Section 305(b) of the Clean Water Act (CWA) requires the Indiana Department of Environmental Management (IDEM) to assess and report on whether Indiana waters support the beneficial uses designated in Indiana’s water quality standards. IDEM’s CWA Section 305(b) assessments are made in accordance with IDEM’s Consolidated Assessment and Listing Methodology (CALM) by comparing existing and readily available water quality data to the applicable water quality criteria in the State’s water quality standards.
The majority of the data IDEM uses in its 305(b) assessments are collected by IDEM staff using a rotating basin approach. IDEM has divided Indiana into nine major water management basins and monitors one major basin each year. IDEM staff assess the data collected in each basin the following year.
In addition to agency-collected data, IDEM solicits data through its External Data Framework from external organizations and agencies, including the United States Geological Survey, Indiana University’s School of Public and Environmental Affairs, and the Indiana State Department of Health. IDEM also solicits water quality data from other colleges, universities, and local organizations, such as county health departments, watershed management groups and cities and towns. OWQ’s Integrated Reporting Program solicits data for its 305(b) assessment and 303(d) listing processes every two years.
| Basins | Water Quality Data Assessed for the Basin | Results Published in Indiana's Integrated Report and 303(d) List | Indiana’s Major River Basins |
|---|---|---|---|
| Ohio River Tributaries | 2020 | 2022 |  Click to Enlarge |
| White River, West Fork Basin | 2021 | ||
| Patoka River Basin | 2022 | 2024 | |
| White River, East Fork Basin | 2023 | ||
| Great Miami River Basin (Whitewater River) | 2024 | 2026 | |
| Upper Wabash River Basin | 2025 | ||
| Lower Wabash River Basin | 2026 | 2028 | |
| Upper Illinois River Basin | 2027 | ||
| Great Lakes Basin | 2028 | 2030 |
IDEM’s water quality assessment results are reported to the United States Environmental Protection Agency (U.S. EPA) every two years through the Indiana Integrated Water Monitoring and Assessment Report, which describes the condition of Indiana’s lakes, streams, ground water and its Lake Michigan shoreline.
Indiana’s 2024 Integrated Water Monitoring and Assessment Report
IDEM published the notice of public comment period for its draft 303(d) List of Impaired Waters, in the Indiana Register on February 1, 2024, formally opening the 45-day public comment period. IDEM received several public and U.S. EPA comments on the draft 2024 303(d) list and the Consolidated Assessment and Listing Methodology (CALM) used to develop the 303(d) list prior to the close of the public comment period on March 18, 2024.
IDEM uploaded its 2024 Integrated Report, including the finalized 2024 303(d) List of Impaired Waters to U.S. EPA’s Assessment and Total Maximum Daily Load Tracking and Implementation System (ATTAINS) online on March 29, 2024.
The 2024 303(d) List of Impaired Waters was presented to the Indiana Environmental Rules Board in a public meeting on April 10, 2024.
IDEM’s 2024 Integrated Water Monitoring and Assessment Report Submittal, Including the 2024 303(d) List of Impaired Waters
- Indiana's 2024 Integrated Water Monitoring and Assessment Report to the U.S. EPA [PDF]
- Appendix A: Integrated Report Tables [PDF]
- Appendix B: Integrated Report Figures [PDF]
- Appendix C: Metadata and Definitions [PDF]
- Appendix D: Status of Category 4 Waters [PDF]
- Appendix E: IDEM’s Priority Ranking and 2024-2026 Schedule for Total Maximum Daily Load Development [PDF]
- Appendix F: IDEM’s 305(b)/303(d) Monitoring, Assessment, Reporting, and Listing Schedule [PDF]
- Appendix G: IDEM’s 2024 Consolidated Assessment and Listing Methodology [PDF]
- Appendix H: Comprehensive Aquatic Life Use and Recreational Use Assessments [PDF]
- Appendix I: Trend and Trophic Status of Indiana’s Lakes
- Appendix J: IDEM’s Notice of Comment Period for the 2024 Draft 303(d) List [PDF]
- Appendix K: IDEM’s Responses to Comments on the Indiana Draft 2024 303(d) List of Impaired Waterbodies and Consolidated Assessment and Listing Methodology (CALM) [PDF]
- Appendix L: Listing Tables Including Indiana’s Finalized 303(d) List of Impaired Waters (Category 5) for 2024 [XLS]
- Appendix M: Indiana’s 2024 Consolidated List (Categories 1-5) [XLS]
General information on the 303(d) list is available on the Section 303(d) List Frequently Asked Questions page. You may also contact the Integrated Report Coordinator with any questions regarding the 303(d) list or to obtain files for previous listing cycles.