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Mid Cibolo Creek: A Project for Dissolved Oxygen

An completed project to assess and improve dissolved oxygen concentrations in Mid Cibolo Creek in South Central Texas
photo of Mid Cibolo Creek
Mid Cibolo Creek

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Counties: Comal, Guadalupe, Bexar
Parameters: Dissolved oxygen
Basin: San Antonio River
Segment: 1913

Background and Goals

In Mid Cibolo Creek in south central Texas, water quality testing found low concentrations of dissolved oxygen. The program’s South Central Texas Streams project verified that the impairment was severe enough to warrant development of a TMDL for the creek.

Oxygen, which dissolves in water, is essential for the survival of aquatic life. While the amount of dissolved oxygen in water fluctuates naturally, various human activities can cause unusually or chronically low levels of dissolved oxygen, which may harm fish and other aquatic organisms.

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Public Participation

Project staff informed the public about this project through public meetings, which were open to everyone.

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Project Status

After completion of the draft TMDL, the TCEQ determined that since a single regulated discharger was believed to be the primary source of the impairment, it was not necessary to complete and submit a TMDL to the EPA.

The TCEQ expects that upgrades completed to the discharging facility in 2007 will ameliorate the low dissolved oxygen conditions in the creek. The state will continue to monitor the stream to ensure that the facility upgrades are sufficient to restore conditions that support a healthy aquatic community.

Subsequently, in 2008, the dissolved oxygen impairment in Mid Cibolo Creek was removed from the state’s 303(d) list and reclassified in the state’s Water Quality Inventory and List. The dissolved oxygen impairment is assigned to Category 4b, which is the classification for water bodies in which a standard is not met, but for which a TMDL is not required because other control requirements are reasonably expected to result in the attainment of the standards.

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Project Documents

Final reports from the assessment to determine the extent and severity of the impairment in the stream. (PDF.)

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For More Information

For additional information regarding this project, please e-mail us at, and mention the Mid Cibolo Creek TMDL in the subject line. Or call us at 512-239-6682. 

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