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The Condition of Illinois Water Resources 2000

Surface Water Quality Monitoring

The Illinois EPA has maintained a comprehensive surface water monitoring and assessment program since its inception in 1970. Changes and additions to the monitoring effort have been undertaken to keep pace with technological advances and broadening environmental concerns. Surface water monitoring activities focus on water and sediment chemistry as well as on physical and biological data (aquatic invertebrates, fish, and habitat). As a result of these monitoring programs, data from approximately 3,400 stations have been utilized in the assessment of surface water quality conditions. Data from these stations are utilized to make either "monitored" or "evaluated" resource assessments. "Monitored" assessments are based on data collected by Illinois EPA or other professional staff that is five years old or less. "Evaluated" assessments are based on volunteer collected data or monitored data that is more than five years old.

The Illinois EPA conducts a wide variety of water quality monitoring programs. Among these programs are the Ambient Water Quality Monitoring Network, Intensive River Basin Survey (in cooperation with the Illinois Department of Natural Resources), Facility-Related Stream Survey, Ambient Lake Monitoring Program, Clean Lakes Program Intensive, Volunteer (Citizen) Lake Monitoring Program, and the National Nonpoint Source Monitoring Program.

The objectives of these monitoring and assessment programs are to:

  • Analyze and interpret data/information to evaluate attainment of designated uses (aquatic life, drinking water, fish consumption, recreation, etc.);
  • Determine long-term trends in physical, chemical, and biological conditions;
  • Identify water quality problems and problem areas and further investigate the extent and cause(s) of the problems; and
  • Provide a measure of the effectiveness of Illinois' water pollution control programs

The Illinois EPA's water quality program is designed to evaluate and protect water resource "designated uses." Designated uses take into consideration the use and value of the waterbody for public water supply; for propagation of fish, shellfish, and wildlife; and for recreational, agricultural, industrial and navigational purposes. In Illinois, waterbodies have been classified for a variety of designated uses that include: general use, public and food processing water supplies, secondary contact, and indigenous aquatic life. Lake Michigan has its own designated uses based upon a set of more stringent water quality standards. Water quality conditions are described in terms of the degree to which a waterbody attains its designated uses.

For this 2000 report and the 33 water quality fact sheets, water quality is rated as either "good," "fair," or "poor" based on physical, chemical, and biological data collected through 1998. A "good" rating means a river or lake meets the needs of all designated uses. "Fair" means water quality has been impaired and the waterbody meets some, but not all, of its designated uses. A waterbody that is rated as "poor" has water quality that has been severely impaired and cannot support designated uses to any degree.

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