Section 305(b) of the Clean Water Act (CWA) requires the Indiana Department of Environmental Management (IDEM) to assess and report on whether state waters support the beneficial uses designated in Indiana’s water quality standards. IDEM’s CWA Section 305(b) assessments are made by comparing existing and readily available water quality data to applicable water quality criteria, following guidance in IDEM’s Consolidated Assessment and Listing Methodology (CALM). Water quality data collected through IDEM’s water monitoring programs are assessed and results are reported to the United States Environmental Protection Agency (U.S. EPA) through the biennial Indiana Integrated Water Monitoring and Assessment Report (IR), which describes the condition of Indiana’s lakes, reservoirs, streams, ground water, and Lake Michigan shoreline.
Most of the data IDEM uses in its 305(b) assessments are collected using a rotating basin approach in which Indiana is divided into nine major water management basins and IDEM staff monitor randomly selected sites in one major basin each year. IDEM also employs numerous targeted programs in which specific sites are monitored, allowing for a direct comparison of individual locations over time. IDEM staff analyze and assess the data collected from each basin the following year and assessment results for the previous two years are published in Indiana’s Integrated Report and 303(d) List of Impaired Waters.
| Basins | Water Quality Data Collected in the Basin | 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 | 2019 | 2020 | 2022 |  Click to Enlarge |
| White River, West Fork Basin | 2020 | 2021 | ||
| Patoka River Basin | 2021 | 2022 | 2024 | |
| White River, East Fork Basin | 2022 | 2023 | ||
| Great Miami River Basin (Whitewater River) | 2023 | 2024 | 2026 | |
| Upper Wabash River Basin | 2024 | 2025 | ||
| Lower Wabash River Basin | 2025 | 2026 | 2028 | |
| Upper Illinois River Basin | 2026 | 2027 | ||
| Great Lakes Basin | 2027 | 2028 | 2030 |
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, county health departments, watershed management groups, and municipalities. The solicitation period for the Indiana 2028 Integrated Report and 303(d) List is from November 2025 to October 2027 with any data submitted after this time eligible for consideration for the 2030 Integrated Report.
Indiana’s 2026 Integrated Water Monitoring and Assessment Report
On February 5, 2026, IDEM published a draft 2026 Section 303(d) List of Impaired Waters for Indiana and Consolidated Assessment and Listing Methodology (CALM) document on the IDEM Integrated Water Monitoring and Assessment Report and Section 303(d) List webpages for a 45-day public comment period. A notice directing the public to the draft 2026 303(d) list and CALM was posted in the Indiana Register on February 25, 2026. The public comment period ended on March 21, 2026, and IDEM received numerous comments from the Indiana citizens.
IDEM uploaded its 2026 Integrated Report, including the finalized 2026 303(d) List of Impaired Waters to U.S. EPA’s Assessment and Total Maximum Daily Load Tracking and Implementation System (ATTAINS) online database on April 1, 2026.
IDEM’s 2026 Integrated Water Monitoring and Assessment Report Submittal, Including the 2026 303(d) List of Impaired Waters
- Indiana's 2026 Integrated Water Monitoring and Assessment Report to the U.S. EPA [PDF]
- Appendix A: Metadata and Definitions [PDF]
- Appendix B: Status of Category 4 Waters [PDF]
- Appendix C: IDEM’s Priority Ranking and 2026-2028 Schedule for Total Maximum Daily Load Development [PDF]
- Appendix D: IDEM’s 2026 Consolidated Assessment and Listing Methodology [PDF]
- Appendix E: IDEM’s Notice of Comment Period for the 2026 Draft 303(d) List [PDF]
- Appendix F: IDEM’s Responses to Comments on the Indiana Draft 2026 303(d) List of Impaired Waterbodies and Consolidated Assessment and Listing Methodology (CALM) [PDF]
- Appendix G: Trend and Trophic Status of Indiana’s Lakes
- Appendix H: Listing Tables Including Indiana’s Finalized 2026 303(d) List of Impaired Waters (Category 5) [XLS]
- Appendix I: Indiana’s 2026 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.