An aerial view of Grand Coulee Dam. © Alison M. Jones
World’s Most Dammed River
By Kalista Pruden, Lake Windermere Project
(Reprinted from The Invermere Valley Echo, August 20, 2008)
THE Columbia River system is the most heavily dammed river system in the world. There are over 450 dams in the Columbia River Basin, most of which were built to produce hydroelectricity. Dams are also built to regulate flows by crating reservoirs that provide water storage and flood control.
The Columbia River Basin, at 671,000 square kilometres, is the fourth largest river basin in North America. With 10 major tributaries (the Kootenay, Okanagan, Wenatchee, Spokane, Yakima, Snake, Deschutes, Willamette, Cowlitz, and Lewis rivers), the Columbia River’s annual average discharge is 160 million acre-feet of water. By water volume, the Columbia is second only to the mississippi as the largest river in North America.
In addition, the Columbia River falls 2,650 vertical feet (half of which are in Canada) from beginning to end. This makes it the most powerful river in North America as hydropower capability of a river is measured by multiplying flow by change in elevation. Based on this equation, the Columbia River’s generating capacity is more than 21 million kilowatts.
At a total length of 1.900 kilometres, the Columbia is the 15th longest river in North America, emptying into the Pacific Ocean at Astoria, Oregon. Columbia and Windermere Lakes are the headwaters of the Columbia River, a vast river fed by a drainage basin that encompasses one Canadian province (British Columbia) and seven American states (Washington, Idaho, Oregon, Montana, Nevada, Wyoming, and Utah). The Columbia River Basin consists of diverse ecology, ranging from temperate rain forests to semi-arid plateaus with precipitation levels from 280 centimeters to 15 centimeters per year.
Although only 15% of the Columbia River Basin is located in Canada, 40% of the total runoff for the river originates north of the border. This is because w get far more snow than our neighbors to the south. Approximately 80% of North America’s water resources come from snow-melt; the Columbia River being no exception.
As a snow-charged river, the Columbia fluctuates seasonally in volume. The river experiences highest flows between April and September and lowest flows between December and February. With over 15 million Columbia River users, it is no wonder that winter water storage and spring flooding issues warranted the construction of reservoirs.
There are 14 dams on the main stem of the Columbia River, and hundreds of other major and minor structures in its watershed that regulate flows. The first major dam built on the Columbia River for producing hydroelectricity is the Rock Island Dam. Completed in 1933, the Rock Island Dam is now small in comparison to the behemoths of Bonneville and Grand Coulee, completed by the U.S. federal government in 1938 and 1941 respectively.
There are 12 dams operated by BC Hydro within the Canadian portion of the Columbia River Basin, four of which are main stem dams (Revelstoke, Mica, Hugh Keenleyside and Duncan). Completed in 1983, the Revelstoke Dam was the last of the main stem dams constructed on the Columbia River.
Wildsight’s Columbia Headwaters program works to protect biodiversity and healthy human communities in the upper Columbia River Valley.
For more information, contact Wildsight’s Lake Windermere Project office at 250-341-6989, located beside the Invermere Community Centre. The Lake Windermere Project is a long-term comprehensive stewardship program dedicated to safeguarding the health of our lake.