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Total Maximum Daily Load Program: Communities Working Together to Improve Water Quality

A program that brings communities together to take care of Texas by improving the quality of their streams, lakes, and bays through development of total maximum daily loads (TMDLs) and their implementation plans (I-Plans).

A TMDL is a scientifically-derived target that tells us the greatest amount of a particular substance that we can add to a waterway and still keep it healthy. These substances are not necessarily harmful in and of themselves. For example, phosphorus is an essential nutrient, but too much phosphorus can lead to an overgrowth of algae, which in turn can make the water taste bad and reduce the amount of oxygen available to fish and other creatures that live in the water.

Another example is bacteria, which occur naturally in both human and animal waste. But too much bacteria can make it more hazardous to swim or wade in a creek, lake, or bay—activities called “contact recreation” in the state’s standards for water quality.

The TMDL gives us a measurable way to target our efforts to protect and improve the quality of our streams, lakes, and bays.

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Projects of the TMDL Program

Protecting people and aquatic species by reducing pollution in impaired or threatened waterways.

TMDLs and Their Implementation

What TMDLs are and how TCEQ and stakeholders make a difference in the quality of our waterways.

Developing TMDL Projects

Guidelines for organizations that develop or implement TMDLs for Texas waterways.

Get Involved

About TMDLs, I-Plans, and water quality.


Stakeholder Meetings.

Participate in TMDL Projects

How to get involved in your watershed.

Join the TMDL News E-mail List

Sign up to receive news by e-mail from the Total Maximum Daily Load Program.

Impaired Waters and TMDLs
All Impaired Waters, 2020 Adobe Acrobat PDF Document

Categories 4 and 5 of the most recent EPA-approved Texas Integrated Report of Surface Water Quality.

Segments with TMDLs

The TCEQ must consider TMDLs in permits it issues under the Texas Pollutant Discharge Elimination System (TPDES). Permits identify the classified segment to which wastewater is discharged.

Summary of Completed TMDLs and Implementation Plans

TMDL is complete; I-Plan development or approval may be incomplete. Includes dates of adoption or approval by the commission and EPA.

Preserving and Improving Water Quality 

An overview of how the TCEQ defines, measures, evaluates, and manages the quality of surface waters in Texas.

Watershed Action Planning

Strategies and plans for protecting and improving the quality of the state's streams, lakes, and estuaries.

Hydrography Data and Map-Based Data Viewers

GIS-based data viewers and GIS data for classified segments and other surface water information.

For More Information

Call 512-239-6682, or send us an e-mail at