In accordance with Sections 305(b) and 303(d) of the Federal Clean
Water Act (CWA), the Illinois EPA must report to the USEPA on the quality
of Illinois surface water (e.g., lakes, streams, Lake Michigan, wetlands)
and groundwater resources (Section 305b) and provide a list of those
waters where their designated uses are deemed "impaired" (Section
303d). In addition, the Illinois EPA must assess the water quality of
all publicly-owned lakes in accordance with section 314(a)(1). To aid
in making these determinations, the Illinois EPA annually collects chemical,
physical, biological, habitat, and toxicity data, depending on the type
of water body. Data collected from outside sources may also be considered
during this process.
Resource quality conditions are assessed in terms of the degree to
which waters attain "beneficial uses", also called "designated
uses". Pollution control programs are designed to protect designated
individual uses, including aquatic life, indigenous aquatic life, primary
contact (swimming), public and food processing water supply (drinking
water), secondary contact, aesthetic quality, and fish consumption.
Each state has the responsibility to set water quality standards that
protects these uses. In Illinois, the Illinois Pollution Control Board
is the regulatory body responsible for establishing water quality standards.
Results of more recent statewide assessments can be found in
the following "Integrated Water Quality Report and Section
303d List" documents and Illinois Water Quality Mapping
Tool. Previous assessments can be found in "Illinois Water
Quality Reports" and associated "Condition of Illinois
Water Resources" reports.