SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Sensitivity of calibrated parameters and water resource estimates on different objective functions and optimization algorithms 
Authors:Kouchi, D.H., K. Esmaili, A. Faridhosseini, S.H. Sanaeinejad, D. Khalili and K.C. Abbaspour 
Article ID:384 
URL (non-DOI journals): 
Broad Application Category:hydrologic only 
Primary Application Category:calibration, sensitivity, and/or uncertainty analysis 
Secondary Application Category:hydrologic assessment 
Watershed Description:13,000 km^2 Salman Farsi Dam drainage area and 51,000 km^2 Karkheh River, located respectively in southwest and northwest Iran. 
Calibration Summary: 
Validation Summary: 
General Comments: 
Abstract:The successful application of hydrological models relies on careful calibration and uncertainty analysis. However, there are many different calibration/uncertainty analysis algorithms, and each could be run with different objective functions. In this paper, we highlight the fact that each combination of optimization algorithm-objective functions may lead to a different set of optimum parameters, while having the same performance; this makes the interpretation of dominant hydrological processes in a watershed highly uncertain. We used three different optimization algorithms (SUFI-2, GLUE, and PSO), and eight different objective functions (R2, bR2, NSE, MNS, RSR, SSQR, KGE, and PBIAS) in a SWAT model to calibrate the monthly discharges in two watersheds in Iran. The results show that all three algorithms, using the same objective function, produced acceptable calibration results; however, with significantly different parameter ranges. Similarly, an algorithm using different objective functions also produced acceptable calibration results, but with different parameter ranges. The different calibrated parameter ranges consequently resulted in significantly different water resource estimates. Hence, the parameters and the outputs that they produce in a calibrated model are “conditioned” on the choices of the optimization algorithm and objective function. This adds another level of non-negligible uncertainty to watershed models, calling for more attention and investigation in this area. 
Keywords:calibration; uncertainty analysis; conditional parameters; SUFI-2; GLUE; PSO