Extending Field-Scale Information to the Watershed Scale Using the Apex and SWAT Models.

Field scale management system impacts surface runoff at the field outlet and these small scale management systems may affect the stream flow. This study was conducted to evaluate the impacts of small scale management change on stream flow. The Agricultural Policy Environmental eXtender (APEX) and Soil Water Assessment Tool (SWAT) models were used for this study. The APEX, a field scale and SWAT, a watershed scale hydrologic models are capable of simulating the management impacts on stream flow. The specific objectives of the study were to: (i) calibrate the model using modern calibration approach, and (ii) simulate the impacts of field scale management change on stream flow. The study was conducted on Little Mill Creek watershed, located in Coshocton and Holmes counties of Ohio. This watershed encompasses a small portion of the North Appalachian Experimental Watershed (NAEW) at Coshocton, Ohio. The small watershed scale information used for scaling is taken from the model built for (grazed pasture and no-till) watersheds located at NAEW. The results demonstrate the benefits of integrating the field scale model (APEX) with watershed scale model (SWAT) model. The integrated model indicated that the small scale management change scenario imported for APEX to SWAT impacted the stream flow.