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TMDLs and Their Implementation

What total maximum daily loads (TMDLs) are, how they are developed and implemented, and how the state evaluates the water quality of rivers, lakes, and estuaries.
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What the TMDL Program Does

The Total Maximum Daily Load (TMDL) Program works to improve water quality in rivers, lakes, and estuaries in Texas.

TMDLs are developed for surface waters that are quality-limited due to a pollutant or adverse condition. Based on the environmental target in the TMDL, the state develops an implementation plan to mitigate sources of pollution within the watershed and restore impaired uses. A TMDL is like a budget for pollution—determining the extent to which pollutant concentrations must be reduced to meet quality standards.

An implementation plan (IP) usually puts the TMDL into action by outlining the steps necessary to reduce pollutant loads through regulatory and voluntary activities. In some instances, TMDLs are implemented through watershed protection plans (WPPs).

The TMDL program is authorized by and created to fulfill the requirements of Section 303(d) of the federal Clean Water Act and its implementing regulations.

For an overview of the TCEQ's approach to managing the quality of surface waters in Texas, see Preserving and Improving Water Quality.

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How TMDLs and Implementation Plans Are Developed

TMDLs are developed by TCEQ personnel, by cooperating state agencies, or by independent contractors at the direction of the TCEQ. Occasionally, organizations develop TMDLs independently of the TCEQ; these are referred to as “third-party” TMDLs. Ultimately, the TCEQ is responsible for the adoption of all TMDLs in Texas and their subsequent approval by the U.S. Environmental Protection Agency.

Both a TMDL and its implementation plan, or I-Plan, are needed when a river, lake, or bay is water quality-limited due to a pollutant or adverse condition. The TCEQ asks people who live in the watershed—the stakeholders—to assist in development of both products. Often, work starts on the I-Plan and the TMDL at roughly the same time, since it can take a while to discuss all the options and for all the parties to agree.

TMDL Development

The development of TMDLs is a scientifically rigorous process of data collection and analysis. The TCEQ asks people who live and work in the watershed—the stakeholders—to share their knowledge about local conditions and help make decisions such as the best locations for collecting water samples. The TCEQ engages other public or private organizations as needed to help with specific technical issues. And the TCEQ shares the status of TMDL development with stakeholders at key decision points in the process.

I-Plan Development

We all have to work together to develop an implementation plan. Local residents have the best understanding of local conditions, their goals, and how to get there. They work on how to share the load of reducing pollution, identify financial and technical resources available to them, and ways to get resources they need.

The final I-Plan outlines:

  • What to do over the next one to five years
  • Who will do it
  • When it will be done
  • How we will gauge improvement

For example:

  • Wastewater treatment facilities may commit to reducing the amount of pollution in their discharges.
  • Cities might work to control runoff from their streets through management of stormwater.
  • Farmers and ranchers might decide to use new or improved practices that make runoff water cleaner.
  • Government agencies or educational institutions might help by providing educational and promotional materials.

Stakeholders meet periodically to measure their progress based on their plan, and to determine whether the plan needs to be revised. Success depends on everyone doing their part.

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How Are TMDLs Funded?

The Texas Legislature appropriates funds to the TCEQ and the Texas State Soil and Water Conservation Board to support the development and implementation of TMDLs. Both agencies also use federal money to support the program. Funding for implementation is frequently from local governments or privately-owned facilities that discharge wastewater.

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Surface Water Quality: How It Is Measured

For an overview of the TCEQ's approach to defining and managing the quality of surface waters in Texas, see Preserving and Improving Water Quality.

Standards Define Water Quality

To measure water quality, we must first define it. The Texas Surface Water Quality Standards are rules designed to:

  • designate the uses, or purposes, for which a water body should be suitable;
  • establish numerical and narrative goals for water quality throughout the state; and
  • provide a basis on which TCEQ regulatory programs can establish reasonable methods to implement and attain the state’s goals for water quality.

All standards are protective; that is, they signal a possibility that water quality may be inadequate to attain its designated uses.

The Texas Integrated Report of Surface Water Quality

The Texas Integrated Report of Surface Water Quality is an overview of the status of surface waters of the state, including concerns for public health, fitness for aquatic species and other wildlife, and specific pollutants and their possible sources. The 303(d) List, a subset of the report, identifies waters that do not attain one or more standards for their use. Water bodies identified in Category 5a of the 303(d) List are those impaired waters for which the state plans to develop total maximum daily loads (TMDLs). All impaired waters include those Category 4 in addition to Category 5. Category 4 includes impaired waters for which TMDLs have already been adopted, or for which other management strategies are underway to improve water quality.

Read Texas Surface Water Quality: What Is It, and How Is It Measured? (PDF) for a brief overview of water quality standards and the means by which surface water quality is evaluated.

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Preserving and Improving Water Quality: Programs of the TCEQ

The publication Preserving and Improving Water Quality provides an overview of the way the TCEQ evaluates the quality of surface waters in Texas, and the programs and practices the TCEQ employs to protect and restore surface water quality. Order printed copies from our Publications section.

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For More Information

For more information about the TMDL Program, contact Louanne Jones at 512/239-2310, or send us an e-mail at

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