river. The designers of Grand Coulee Dam had to solve an almost infinite number of problems, and the final design was the sum of experience and knowledge gained by the science of engineering down through the centuries.
Undoubtedly one of the most eye- and ear-catching features of the dam is the waterfall, which pours over the face of the dam during the summer. The overflow begins in the latter part of May and continues through August and occasionally into September, creating a waterfall more than half as wide as Niagara Falls. At the peak of the high water flow in a normal year, 135 million gallons of water a minute cascade over the spillway and through the gates of the dam and plunge twice as far as the Niagara River at Niagara Falls. At night the whole of this frothing curtain of water is illuminated by alternating colored lights.
While the sight of thousands of tons of spilling water is thrilling and awesome, this is actually energy going to waste. One of the most important jobs of the dam is accomplished by the unseen torrents rushing through the turbines of the hydroelectric plants. In 1963 Grand Coulee Dam produced 12 billion kilowatt-hours of electricity.
In every 24-hour period at Grand Coulee there are periods of "high" and "low" power demand which reflect the dining, reading, working, television-viewing, and eating habits of a large portion of the people and industry of the Northwest.
The efficient operation of the hydroelectric plants at the dam to meet these power demands calls for a continuous flow of water to the generating units and sufficient "head" or depth of water in the reservoir behind the dam to turn the generating units. However, the Columbia River fluctuates a great deal from peak flow during the summer snowmelt to a low during the winter months, and the operation of the dam must be carefully planned to regulate water use and reservoir capacity in order to reap the greatest benefit from the river's power.
In the winter months water stored in the reservoir is used for power generation at Grand Coulee and at the downstream dams below Grand Coulee which have comparatively small storage reservoirs. In the spring when the Columbia River begins its annual rise, 80 feet of empty storage depth in the reservoir is available for use as a safety valve to partially absorb the force of potential spring floods. This flood-control operation of Grand Coulee has prevented a great deal of downstream property damage.
Circumstances have played no small part in the successful scheduling of Grand Coulee's workload. At about the time that the river starts its annual spring rise, the irrigation season begins. When the 6 powerful irrigation pumps just above the west end of the dam are operating, almost 10 percent of the average flow of the river is lifted over the rim of the river canyon wall 280 feet above the dam and begins its journey to the land and the crops of the irrigated portion of the project. Because of the higher water flow and consequently greater head in the reservoir at this time, there is surplus power available to operate the 6 irrigation pumps that handle this tremendous lifting job. Each of these pumps is powered by a 65,000-horsepower motor and will lift 1,600 cubic feet of water a second, or 720,000 gallons a minute. It is estimated that these 6 pumps could provide enough water in 3 minutes to fill a glass of water for every man, woman, and child in the United States. By the time the irrigation project is completed, there will be a total of 12 of these pumps.
This, then, is the Grand Coulee Dam. Structurally, it may be looked upon as a testimonial to its builders as a job well done and a monument to the wisdom of those farsighted persons whose persistence in their beliefs made this development possible. Functionally, it performs well the tasks for which it was designedprincipally, to provide water for the Columbia Basin Irrigation Project, and power for the people and industry of the Northwest.
Last Updated: 01-Feb-2008