Halls Bayou Tidal and Willow Bayou Watersheds
Photo Courtesy of the
Houston-Galveston Area Council
Counties: Brazoria, Galveston
Parameter: Bacteria
Basins: Bays and Estuaries, San Jacinto-Brazos Coastal
Segments: 2432B, 2432C
Assessment Units (AUs): 2432B_01, 2432C_01
On this page:
- Background and Goal
- Watershed Description
- Get Involved
- Approved I-Plan
- Adopted TMDLs
- Reports
- Contact Us
Background and Goal
High concentrations of fecal bacteria have been identified in Halls Bayou since 2012, and in Willow Bayou since 2014. Fecal bacteria are found in both human and animal waste. The presence of these bacteria may indicate a health risk to people who swim or wade in the bayou—activities referred to as “contact recreation” in the Texas Surface Water Quality Standards.
The goal of this project is to improve water quality in order to protect recreational uses. Toward that goal, TCEQ and stakeholders have developed total maximum daily loads (TMDLs) for bacteria in the bayous. Stakeholders have developed a regional Implementation Plan (I-Plan) to reduce bacteria in the Halls Bayou Tidal and Willow Bayou watershed, the Chocolate Bayou watershed, and the Mustang, Persimmon and New Bayou watersheds, which collectively form the larger Chocolate Bay watershed.
Watershed Description
Halls Bayou Tidal (Segment 2432C, AU 2432C_01) is a tributary of Chocolate Bay (Segment 2432), an embayment of West Galveston Bay. A tidal stream, Halls Bayou is 19.6 miles long and begins approximately six miles south-east of Alvin in Brazoria, with intermittent headwaters. The segment flows southeast past Halls Bayou Camp, briefly enters Galveston County, and then runs parallel to the Galveston County line into Halls Lake, through the Narrows, and into Chocolate Bay.
Willow Bayou (Segment 2432B) is a major freshwater tributary to Halls Bayou. The intermittent headwaters for Willow Bayou arise three miles southwest of Hitchcock in western Galveston County. The stream flows southwest to its mouth on Halls Bayou at the Brazoria County line.
In the upper reaches of the project area, topography ranges from flat coastal plain to rolling terrain, transitioning to flat terrain with shallow depressions in the lower reaches. Halls Bayou and its tributaries are typically sluggish due to the gentle sloping relief found on the coastal plain. Riparian vegetation is still common along portions of the bayou.
The TMDL watershed is primarily coastal tall grass prairies and marsh wetlands, with forested riparian areas consisting of water-tolerant hardwoods and conifers. This habitat supports a diverse population of both freshwater and saltwater fish. With extensive beds of seagrass, particularly wild celery, the bayous provide habitat for numerous waterfowl in the winter.
Land use in the area is primarily agricultural. Residential areas are concentrated primarily to the northeastern portion of the watershed in Galveston County, although a small area of the northern portion of the watershed in Brazoria County is also residential. There are no major cities or towns located in the watershed.
The Gulf Coast Water Authority maintains pump stations on Chocolate, Mustang, and Halls Bayous to supply up to 400,000 acre-feet of water per year for industrial, irrigation, and municipal purposes.
Get Involved
Staff from the Houston–Galveston Area Council (H-GAC) have been working with communities, interest groups, and local organizations to distribute information about this project and involve stakeholders in watershed improvement activities. All public meetings about this project are open to anyone interested. Watch for meeting announcements here. See meeting records in the "Get Involved" section of the H-GAC's webpage San Jacinto-Brazos Coastal Basin Bacteria Reduction Project .
Approved I-Plan
Community stakeholders worked together to create the Chocolate Bay I-Plan. The Commission approved the stakeholders' plan on August 12, 2026.
Adopted TMDLs
The Commission adopted these TMDLs on July 23, 2025. EPA approved them on Oct. 14, 2025, at which point they became an update to the state’s Water Quality Management Plan.
- Two TMDLs for Indicator Bacteria in the Halls Bayou Tidal and Willow Bayou Watersheds
- Response to Public Comment
- Response to EPA Comment
Reports
H-GAC staff completed a technical report that compiled and analyzed all available bacteria data and considered sources of the bacteria and their relative contributions.
- Technical Support Document, January 2025
Contact Us
Please email tmdl@tceq.texas.gov and mention the Halls Bayou and Willow Bayou bacteria project in the subject line. Or call us at 512-239-6682.
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