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Carters Creek TMDL Data Project

The Texas Water Resources Institute conducted water quality monitoring and gathered information on sources of bacteria in Carters Creek to inform and refine strategies in the Carters Creek Total Maximum Daily Load Implementation Plan.


Carters Creek (Segment 1209C) and its tributaries are located in central Brazos County. The watershed drains about 57 square miles of land before it empties into Navasota River. A large portion of the watershed land use is urban, especially in the upper watershed where Carters Creek originates in Bryan, TX. Urbanization, specifically impervious cover (e.g., concrete, asphalt, roofs), can negatively impact water quality by reducing water infiltration into the soil and increasing the volume of stormwater runoff, and the pollutants it carries, being discharged to streams, rivers, and lakes.

Carters Creek has not meet all water quality standards because bacteria concentrations exceed the criteria used to evaluate attainment of the contact recreation use since 1999. These bacteria are naturally found in the intestines of humans, livestock, wildlife, and pets. Although they are not generally disease-causing, their presence in water indicate the potential presence of disease-causing microorganisms from fecal contamination. Therefore, higher levels of fecal bacteria in water mean a higher risk to humans of contracting diseases by ingesting contaminated water during swimming, wading, or kayaking—activities, called “contact recreation,” in the state’s standards for water quality.

TCEQ and partners developed a total maximum daily load (TMDL) for the Carters Creek watershed, which determines the amount of a pollutant a water body can receive and still meet water quality standards. In 2012, the TMDL stakeholder group developed a TMDL Implementation Plan for Carters Creek which identified a need for a more detailed understanding of the concentrations and sources of bacteria throughout the watershed.

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Project Description

Texas Water Resources Institute (TWRI) conducted additional water quality monitoring to determine the variability of fecal bacteria concentrations across time and location in the watershed. This information established a clear baseline of water quality data that could be used to track progress of best management practices in reducing nonpoint source pollution and improving water quality in the watershed.

TWRI also compiled information and locations of potential sources of pollution throughout the watershed, including wastewater and stormwater infrastructure. These data are stored in a Geographic Information System and can be used by watershed managers to track system failures or illicit discharges. The project was completed in February 2016. Project reports are available on the Carters Creek Watershed Water Quality website .

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For More Information

To find out more about the NPS Program, call 512-239-6682 or e-mail us at

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