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Atascosa River: Evaluating the Aquatic Life and Recreational Uses

A completed assessment project to evaluate concentrations of dissolved oxygen and bacteria in the Atascosa River in South Central Texas

photo of kicknet sampling in the Atascosa River
Atascosa River

Counties: Atascosa, Bexar, Frio, Karnes, Live Oak, McMullen, Medina, Wilson
Parameters: Bacteria and Dissolved Oxygen
Basin: Nueces River
Segment: 2107

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Project Description

In the Atascosa River in south central Texas, water quality testing found elevated levels of bacteria and low concentrations of dissolved oxygen. The TCEQ worked with the Nueces River AuthorityExit the TCEQ and other stakeholders to develop a plan to address these conditions.

High concentrations of bacteria may indicate a health risk to people who swim or wade in the rivers—activities referred as “contact recreation” in the state’s Standards for surface water quality. Dissolved oxygen is essential for the survival of aquatic life, and so is used to indicate whether conditions support the “aquatic life use” in the Standards.

In 2009, proposed revisions to the state’s recreational use standard prompted the TCEQ to re-evaluate development of a TMDL, which had been underway since fall 2004. The agency decided to evaluate the aquatic life and contact recreation uses at the same time to gain a fuller understanding of the biological and flow conditions for the entire stream.

Using protocols developed by the TCEQ’s Water Quality Standards Group, the TMDL Team managed a study to support both an aquatic life use attainability analysis (ALUAA) and a recreational use attainability analysis (RUAA) on the entire length of the Atascosa River. UAAs are comprehensive examinations of the physical, chemical, and biological factors that determine whether a particular use is attainable in a specific area of a water body.

The recommendations of the Standards Group for the contact recreation uses based on the RUAA have not yet been released, though a report is available (see link under "Reports"). Based on the ALUAA, the Atascosa River was divided into three segments: one unclassified segment (intermittent flow with pools) and two classified segments. The Standards Group recommended a high aquatic life use for the Lower Atascosa River (Segment 2107) and an intermediate aquatic life use for the Upper Atascosa River (new Segment 2118). These recommendations related to the aquatic life use were submitted to the EPA in 2014. EPA has not approved or disapproved the recommendations. Contact the TCEQ to inquire about the status of these analyses.

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Public Participation

The TCEQ informed stakeholders about this project at public meetings and in print and electronic media. Meetings about the project were open to all.


The TCEQ Standards Team will use these reports to analyze use attainability and decide whether to recommend revisions to the standards.

ALUAA Report for the Atascosa River

RUAA report for the Atascosa River

Final reports from the 2004 assessment to determine the extent and severity of impairments to the recreational and aquatic life uses of the river are provided below.

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For More Information

Please e-mail us at and mention the Atascosa River project in the subject line. E-mail the TCEQ to inquire about the status of the UAAs. Or call us at 512-239-6682.

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communities working together taking care of our rivers, lakes, and bays