Lower San Antonio River Watershed - Instream Flows Study - Biological Collection Summary Report

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San Antonio River Authority

Because of greater demands for fresh water by growing communities like San Antonio, the Texas Legislature has directed Texas Parks and Wildlife Department (TPWD), Texas Commission on Environmental Quality (TCEQ), and Texas Water Development Board (TWDB), in cooperation with other appropriate governmental agencies such as the San Antonio River Authority (SARA), to conduct an instream flow data collection effort. This instream flow collection effort will help determine appropriate flow and habitat conditions necessary to support a sound ecological environment for resident fish species and will help to gain a better understanding of the fish assemblage dynamics within the Lower San Antonio River (SAR) watershed. The Lower SAR watershed was selected as a priority study reach based on the potential for significant reuse of water and the uncertainty of future water development strategies. Methodologies for determining appropriate flow conditions necessary to support a sound ecological environment will also be studied.

SARA field personnel have assisted the State of Texas Agency Staff with reconnaissance, sample site selection, biological and habitat sampling as well as data collection efforts throughout the Lower SAR and Lower Cibolo Creek watersheds. Evaluation of the fish community, flow measurements and habitat assessments were conducted at five sites on the Lower SAR (Loop 1604 in Bexar County, Floresville City Park in Wilson County, Conquista Crossing in Karnes County, SH 72 in Karnes County, and Riverdale Rd. in Goliad County) and three sites on the Lower Cibolo Creek (FM 539 in Wilson County, FM 537 in Wilson County and FM 389 in Karnes County). Data collected from these sampling efforts will provide much needed habitat and baseline data of the fish community composition within the lower SAR watershed. Collection methods included boat and backpack electrofishing as well as seining efforts in as many habitat types as possible. Individual biological collection efforts were segregated by habitat types from which the samples were collected. Photographs and global positioning system coordinates were recorded from the mid-point of each habitat type. Measurements were made of the average habitat depth, dominant substrate, and current velocity within each habitat type.

Data collected from this effort will help to characterize current instream flow conditions within the Lower SAR watershed and will help to make future flow management recommendations needed to sustain the resident biological community and ensure an adequate water supply for the future needs of all communities within the Lower SAR watershed. The instream flow methodologies that result from this effort will influence the approach that SARA will undertake in the future concerning water related endeavors.

San Antonio, instream flow