Simulating runoff from small grazed pasture watersheds located at North Appalachian Experimental Watershed in Ohio

Authors: GAUTAM, SAGAR - University Of Missouri; MBONIMPA, ERIC - Air Force Institute Of Technology, Afit; KUMAR, SANDEEP - South Dakota State University; BONTA, JAMES - Retired ARS Employee

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Runoff from grazing pasture lands can impact water quality in receiving streams if not well managed. Management consists of conservation practices to reduce runoff and pollutants transport. Simulation models have been effectively used to design and implement these conservation practices. The Agricultural Policy Environmental Extender (APEX), a process-based hydrologic model, was used in this study to simulate the management impacts on surface runoff from field data collected at three small grazed pasture watersheds located at the North Appalachian Experimental Watersheds near Coshocton, Ohio. After calibrating and validating the model runs using measured runoff data, the model was used to simulate the long=term impacts of different management scenarios on surface runoff. After validation, the APEX model was run for long-term scenarios (37 yr, 1975-2011) to analyze the impacts of soil properties and management on surface runoff. Results showed that the APEX model simulated surface runoff reasonably well during calibration. The model results indicated that keeping the watershed land use as a hay meadow instead of grazing significantly reduced cumulative runoff by 58-67%. Buffer strips of perennial grasses resulted in decreased simulated runoff. To simulate the impacts of soils on runoff, the surface (0-5 cm) soil properties of the toe position were applied to the entire grazed watershed, resulting in reduced (=5%) surface runoff. The simulation results demonstrate the benefits of hayed meadow over grazed pasture, and further predict decreased runoff due to soil-property changes and buffer strips.

Technical Abstract: Runoff from grazing pasture lands can impact water quality in receiving streams if not well managed. Management consists of conservation practices to reduce runoff and pollutants transport. Simulation models have been effectively used to design and implement these conservation practices. The Agricultural Policy Environmental Extender (APEX), a process-based hydrologic model, was used in this study to simulate the management impacts on surface runoff from three small grazed pasture watersheds located at the North Appalachian Experimental Watersheds near Coshocton, Ohio. Specific objectives of this study were to 1) calibrate the APEX model and test runoff predictions against measured runoff and 2) simulate the long-term impacts of different management scenarios on surface runoff. Results show that the APEX model simulated surface runoff reasonably well with the coefficient of determination (R2) and Nash-Sutcliffe efficiency values varying from0.49 to 0.72 and from 0.25 to 0.60 for calibration and validation, respectively. After validation, the APEX model was run for 37 yr (1975-2011) for long-term scenarios to analyze the impacts of soil properties and management on surface runoff. Data from this study indicated that keeping the watershed land use as a hay meadow instead of grazing significantly reduced cumulative runoff by 58-67%. Buffer strips of perennial grasses resulted in decreased simulated runoff. To simulate the impacts of soils on runoff, the surface (0-5 cm) soil properties of the toe position were applied to the entire grazed watershed. Subsequently, the change in soil properties resulted in reduction (=5%) in surface runoff. The simulation results from the present study demonstrate the benefits of hayed meadow over grazed pasture and further predict the decreased trend of runoff due to soil properties change and buffer strips.