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Water 2018, 10(7), 898;

Evaluating the Effects of Watershed Size on SWAT Calibration

Interstate Commission on the Potomac River Basin, Rockville, MD 20850, USA
National Soil Erosion Research Laboratory, USDA-Agricultural Research Service, West Lafayette, IN 47907, USA
Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA
Author to whom correspondence should be addressed.
Received: 31 May 2018 / Revised: 30 June 2018 / Accepted: 2 July 2018 / Published: 6 July 2018
(This article belongs to the Section Water Quality and Ecosystems)
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The Soil and Water Assessment Tool (SWAT) has been calibrated in many watersheds of various sizes and physiographic features. However, it is still unclear whether SWAT calibration parameters will produce satisfactory results if they are implemented in watersheds of different sizes. Evaluating the transferability of SWAT calibration parameters between watersheds of different sizes will provide insight into whether it is acceptable to calibrate SWAT in one watershed and apply the optimized parameters in different size watersheds by assuming both watersheds have similar physiographic properties. This study investigated the influence of watershed size on the SWAT model calibration parameters transferability between four watersheds (CCW = 680 km2, F34 = 183 km2, AXL = 42 km2, and ALG = 20 km2) located in Northeastern Indiana. The results show that calibrating SWAT at one size and applying the optimized parameters at different watershed sizes of similar physiographic features provided satisfactory simulation results. The size watershed at which SWAT was calibrated had little effect on streamflow predictions. Soluble nitrogen loss estimates were improved when calibration was performed at the larger CCW watershed while calibrating SWAT at the smaller AXL and ALG watersheds produced improved statistical indicator values (NSE, R2, and PBIAS) for soluble P and total P when applied to the larger CCW and F34 watersheds. View Full-Text
Keywords: nutrients; optimization; runoff; simulation; Soil and Water Assessment Tool (SWAT); SWAT-CUP; watershed management nutrients; optimization; runoff; simulation; Soil and Water Assessment Tool (SWAT); SWAT-CUP; watershed management

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Wallace, C.W.; Flanagan, D.C.; Engel, B.A. Evaluating the Effects of Watershed Size on SWAT Calibration. Water 2018, 10, 898.

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