Watershed Evaluation and Total Maximum Daily Loads (TMDL) Section

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What is a TMDL? 

A TMDL is a scientific determination of the maximum amount of a given pollutant that a surface water can absorb and still meet the water quality standards that protect human health and aquatic life. Waterbodies that do not meet water quality standards are identified as "impaired" for the particular pollutants of concern - nutrients, bacteria, mercury, etc. - and TMDLs must be developed, adopted and implemented to reduce those pollutants and clean up the waterbody.

The threshold limits on pollutants in surface waters - Florida's surface water quality standards on which TMDLs are based - are set forth in Chapter 62-302 and Chapter 62-303, Florida Administrative Code (F.A.C.).

TMDL development is a part of the department's Integrated Water Resource Monitoring Network (IWRMN) fulfilling the "Tier III" monitoring efforts that are designed for regulatory purposes to address site-specific questions. These efforts are designed to ensure that Section 106(e)(1) of the Clean Water Act is met which defines the prerequisites for monitoring the state's aquatic resources. Please see the department's IWRMN Monitoring Strategy for Fiscal Years 2025 - 2029 that provides additional information explaining the components of the monitoring and assessment programs.

What are the basic steps in the TMDL program? How does it work?

1. Assess the quality of surface waters-are they meeting water quality standards? (Surface Water Quality Standards - Chapter 62-302).
2. Determine which waters are impaired-that is, which ones are not meeting water quality standards for a particular pollutant or pollutants. (Impaired Waters Rule (IWR) - Chapter 62-303).
3. Establish and adopt, by rule, a TMDL for each impaired water for the pollutants of concern-the ones causing the water quality problems. (TMDLs - Chapter 62-304).
4. Develop, with extensive local stakeholder input, Basin Management Action Plans (BMAPs) that:

• Implement the strategies and actions in the BMAP.
• Measure the effectiveness of the BMAP, both continuously at the local level and through a formal re-evaluation every five years.
• Adapt-change the plan and change the actions if things aren't working.
• Reassess the quality of surface waters continuously.

We are working on a more comprehensive approach to protecting Florida water quality involving basin-wide assessments and the application of a full range of regulatory and non-regulatory strategies to reduce pollution. The Total Maximum Daily Load is the heart of this comprehensive approach.

Locations of the DEP's Adopted TMDLs

• For locations of TMDLs in Florida, view our interactive TMDL map and Chapter 62-304, F.A.C.
• Please help us improve our service by providing feedback on the status and development of TMDLs in Florida and how could we improve our communication and waterbodies targeted for TMDL development. To provide feedback please contact Kevin O'Donnell, 850-245-8469.