Evaluating the SWAT model to predict streamflow, nitrate loadings and crop yields in a small agricultural catchment

摘要

Abstract. This study aimed to evaluate the applicability of the Soil and WaterAssessment Tool (SWAT) to predict streamflow, nitrate loadings and cropyields for a small agricultural catchment in northeastern Germany. To thisend, a 167ha catchment was delineated consisting of 10?hydrologicalresponse units. Daily data for streamflow and nitrate loadings from 2004 to2015 were used to calibrate and validate the model, while annual values forcrop yields (winter wheat, winter barley, rapeseed, maize silage) wereavailable. In addition, the detailed field maps provided by the local farmerwere used to implement exact crop rotations and nitrogen fertilization intothe model. Nash-Sutcliffe-Efficiencies for streamflow were 0.54 during thecalibration and 0.57 for the validation period. The modeling performance fornitrate loadings were lower with 0.31 for the calibration and 0.42 for thevalidation period. The average crop yields were reproduced well, while SWATfailed to reproduce the inter-annual crop yield variations. A scenarioanalysis revealed that a slight decrease of nitrogen fertilization leads tosignificant reductions in nitrate loadings, while crop yields remained on ahigh level. The outcome of the study may help practitioners to operateaccording to an economic and environmental optimal N management.Nevertheless, experimental studies with varying fertilization intensities atcatchment scale are needed to underpin the modeling results.