Lower Leon Creek: A Project to Assess Bacteria and Dissolved Oxygen
County: Bexar, Medina
Parameter: Bacteria and Dissolved Oxygen
River Basin: San Antonio
Segment: 1906
Background and Goals
In Lower Leon Creek, low dissolved oxygen concentrations indicate that conditions are not optimal for aquatic life. In addition, concentrations of bacteria have been measured at levels that might pose a health risk for swimmers.
Oxygen gas, 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 dissolved oxygen levels, which may harm fish and other aquatic organisms.
Bacteria from human and animal waste can indicate the presence of disease-causing microorganisms. People who swim or wade in the creek might be at risk. The state’s standards use the term contact recreation to refer to swimming or other recreational activities during which it is likely a person may ingest natural waters.
Learn more about water quality standards and management by reading the TCEQ’s publication Preserving and Improving Water Quality.
Status
- A two-year intensive effort to collect additional data about dissolved oxygen and indicator bacteria was completed in 2010.
- Review and analysis of the new data showed the creek is supporting its contact recreation use.
- The TCEQ and the San Antonio River Authority will continue to monitor Leon Creek under the TCEQ’s Surface Water Quality Monitoring and Clean Rivers programs.
Public Participation
Public participation is an important component of the Lower Leon Creek TMDL project. The TCEQ coordinates local involvement through the San Antonio River Authority 
with the help of the Bexar Regional Watershed Management Water Quality Focus Group , a public participation forum.
For More Information
Please e-mail us at tmdl@tceq.texas.gov, and reference the Lower Leon Creek bacteria project in the subject line. Or call us at 512/239-6682.
