page_title: Columbia Basin Project
section_title: Geology
hierarchical_section_title: Columbia Basin Project / Geology
caption_attribution_description: English: Drumheller Channels; East edge of the Royal Slope in the Columbia Valley south of the Pot Holes Reservoir by 10 miles; the lake I believe is Black Lake.
context_page_description: The Columbia Basin Project in Central Washington, United States, is the irrigation network that the Grand Coulee Dam makes possible. It is the largest water reclamation project in the United States, supplying irrigation water to over 670,000 acres of the 1,100,000 acres large project area, all of which was originally intended to be supplied and is still classified as irrigable and open for the possible enlargement of the system. Water pumped from the Columbia River is carried over 331 miles of main canals, stored in a number of reservoirs, then fed into 1,339 miles of lateral irrigation canals, and out into 3,500 miles of drains and wasteways. The Grand Coulee Dam, powerplant, and various other parts of the CBP are operated by the Bureau of Reclamation. There are three irrigation districts in the project area, which operate additional local facilities.
context_section_description: The Columbia Basin in Central Washington is fertile due to its loess soils, but large portions are a near desert, receiving less than ten inches (254 mm) of rain per year. The area is characterized by huge deposits of flood basalt, thousands of feet thick in places, laid down over a period of approximately 11 million years, during the Miocene epoch. These flood basalts are exposed in some places, while in others they are covered with thick layers of loess.
  During the last ice age glaciers shaped the landscape of the Columbia River Plateau. Ice blocked the Columbia River near the north end of Grand Coulee, creating glacial lakes Columbia and Spokane.  Ice age glaciers also created Glacial Lake Missoula, in what is now Montana.  Erosion allowed glacial Lake Columbia to begin to drain into what became Grand Coulee, which was fully created when glacial Lake Missoula along with glacial Lake Columbia catastrophically emptied. This flood event was one of several known as the Missoula Floods. Unique erosion features, called channeled scablands, are attributed to these amazing floods.
caption: Drumheller Channels, 10 miles (16 km) south of Potholes Reservoir, are examples of channeled scablands
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