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Bacterial Source Tracking to Support Adaptive Management of the Arroyo Colorado Watershed Protection Plan

Project Description: The Arroyo Colorado currently has low dissolved oxygen levels within the tidal segment, not meeting the aquatic life use designated by the State of Texas and described in the Water Quality Standards. This has been the case for every 303(d) list prepared by the state since 1996. In addition, bacteria has always been a parameter of concern and as of 2006, the Arroyo became impaired due to high bacteria levels. There are many challenges associated with restoring water quality in the Arroyo Colorado Watershed. The watershed is one of the most productive agricultural areas in the State; however, it also has one of the fastest growing populations of any region in the state as well, which increases the threat for bacterial impairments. Surface water irrigation on consumptive crops is widely used. This bacteria impairment not only poses a human health threat through contact recreation, but also potentially through consuming food that is grown with this water. In order to address the bacteria impairment, projects such as this one are being implemented in the watershed.

Through this project, a water quality monitoring regime will be employed that will help decision makers make appropriate recommendations for addressing the bacteria impairment in the revision of the Arroyo Colorado WPP. Monthly sampling will be conducted at 10 sampling sites as identified in the WPP. UTB will conduct water sampling, measure field parameters (pH, temperature, conductivity, and dissolved oxygen), and deliver samples to the NELAP-accredited Brownsville Public Utilities Board Analytical Laboratory for enumeration of E. coli and Enterococcus. Data will be stored in a database maintained by UTB containing field and lab analysis data.

TWRI will conduct a source survey to identify possible sources of bacteria in the watershed. Based on this assessment, TWRI, in consultation with UTSPH, will collect 200 known source fecal samples and ship them to UTSPH according to established protocols for processing and inclusion in the Texas E. coli BST Library. Further, Brownsville PUB Analytical Laboratory will prepare water samples for transport to UTSPH for BST analysis. To assess and identify different sources contributing to bacterial loadings, UTSPH will conduct library-dependent BST and analyze E. coli isolates using the ERIC-PCR and RiboPrinting combination method. Results of the source survey, assessment of bacterial levels at each site, and BST results will be presented to the Arroyo Colorado Watershed Partnership (ACWP) for incorporation into the WPP.

Project Location: Arroyo Colorado watershed in Hidalgo, Cameron and Willacy Counties

Project Costs: Federal ($465,555); Non-Federal ($167,343); Total ($632,898)

Project Participant(s): TSSWCB, Texas Water Resources Institute, University of Texas at Brownsville and Texas Southmost College- Department of Chemistry and Environmental Sciences, University of Texas- Houston School of Public Health, El Paso Regional Campus

Project Workplan: 12-10

Project Quality Assurance Project Plan(s): Monitoring- 12-10 

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