Little Brazos River
Tributaries Bacteria Assessment
The central watershed of the Brazos River consists of one classified water body, the Brazos River above Navasota River (Segment 1242),
and a number of unclassified waterbodies on tributary systems. This segment extends from the Lake Brazos Dam in Waco 183 miles downstream to its confluence
with the Navasota River southeast of College Station and its watershed encompasses approximately 2,705 square miles. Land use in the watershed is generally
agricultural with two urban areas (Waco and Bryan/College Station) and a few large industrial facilities and quarries.
In 2002 a water quality data analysis determined that eight unclassified water bodies within the central watershed had bacteria concentrations
exceeding state water quality standards for contact recreation. As a result these waterbodies were placed on the Texas §303(d) List of Impaired Waters. Three additional
unclassified segments were added to the 2006 §303(d) List bringing the total number of water quality impairments (bacteria) on segment 1242 to eleven.
Five of the waterbodies impaired for bacteria are located within very close proximity of each other in Robertson County and share similar land use
and water quality characteristics. They are all tributaries to the Little Brazos River (Segment 1242E). The five waterbodies in this project’s study area are Campbells
Creek (Segment 1242I), Mud Creek (Segment 1242K), Pin Oak Creek (Segment 1242L), Spring Creek (Segment 1242M), and Walnut Creek (Segment 1242O). The study area encompasses
327 square miles, almost entirely within Robertson County. The land use in the area is primarily agricultural with several small communities.
The 2006 §303(d) List identifies all five segments in the study area as Category 5c, meaning that the waterbody does not meet applicable water quality
standards for one or more designated uses by one or more pollutants and that additional data and information will be collected before a TMDL is scheduled.
TCEQ and TSSWCB established a joint technical Task Force on Bacteria TMDLs in September 2006 charged with making recommendations on cost-effective and
time-efficient bacteria TMDL development methodologies. The Task Force recommended the use of a three-tier approach that is designed to be scientifically credible and accountable
to watershed stakeholders. The tiers move through increasingly aggressive levels of data collection and analysis in order to achieve stakeholder consensus on needed load reductions
and strategies to achieve those reductions. In June 2007 the TCEQ and TSSWCB adopted the principles and general process recommendations into an updated joint-agency TMDL guidance document.
In accordance with the Memorandum of Agreement Between the TCEQ and the TSSWCB Regarding TMDLs, Implementation Plans, and Watershed Protection Plans, the TSSWCB has
agreed to take the lead role in addressing the bacteria impairments for the five segments in the study area. Through this and associated projects, the TSSWCB and BRA will work with local
stakeholders to progress through the data collection and analysis components of the first two tiers of the Task Force recommended three-tier approach.
The objective of this project is to provide sufficient water quality data to characterize bacteria loadings across the various flow regimes at a number of locations
throughout the study area.