Spatially explicit load enrichment calculation tool and cluster analysis for identification of E. coli sources in Plum Creek Watershed, Texas



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According to the 2004 303(d) List, 192 segments are impaired by bacteria in the State of Texas. Impairment of streams due to bacteria is of major concern in several urban watersheds in Texas. In order to assess, monitor and manage water quality, it is necessary to characterize the sources of pathogens within the watershed. The objective of this study was to develop a spatially explicit method that allocates E.coli loads in the Plum Creek watershed in East Central Texas. A section of Plum Creek is classified as impaired due to bacteria. The watershed contains primarily agricultural activity and is in the midst of an urban housing boom. Based on a stakeholder input, possible sources E. coli were first identified in the different regions of the watershed. Locations of contributing non-point and point sources in the watershed were defined using Geographic Information Systems (GIS). By distributing livestock, wildlife, wastewater treatment plants, septic systems, and pet sources, the bacterial load in the watershed was spatially characterized. Contributions from each source were then quantified by applying source specific bacterial production rates. The rank of each contributing source was then assessed for the entire watershed. Cluster and discriminant analysis was then used to identify similar regions within the watershed for assistance in selection of appropriate best management practices. The results of the cluster analysis and the spatially explicit method were compared to identify regions that require further refinement of the SELECT method and data inputs.