Ambient Microbial Testing in the San Antonio River Watershed, a Three-Pronged Approach

Oral Presentation

Prepared by S. Donovan
San Antonio River Authority, 600 E. Euclid Ave, San Antonio, Texas, 78212, United States


Contact Information: sdonovan@sara-tx.org; 210-302-3258


ABSTRACT

The San Antonio River (SAR) watershed is comprised of 13 classified stream segments with the headwaters located just north of downtown San Antonio. The San Antonio River Authority (SARA) is the primary agency tasked with water quality monitoring in the SAR basin. Water quality research began at SARA in the 1960’s and has progressed to include extensive ambient and storm water quality sampling. In recent years, SARA has developed a three pronged approach to ambient bacterial testing: (1) quantify E. coli levels through routine monitoring, (2) attempt to identify bacterial hotspots with intensive sampling and (3) identify sources of pollution to inform load reduction efforts using bacterial source tracking (BST). Routine sampling stations and frequencies are evaluated and appropriately modified based on data collected and collaborative discussions with the Texas Commission on Environmental Quality (TCEQ), the water quality regulatory agency in Texas. If a sampling station is observed to have E. coli levels inconsistent with other stations in the same waterbody SARA will conduct intensive sampling in an effort to identify the stretch of increased loading. Intensive sampling is typically conducted every stream mile in the waterbody of concern; in addition, samples are collected from all atypical inputs observed by field staff (e.g. pipes and seeps). The source identification step is achieved using library-dependent and –independent BST methods. Library-dependent analysis, which results in three-way and seven-way splits, provides exceptional resolution but is cost-prohibitive when compared to the library-independent alternative. Library-independent analysis is conducted by analyzing genetic markers from a single source organism (e.g. human, horse, feral hog) to determine presence/absence in a given water sample.The San Antonio River (SAR) watershed is comprised of 13 classified stream segments with the headwaters located just north of downtown San Antonio. The San Antonio River Authority (SARA) is the primary agency tasked with water quality monitoring in the SAR basin. Water quality research began at SARA in the 1960’s and has progressed to include extensive ambient and storm water quality sampling. In recent years, SARA has developed a three pronged approach to ambient bacterial testing: (1) quantify E. coli levels through routine monitoring, (2) attempt to identify bacterial hotspots with intensive sampling and (3) identify sources of pollution to inform load reduction efforts using bacterial source tracking (BST). Routine sampling stations and frequencies are evaluated and appropriately modified based on data collected and collaborative discussions with the Texas Commission on Environmental Quality (TCEQ), the water quality regulatory agency in Texas. If a sampling station is observed to have E. coli levels inconsistent with other stations in the same waterbody SARA will conduct intensive sampling in an effort to identify the stretch of increased loading. Intensive sampling is typically conducted every stream mile in the waterbody of concern; in addition, samples are collected from all atypical inputs observed by field staff (e.g. pipes and seeps). The source identification step is achieved using library-dependent and –independent BST methods. Library-dependent analysis, which results in three-way and seven-way splits, provides exceptional resolution but is cost-prohibitive when compared to the library-independent alternative. Library-independent analysis is conducted by analyzing genetic markers from a single source organism (e.g. human, horse, feral hog) to determine presence/absence in a given water sample.