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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Plant Science

First Advisor

Sandeep Kumar


Long-term hydrologic data are required to quantify the impacts of management and climate change on runoff at the field scale where management practices are applied. This study was conducted to evaluate the impacts of long-term management and climate change on runoff from a small watershed managed with no-till (NT) and grazed pasture systems. Further, study was conducted to evaluate the performance of the two widely used hydrologic models; Agricultural Policy Environmental eXtender (APEX) and Soil and Water Assessment Tool (SWAT) for their ability to simulate stream flow. In this study, two different calibration approaches, the parameter estimation (PEST) and sequential uncertainty domain parameter fitting (SUFI-2) method were employed for model evaluation and calibration of APEX and SWAT models, respectively. The specific objectives of the study were to: i) to calibrate the APEX model using an inverse modeling approach (PEST-APEX) (ii) simulate the impacts of cropping management, grazing management, climate change, and tillage system on runoff, and (iii) compare simulation results generated by two widely used hydrologic models, APEX and SWAT. The study was conducted using four small watersheds (one no-till and three grazed pasture watersheds) located in the North Appalachian Experimental Watersheds (NAEW) near Coshocton, Ohio and one larger watershed; Millcreek watershed located in Coshocton and Holmes counties of Ohio. Data show that the use of PEST-APEX and SUFI-2 resulted in efficient calibration of the models compare to trial and error methods.The results also indicate that the corn-soybean-rye rotation under no-till system is significantly beneficial for controlling runoff compared to continuous corn. The climate change scenarios indicate that runoff from the no-till watershed is the most sensitive to the precipitation, and interactions of precipitation, temperature, and carbon dioxide concentrations. Results from grazed pasture watershed study demonstrate the benefits of hayed meadow over grazed pasture and conclude that surface runoff is affected by soil properties, and can be reduced by using buffer strips of perennial grasses at the downslope of the watershed. Further, the results from the Millcreek watershed study indicate that the SWAT can simulate the stream flow reasonably well compared to the APEX due to better ground water parameterization and finer subdivision of the watershed.

Library of Congress Subject Headings

Runoff -- Simulation methods
Agricultural pollution


Includes bibliographical references (pages 125-127).



Number of Pages



South Dakota State University


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