The Medina River below Diversion Lake and Medio Creek have been considered impaired due to elevated E. coli concentrations that routinely exceed state water quality standards since 2010 and 2018 respectively.
These waterways are used for swimming, fishing, kayaking and more throughout the year, and water from Diversion Lake is used for irrigation within the watershed and as potable water for the San Antonio Water System (SAWS). The Medina River contains multiple sensitive recharge features and contributes significant volumes of recharge to the Edwards Aquifer. Increasing development pressure expanding outward from the San Antonio metropolitan area is adding further environmental stress to the system.
In 2021, the Texas Water Resources Institute (TWRI) worked with the Texas Commission on Environmental Quality (TCEQ) to create a data summary report of the Medina River Watershed below Diversion Lake. The report summarizes previous research in the watershed, analyzes historic water quality data, and identifies potential sources of pollution.
The project also included meetings with targeted stakeholders to discuss the next steps in the watershed and overall goals. The feedback from stakeholders during the data summary process indicated a preference for developing a Watershed Protection Plan (WPP).
TWRI and the San Antonio River Authority (SARA) are now partnered in the development of a WPP to address water quality trends and issues throughout the watershed. This plan will be stakeholder driven and pull from existing information found in the Medina River Holistic Watershed Master Plan and TWRI summary report.