Trends in Suspended-sediment Concentration at Selected Stream Sites in Kansas, 1970–2002 Water-resources Investigations Report 03–4150 12. Graphs Showing Relations between Discharge and Suspended-sediment Concentration and Turbidity and Suspended-sediment Concentration for Two Sediment Sampling 13. 

Knowledge of erosion, transport, and deposition of sediment relative to streams and impoundments is important to those involved directly or indirectly in the devel opment and management of water resources. Monitoring the quantity of sediment in streams and impoundments is important because: (1) sediment may degrade the water quality of streams for such uses as municipal water supply, (2) sediment is detrimental to the health of some species of aquatic animals and plants, and (3) accumulation of sediment in water-supply impoundments decreases the amount of storage and, therefore, water available for users. One of the objectives of the Kansas Water Plan is to reduce the amount of sediment in Kansas streams by 2010. During the last 30 years, millions of dollars have been spent in Kansas watersheds to reduce sediment transport to streams. Because the last evaluation of trends in suspended-sediment concentrations in Kansas was completed in 1985, 14 sediment sampling sites that represent 10 of the 12 major river basins in Kansas were reestablished in 2000. The purpose of this report is to present the results of timetrend analyses at the reestablished sediment datacollection sites for th e period of about 1970–2002 and to evaluate changes in the watersheds that may explain the trends. Time-trend tests for 13 of 14 sediment sampling sites in Kansas fo r the period from about 1970 to 2002 indicated that 3 of the 13 sites tested had statistically significant decreasing suspende sediment concentrations; however, only 2 sites, Walnut River at Winfield and Elk River at Elk Falls, had trends that we re statistically significant at the 0.05 probability level. Increasing suspended-sediment concentrat ions were indicated at three sites although none we re statistically significant at the 0.05 probability level. Samples from five of the six sampling sites located upstream from reservoirs indica ted decreasing suspendedsediment concentrat ions. Watershed impoundments located in the respective river basins may contribute to the decreasing suspended-sedime trends exhibited at most of the sampling sites because the impoundments are designed to tra sediment. Both sites that exhibited statistically significant decreasing su pended-sediment concentrations have a larg e number of watershed impoundments located in their respective drainage basins. The relation between percentage o the watershed affected by impoundments and trend in suspended-sediment concentration for 11 sites indicated that , as the number of impound ments in the watershed increases, suspended-s ment concentration decr eases. Other conservation practices, such as terracing of farm fields and contour farming, also may contribute to the reduced suspended-sediment concentrations if their use has increased during the period of analysis. Regression models were developed for 13 o 14 sediment sampling site s in Kansas and can be used to estimate suspended-sediment concentr tion if the range in stream discharge for which they were developed is not exceeded and if time