Assessing the impacts of grazing management practices on watershed hydrology and water quality
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Grazing management practices affect watershed hydrology and water quality by altering vegetation cover, soil properties and manure production. The objective of this study was to assess the impacts of alternate grazing management practices including light continuous (LC), heavy continuous (HC) and multi-paddock (MP) grazing, and no grazing (EX; exclosure) on watershed hydrology and water quality of a rangeland-dominated (71% rangeland) Clear Creek Watershed (CCW) in north central Texas using the Soil and Water Assessment Tool (SWAT). The SWAT model was calibrated and validated using the measured streamtlow and sediment concentration data at the watershed outlet over a 34-year (1980-2013) and 16-year (1994-2009) period, respectively. Results indicated that shining grazing management in the watershed from the baseline HC grazing to the improved MP grazing decreased surface runoff by about 47%, increased infiltration by 29%, and decreased streamflow by 27%. However, there were no significant differences in vapotranspiration (ET) among the grazing scenarios. Sediment load decreased from 90.1x1o3 to 54.4x1o3 ton (39.6%) under the MP grazing when compared to the baseline HC scenario. Improvements to grazing management have also resulted in a gradual reduction in high (0-10% exceedance interval) streamflows (and sediment loads), and thereby reduced the chances of flooding. Overall, the MP grazing practice was found to be the best grazing management practice in terms of water conservation, vegetation regrowth, water quality improvement and minimization of flood risk.
