The U.S. Geological Survey began full-scale implementation of the National Water-Quality Assessment (NAWQA) Program in 1991. The purposes of NAWQA are to describe the status and trends in the quality of the Nation's water resources and aquatic ecosystems, and to determine factors affecting water quality at local, regional, and national scales. The Upper Mississippi River (UMIS) NAWQA study unit, which includes all of the surface drainage to the Mississippi River Basin upstream from Lake Pepin, encompasses 47,000 mi2. The study characterizes the geographic and seasonal distribution of water quality and aquatic biota in relation to anthropogenic activities and natural features. The initial phase of the UMIS study, during 1994-99, is focused on an area in Minnesota and Wisconsin that includes the seven-county Twin Cities (Minneapolis and St. Paul) metropolitan area. This report summarizes selected sources of information that are being used to aid in understanding water-quality issues and processes that form the basis of the sampling design for the study. This literature review includes sources of information about surface-and groundwater hydrology, water quality, and aquatic biology and ecology. the sampling design for the study. Water quality in the study unit is affected by natural and anthropogenic factors. Natural factors include climate, physiography, geology, soils, topography, vegetation and aquatic biology. Anthropogenic factors include hydrologic modification, point-and nonpoint-source contaminant discharges, and changes to land use and to land cover. Water-quality issues of local importance, and important to the program at a national level, have been defined by the study's liaison committee composed of representatives from Federal, state, and local agencies, private industry, and by NAWQA Program leadership. These issues have guided the literature review. Important sources of information include the Metropolitan Council Environmental Services,
