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Surface water quality

The Texas Commission on Environmental Quality, known as the TCEQ, regularly monitors the condition of the state's surface waters and assesses the status of water quality every two years. This assessment is submitted to the Environmental Protection Agency (EPA) and is published on the TCEQ Web site as the Texas Water Quality Inventory and 303(d) List.

The requirements for the Inventory and List are codified in the federal Clean Water Act, Sections 305(b) and 303(d), Title 30 of the Texas Administrative Code and in rules and guidance established by the TCEQ.

Since 2002, the 303(d) list and the 305(b) report have been published as one document with two major parts: The Inventory, which is the status of all water in the state, and the 303(d) List, which identifies waters that do not meet one or more standards of use.

Water Quality Standards

Water quality standards are a combination of designated use and the criteria necessary to attain and maintain that use. The uses prescribe the purposes for which the water should be fit—such as recreation, support of aquatic life or drinking water supply. The criteria define the instream conditions necessary to support those uses.

Criteria can either be numeric, such as a limit on the amount of a pollutant, or narrative, such as a prohibition on a certain condition in the water.

When permitted dischargers are using inadequate levels of treatment to maintain the water quality, then water quality standards are the basis for the control of pollutants. These standards can be site specific or applied generally and any one water body might have several designated uses. These standards also define an antidegredation policy that protects existing uses.

Classifications

To better manage all the waters in the state of Texas, the major rivers, lakes and estuaries have been assigned tracking numbers called classified segments. The classified segments are given numbers that correspond to the major river basin that they are located in. For example, Brazos River (one of the state's longest rivers), is divided into 57 separate segments and designated as Basin 12. The segments are given 4 digit numbers, with the first two digits representing the basin, so Lake Mexia would be 1210 since it is in the Brazos River Basin.

Since there are so many bodies of water in the state, not all are classified in the standards. For example, some of the tributaries that flow into a river may not be classified but may need to be looked at. This tributary would be assigned a tracking number and letter to correspond with the watershed it resides in for management purposes, such as 1210A or 1210B. This would be known as an unclassified segment.

In the assessment, both classified and unclassified segments are known as water bodies.

Major River Basins of Texas

Categories of Use and Attainment

The inventory assigns each of the water bodies to one of five categories to provide information to the public, EPA and internal agency programs about water quality status and about management activities. The higher the category number, the higher the level of effort is required to manage the water quality.

Water bodies that are in category 5 constitute the 303(d) List and require action by the state to restore water quality. Category 1 waters are meeting all their uses, and simply require routine monitoring and preventive action.

The combination of the water use with the pollutant or condition of concern is called an impairment. For example, the concentration of dissolved oxygen is one of the criteria used to determine the support of aquatic life. If dissolved oxygen levels are low, one impairment would exist for the water body.

Since a water body has several uses, it may fall into different categories for different uses. In that case, the overall category for the water body is the one with the highest category number.

Total Maximum Daily Load

According to the EPA, a TMDL or total maximum daily load is a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the pollutants source. A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The calculation must include a margin of safety to ensure that the water body can be used for purposes the state has designated. The calculation must also account for seasonal variation in water quality.

Waters in a Category 5a must develop a TMDL and a plan to implement it. For the State of Texas, the number of impairments addressed by TMDL projects has increased from 63 in 2000 to 190 in 2003. There may be several TMDLs for one body of water. A TMDL must also allocate this load to the various sources of pollution in the watershed. The state must then develop an implementation plan to achieve loading allocations as defined by the TMDL. TMDLs are subject to EPA approval; implementation plans are not.

The TCEQ must undertake new projects to restore the water quality with each new assessment, while continuing to implement plans for waters listed in previous years. For most listing years, around half of the water bodies have been subsequently removed from the list as a result of TMDLs, further analysis and monitoring, or changes in assessment methods. TMDLs have been completed or are in progress for about 25 to 35 percent of the impairments, depending on the listing year, in Texas. The remaining water bodies are addressed either from the analysis of the standards or targeted monitoring to document the degree and extent of the impairment.

Surface water FAQs

How is water quality monitored?

The Texas Commission on Environmental Quality (TCEQ) regularly monitors the condition of the state's surface waters and assesses the status of water quality every two years. This assessment is submitted to the EPA and is published on the TCEQ Web site as the Texas Water Quality Inventory and 303(d) List.

What is a TMDL?

According to the EPA, a TMDL or total maximum daily load is a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the pollutants source. A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources.

Am I in a TMDL?

To determine if you are in a TMDL, identify the watershed that you are located in. Next, check the current 303(d) list to determine if your watershed is named and to identify the associated water quality parameter.

Do I contribute to the TMDL in my area?

In short, all activities, whether agricultural, industrial, municipal or recreational, contribute to the water quality in your watershed. Depending on the constituent of concern, some activities may be more significant contributors than others.

How does a TMDL designation get removed?

A plan for management of the TMDL in your watershed must be developed and effectively implemented in order to remove your watershed from the 303(d) list of impaired water bodies.

Publications

The Watershed Management Approach
Russell A. Persyn, Molly Griffin, Amy T. Williams and Clint Wolfe

Links

CSREES Southern Region Water Quality Program

Texas Commission on Environmental Quality

US Environmental Protection Agency