This report presents the results of a reconnaissance evaluation of the fluvial-sediment transport by streams in the 28,000-square-mile upper Columbia River basin in eastern Washington. The basin ranges in altitude from about 340 to 9,000 feet, and receives annual precipitation ranging from more than 150 inches in the mountains to less than 10 inches at the lower altitudes. A good vegetative cover is sustained in the mountains by the high precipitation, whereas vegetation is sparse in the lower semiarid parts of the basin.
In the mountainous areas snowmelt runoff transports most of the sediment during April through June. In the semiarid parts of the basin, little runoff occurs during most years, and most of the sediment is transported when heavy, warm rains fall on extensive accumulations of snow. During the 1970 and 1971 water years, the measured suspended-sediment concentrations in the upper Columbia River basin ranged from less than 1 milligram per liter in many streams to more than 200,000 milligrams per liter in Providence Coulee. The estimated long-term annual suspended-sediment yields range from less than 10 tons per square mile in many basins to more than 500 tons per square mile in Providence Coulee.
Man's activities have caused only a slight increase in the magnitude of the sediment discharge to the Columbia River. Although cultivation has initiated a large increase in erosion on the Columbia Plateau, and winds there move some of the loosened or easily eroded soils to depressions and runoff channels, sediment transport by streams has not increased greatly. This is because the little surface runoff on the plateau does not transport the soils to streams and to the Columbia River.
|Title||Sediment transport by streams in the Upper Columbia River Basin, Washington, May 1969-June 1971|
|Authors||Leonard M. Nelson|
|Publication Subtype||USGS Numbered Series|
|Series Title||Water-Resources Investigations Report|
|Record Source||USGS Publications Warehouse|