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Evaluation of Different Objective Functions Used in the SUFI-2 Calibration Process of SWAT-CUP on Water Balance Analysis: A Case Study of the Pursat River Basin, Cambodia

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Department of Agricultural and Environmental Engineering, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-8-5 Saiwai-cho, Fuchu-shi, Tokyo 183-8538, Japan
2
Institute of Agriculture, Tokyo University of Agriculture and Technology, 3-8-5 Saiwai-cho, Fuchu-shi, Tokyo 183-8538, Japan
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Research Center for Climate Change, Nong Lam University, HoChiMinh 700000, Vietnam
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Department of International Environmental and Agricultural Science, Tokyo University of Agriculture and Technology, 3-8-5 Saiwai-cho, Fuchu-shi, Tokyo 183-8538, Japan
5
Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-8-5 Saiwai-cho, Fuchu-shi, Tokyo 183-8538, Japan
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Institute of Technology of Cambodia, Faculty of Hydrology and Water Resources Engineering, PO Box 86, Russian Confederation Boulevard, Phnom Penh 12156, Cambodia
*
Author to whom correspondence should be addressed.
Water 2020, 12(10), 2901; https://doi.org/10.3390/w12102901
Received: 8 September 2020 / Revised: 14 October 2020 / Accepted: 15 October 2020 / Published: 17 October 2020
(This article belongs to the Section Hydrology and Hydrogeology)
Many calibration techniques have been developed for the Soil and Water Assessment Tool (SWAT). Among them, the SWAT calibration and uncertainty program (SWAT-CUP) with sequential uncertainty fitting 2 (SUFI-2) algorithm is widely used and several objective functions have been implemented in its calibration process. In this study, eight different objective functions were used in a calibration of stream flow of the Pursat River Basin of Cambodia, a tropical monsoon and forested watershed, to examine their influences on the calibration results, parameter optimizations, and water resources estimations. As results, many objective functions performed better than satisfactory in calibrating the SWAT model. However, different objective functions defined different fitted values and sensitivity rank of the calibrated parameters, except Nash–Sutcliffe efficiency (NSE) and ratio of standard deviation of observations to root mean square error (RSR) which are equivalent and produced quite identical simulation results including parameter sensitivity and fitted parameter values, leading to the same water balance components and water yields estimations. As they generated reasonable fitted parameter values, either NSE or RSR gave better estimation results of annual average water yield and other water balance components such as annual average evapotranspiration, groundwater flow, surface runoff, and lateral flow according to the characteristics of the river basin and the results and data of previous studies. Moreover, either of them was also better in calibrating base flow, falling limb, and overall the entire flow phases of the hydrograph in this area. View Full-Text
Keywords: SWAT model; SUFI-2; objective functions; calibration; water balance components SWAT model; SUFI-2; objective functions; calibration; water balance components
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MDPI and ACS Style

Sao, D.; Kato, T.; Tu, L.H.; Thouk, P.; Fitriyah, A.; Oeurng, C. Evaluation of Different Objective Functions Used in the SUFI-2 Calibration Process of SWAT-CUP on Water Balance Analysis: A Case Study of the Pursat River Basin, Cambodia. Water 2020, 12, 2901.

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