The Illinois River, the most significant river in Illinois, drains nearly half of the state and most of the major streams in Illinois drain into it. The Illinois Waterway with its system of locks and dams links Chicago and the Great Lakes to the Mississippi River, and, thus, the Gulf of Mexico. This linkage has a significant transportation and commercial value for the state and the nation. In addition, with its numerous backwater lakes, wetlands, and floodplain forests, the Illinois River valley provides a significant habitat for fish, waterfowl, birds, and other animals, making it an important ecological resource. The Illinois River’s environment has been subjected to many of the impacts associated with developments in the watershed, including waste discharges from urban areas, water-level control for navigation, and sediment and chemical inflow from agricultural lands. The quality of the river was severely degraded for several decades prior to the 1970s when environmental regulations were enacted to control pollutant discharges. Since then the quality of the river has been gradually improving. However, problems associated with erosion and sedimentation have not been improving and are recognized as the number-one environmental problem in the Illinois River valley. The main sources of sediment to the Illinois River valley are watershed erosion, streambank erosion, and bluff erosion. The contribution of watershed erosion to the sedimentation problem in the Illinois River valley has been quantified by analyzing the sediment yields of tributary streams that drain into the valley. Annual sediment yield equations were developed for the major tributaries and then used to construct an approximate sediment budget for the Illinois River valley. The Illinois River, the most significant river in Illinois, the drains nearly half of the state and most of the major streams in Illinois drain into it. The Illinois Waterway with its system of locks and dams links Chicago and the Great Lakes to the Mississippi River, This and has the significant backhoe lakes, wetlands, and floodplain forests, the Illinois River valley provides a significant habitat for fish , waterfowl, birds, and other animals, making it an important ecological resource. The Illinois River’s environment has been subjected to many of the impacts associated developments with the watershed, including waste discharges from urban areas, water-level control for navigation, and sediment and chemical inflow from agricultural lands. The quality of the river was severely degraded for several or earlier prior to the 1970s when environmental regulations Since then the quality of the river has been improving. However, problems associated with erosion and sedimentation have not been improving and are recognized as the number-one environmental problem in the Illinois River valley. The main sources of sediment to the Illinois River valley are watershed erosion, streambank erosion, and bluff erosion. The contribution of watershed erosion to the sedimentation problem in the Illinois River valley has been quantified by analyzing the sedimentation yields of tributary streams that drain into the valley. sediment yield equations were developed for the major tributaries and then used to construct an approximate sediment budget for the Illinois River valley.