The Matagorda Bay watershed is located along the Texas Gulf Coast in the upper portion of the coastal bend region. This area is sometimes referred to as the golden crescent and consists of all or part of Calhoun, Colorado, DeWitt, Fayette, Gonzales, Jackson, Lavaca, Matagorda, Victoria and Wharton counties. The watershed is largely rural with grassland, cropland and forests dominating the landscape. The Matagorda Bay system consists of nine named bays: Carancahua, Chocolate, Espiritu Santo, Keller, Lavaca, Matagorda, San Antonio, Tres Palacios and Turtle. This bay system and the water bodies feeding it support a diverse and rich ecosystem that sustain a robust commercial fishery, abundant wildlife and more than 300 species of birds. The cities of Port Lavaca and Palacios are national leaders in shrimp and blue crab processing, respectively. Tourism is a major economic driver, as are the aluminum, chemical and petroleum processing industries.
Three river basins comprise the Matagorda Bay watershed: the Colorado-Lavaca, the Lavaca and the Lavaca-Guadalupe and are labeled as Basins 15, 16 and 17 respectively by the state. Within these basins, major water bodies include Tres Palacios Creek, the Lavaca and Navidad rivers and Lake Texana. A number of smaller water bodies also exist in the area and contribute stream flow into the bay system.
In Basin 15, the Tres Palacios Creek Tidal (Segment 1501) begins 1 kilometer upstream of the confluence of Wilson Creek in Matagorda County and flows approximately 9 miles into Tres Palacios Bay. Tres Palacios Creek Above Tidal (Segment 1502) extends from the confluence of Wilson Creek in Matagorda County up to the upstream portion of the creek in Wharton County. At its mouth, the Tres Palacios Creek drains an area of approximately 956 square miles in Calhoun, Jackson, Matagorda and Wharton counties. The impaired segment and its watershed drain approximately 258 square miles. Of this area, 61% is in Matagorda County and 39% is in Wharton County.
In Basin 16, the Lavaca River is the primary water conveyance to the coast. The river rises in Gonzales County and flows in a southerly direction into and through Lavaca and Jackson counties before flowing into Lavaca Bay. Water body segments in the basin include the Tidal portion of the Lavaca River, which extends from Lavaca Bay up to the river’s confluence with the Navidad River in Jackson County. The Lavaca River Above Tidal (Segment 1602_02) begins at the confluence of Campbell Branch and ends approximately 44 miles later, at the confluence with Beard Branch in Lavaca County while Segment 1602_03 begins at the confluence of Beard Branch and ends approximately 23 miles later, just south of Edna in Jackson County. At its mouth, the Lavaca River drains an area of approximately 2,316 square miles in Calhoun, Colorado, DeWitt, Fayette, Gonzales, Jackson, Lavaca, Victoria and Wharton counties. The watershed of both impaired segments drains approximately 829 miles in DeWitt (16% of the watershed), Fayette (0.2%), Gonzales (1%), Jackson (11%), Lavaca (71%), and Victoria (0.4%) counties. The basin also contains other water bodies that are not impaired due to elevated bacteria levels. These include the Navidad River, Lake Texana, East Mustang Creek, West Mustang Creek, Sandy Creek and Dry Creek.
Within Basin 17, Arenosa Creek (Segment 2453C) is the other impaired water body in the Matagorda Bay watershed and begins at J-2 Ranch Road and ends at the confluence of Garcitas Creek in Victoria County and is approximately 33 miles in length. At its mouth, Arenosa Creek drains approximately 1,045 square miles in Calhoun, DeWitt, Jackson, Lavaca and Victoria counties. The impaired segment and its watershed drain approximately 161 square miles in DeWitt (0.1% of the watershed), Jackson (45%), Lavaca (3%), and Victoria (52%) counties.
The 2012 Texas Water Quality Inventory and 303(d) List published by the Texas Commission on Environmental Quality (TCEQ) provides the following segment and AU descriptions for the impaired water bodies:
- Segment 1501 (AU 1501_01) (Tres Palacios Creek Tidal) - From the confluence with Tres Palacios Bay in Matagorda County to a point 1.0 km (0.6 miles) upstream of the confluence of Wilson creek in Matagorda County
- Segment 1602 (AU 1602_02 and 03) (Lavaca River Above Tidal) – From a point 8.6 km (5.3 miles) downstream of US 59 in Jackson County to a point 5.5 km (3.4 miles) upstream of SH 95 in Lavaca County
- Segment 2453C (AU 2453C_01) (Arenosa Creek) – From Garcitas Creek confluence upstream to J-2 Ranch Road