Initial water quality planning efforts documented that agriculture activities are a major source of pollution in Illinois. The most severe agricultural related problem is soil erosion resulting in sedimentation. In Illinois, estimated gross erosion exceeds 180 million tons annually, with 88 percent from cropland. Illinois Environmental Protection Agency in cooperation with various U.S. Department of Agriculture agencies evaluated the water quality impacts of resource managment system implementation under the ACP Special Water Quality Project in the Blue Creek Watershed. The physical, biological, and chemical characteristics of the Blue Creek Watershed Lake have been studied since 1979. A comprehensive monitoring network for the entire Blue Creek Watershed was established to document the basic hydroiogical, meteroiogical, and water quality factors of the project area during 1980. The duration, timing and quantity of nonpoint source pollutants were evaluated within the watershed. The monitoring program was designed to link water quality to what is happening on the land. To understand the processes of soil erosion and nutrient/sediment transport and to draw meaningful conclusions about land use effects, focus was given to sources and movement from sources to the lake outlet. This evaluation integrated reservoir sedimentation surveys, lake water quality monitoring, biological monitoring, water quality monitoring at stream gauging stations and small field sites, a channel dynamics study, and a computerized gross erosion estimate. The stream gauging station and field site monitoring were event-oriented sampling to supplement the baseline monitoring on the stream network and in the lake. There were obvious seasonal and spatial trends exhibited by several physical and chemical parameters within the lake and watershed. In Illinois, erosion control is being used as a surrogate for sediment control because sediment control is less amenable to quantitative analysis. This reflects the current lack of knowledge concerning sediment origin, transport, deposition, and control technology. Integration of source and sediment budget studies with realistic concepts of storm runoff production results from this project will clarify some aspects of the interrelationships between gross erosion and water quality impacts.