TR-494 Bacterial Source Tracking to Support Adaptive Management of the Arroyo Colorado Watershed Protection Plan: Final Report

Authors: A. Berthold, J. A. Benavides, E. Casarez, G. Di Giovanni, J. Archuleta-Truesdale

The Arroyo Colorado River, located in the Lower Rio Grande Valley of Texas, is a major tributary to the Lower Laguna Madre. Currently, it is impaired for a variety of pollutants, bacteria being one of those. Watershed planning efforts are ongoing and in order to identify what the primary causes and sources of bacteria are, watershed managers developed a monitoring strategy to conduct bacterial source tracking. Through this project, the Texas A&M AgriLife, Institute of Renewable Natural Resources visited with local agency personnel and decided that birds and wildlife were the key sources of interest. As a result, 254 fecal samples were collected from 27 known sources. Samples were shipped to the University of Texas School of Public Health – El Paso, isolated, and archived (409 isolates). Additionally, the University of Texas, Rio Grande Valley collected monthly water samples for one year at 10 different sites. Periodically samples were unable to be collected due to dangerous conditions but 113 samples were collected. Collected samples were taken to the Brownsville Public Utilities Board Analytical Laboratory for enumeration of E. coli and Enterococcus. Samples were also processed and shipped to University of Texas School of Public Health – El Paso for source tracking analysis. Results of source tracking indicated that 52% of the bacteria resulted from non-avian wildlife, 16% from avian wildlife, 10% from cattle, 9% from human, 10% unidentified, and 1% from pets, avian livestock, and other non-avian livestock. Results of this analysis will be used to guide the development of the Arroyo Colorado Watershed Protection Plan.