USGS Publications Warehouse

Abstract

Median suspended-sediment concentrations ranged from 100 to 110 milligrams per liter for 3 stations on the Kansas River and from 4 to 110 milligrams per liter for 10 stations on tributary streams during May 1987 through April 1990. For tributary stream stations upstream from large reservoirs, concen- trations in the 90th percentile ranged from 240 to 3,200 milligrams per liter. The larger median and 90th-percentile concentrations were associated with high-density irrigated cropland with gradual slopes and nonirrigated cropland with steeper slopes. Smaller median and 90th-percentile concentrations upstream from reservoirs were from areas of little or no row-crop cultivation or areas of substantially less-than-normal precipitation and streamflow. Suspended-sediment concentrations followed a con- sistent seasonal pattern; after accounting for the effect of flow, concentrations were typically smallest during January-February and largest during July-August. Mean annual suspended-sediment transport in the Kansas River from May 1987 through April 1990 increased in the downstream direction from 1,700,000 to 4,100,000 tons per year. Suspended-sediment yields for tributary streams ranged from 17 to 260 tons per square mile per year. Because of abnormal climatic conditions and other factors, no conclusions could be reached con- cerning relations of suspended-sediment transport or yield to natural or human factors. Only one upward and one downward trend in flow-adjusted, suspended-sediment concentrations were statistically significant. The trend-test results could not be explained by data on cropland removed from production or the effect of detention structures.