TR-527 Mission and Aransas TMDL Effectiveness Monitoring

Authors: Ed Rhodes, Allen Berthold

Historical water quality monitoring data for the Mission and Aransas rivers, located on the Texas Gulf coast, had shown that the water bodies did not meet water quality standards for recreation due to elevated levels of Enterococci. The tidal segments of the Mission and Aransas rivers were classified as impaired beginning with the 2004 Texas Water Quality Inventory and 303(d) List. This subsequently led to the development of a Total Maximum Daily Load (TMDL) and Implementation Plan to address pollutants in these waterbodies. Under the current project, water quality monitoring was conducted from November 2018 to June 2020, occurring twice per quarter, to supplement the ongoing quarterly Clean Rivers Program monitoring. Supplemental monitoring shows a marked decline in Enterococci levels over the duration of the project, suggesting that water quality in the watersheds may be improving.