Water Quality in the Lower Illinois River Basin, Illinois, 1995–98

By George E. Groschen, Mitchell A. Harris, Robin B. King, Paul J. Terrio, and Kelly L. Warner

U.S. GEOLOGICAL SURVEY CIRCULAR 1209

The full report is available in pdf.  Links to the pdf.

A contribution of the National Water-Quality Assessment (NAWQA) Program

• NATIONAL WATER-QUALITY ASSESSMENT PROGRAM
• SUMMARY OF MAJOR FINDINGS
  • Stream and river highlights
  • Ground-water highlights
• INTRODUCTION TO THE LOWER ILLINOIS RIVER BASIN
  • Land use
  • Study design in relation to land use
  • Water use
  • Hydrologic conditions during the study period
  • The lower Illinois River
• MAJOR FINDINGS
  • Nutrient concentrations in streams and rivers are a major concern
  • Stream and river samples often exceeded the nitrate drinking-water standard and phosphorus guideline
  • Nitrate concentrations were lower than in other areas of the Corn Belt during late summer
  • Nitrate concentrations differed upstream and downstream from water-supply reservoirs
  • NATIONAL PERSPECTIVE—Algal index indicates comparatively poor water quality in corn belt
  • Riparian buffer zones influence the quality of Midwestern streams and rivers
  • NATIONAL PERSPECTIVE—Nutrient concentrations were among the highest in the Nation
  • Nitrate concentrations in some shallow wells exceeded the drinking-water standard
  • Some pesticides were always detected in streams and rivers
  • Pesticide concentrations in streams periodically exceeded drinking-water standards
  • Pesticide concentrations in streams have a seasonal pattern
  • Many factors affect the presence and concentration of pesticides in streams
  • Concentrations of agricultural chemicals generally reflect application rates
  • Stream size affects pesticide concentrations
  • Concentrations of alachlor and cyanazine in the Illinois River decreased
  • Pesticide breakdown products were detected more frequently than the parent compound
  • Pesticides were not frequently detected in ground water
  • Insecticides discontinued in the 1970s were still detected in fish and sediment
  • NATIONAL PERSPECTIVE—Basin and national results were similar for pesticides
  • Other organochlorine compounds are persistent in sediments and fish
  • Common stream animals indicate poor water-quality conditions
  • Highest concentrations of polycyclic aromatic hydrocarbons were in bed sediment near urban areas
  • Arsenic exceeded the drinking-water standard in the Mahomet aquifer
  • NATIONAL PERSPECTIVE—Arsenic in ground water is a national concern
  • Radon exceeded the proposed drinking-water standard in almost one-half of shallow wells
  • Volatile organic compounds were detected in ground water at low concentrations
  • Fish and sediment in the Illinois River have high concentrations of trace elements
• STUDY UNIT DESIGN
• APPENDIX—WATER-QUALITY FROM THE LOWER ILLINOIS RIVER BASIN IN A NATIONAL CONTEXT
• References
• A Coordinated Effort
• Glossary