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Watershed Protection Plan in Rural Texas Watersheds Using Spatial Tools

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  21st Century Watershed Technology: Improving Water Quality and Environment Conference Proceedings, 21-24 February 2010, Universidad EARTH, Costa Rica  701P0210cd.(doi:10.13031/2013.29428)
Authors:   Kyna E McKee, R Karthikeyan, Patricia K Smith
Keywords:   Keywords GIS, modeling, watershed, bacterial contamination, E coli

The Spatially Explicit Load Enrichment Calculation Tool (SELECT) and Load Duration Curves (LDCs) were both used to develop a watershed protection plan a rural watershed in Texas, Buck Creek, that is impaired due to E. coli bacteria. Watershed protection plans are difficult to implement in rural watersheds because hydrologic flow and water quality data are often sparse and not equally distributed across the watershed. SELECT is an automated Geographical Information System (GIS) tool that can assess pathogen loads in watersheds using spatial factors such as land use, population density, and soil type. LDCs were used to determine the Total Maximum Daily Loads (TMDLs) under different hydrologic flow conditions. The U.S Geological Survey (USGS) program LOAD ESTimator (LOADEST) was used to estimate the E. coli loads in each stream at each monitoring location in relation to flow rate. The LOADEST loads were then compared with the TMDLs and observed loads to calculate percent reduction for each flow condition. SELECT was used to identify the non-point sources most likely contributing to E. coli contamination. The watershed protection plan was developed by combining the use of SELECT and LDCs for the watershed. The results show that the historic data collected for the Buck Creek Watershed shows a percent load reduction of 44 percent is needed to lower the bacterial contamination to regulatory standards. The LDC that includes historic data collected between 1997 and 2009 only has a percent load reduction needed for high flow conditions. The SELECT results indicated the potential bacteria contributors as cattle and feral hogs.

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