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An Auto-Calibration Tool for the Agricultural Policy Environmental eXtender (APEX) Model

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 57(4): 1087-1098. (doi: 10.13031/trans.57.10601) @2014
Authors:   Xiuying Wang, Haw Yen, Qingying Liu, Junguo Liu
Keywords:   APEX, Auto-calibration, Hydrology, Sediment.

Abstract. The Agricultural Policy Environmental eXtender (APEX) model has emerged as one of the key scientific tools applied worldwide for assessing a variety of water and environmental issues. The Fortran-coded model has also seen a rapid progression in user interface development for facilitating input management. However, an auto-calibration tool has not yet been developed for it. In this study, an open-source auto-calibration tool (APEX-CUTE) was developed using a dynamically dimensioned search algorithm with optimization options of aggregating different objective functions. The case study in the upper Bawanghe River watershed in Inner Mongolia, China, resulted in average percent errors within 20% and Nash-Sutcliffe efficiency (NSE) values from 0.47 to 0.72 for monthly and annual streamflow and sediment yields during the calibration period. The validation period had NSE values from 0.41 to 0.62 and average percent errors within 15%. APEX-CUTE is a computationally efficient and flexible tool for enhancing APEX calibration. Factors that may affect the model performance are discussed, and the forthcoming improvements to the APEX-CUTE are described.

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