The upper Illinois River Basin (UIRB) is the 10,949 square mile drainage area upstream from Ottawa, Illinois, on the Illinois River. The UIRB is one of 13 studies that began in 1996 as part of the U.S. Geological Survey’s National WaterQuality Assessment program. A compilation of environmental data from Federal, State, and local agencies provides a description of the environmental setting of the UIRB. Environmental data include natural factors such as bedrock geology, physiography and surficial geology, soils, vegetation, climate, and ecoregions; and human factors such as land use, urbanization trends, and population change. Characterization of the environmental setting is useful for understanding the physical, chemical,...
