A fast and automated hydrologic calibration tool for SWAT

Abstract

<jats:title>Abstract</jats:title><jats:p>In order to apply hydrological models in the water resources investigation successfully, careful calibration and uncertainty analysis are required. Although many automatic calibration methods were developed, the time consumed for running the hydrologic model is still a problem for hydrologic modelers. To reduce the computational complexity and increase performance of the calibration procedure, a software package (Fast Automated Calibration Tool, FACT) that works on Soil and Water Assessment Tool (SWAT) was developed. Sequential Uncertainty Fitting Algorithm (SUFI‐2) was chosen to build the software package on, because SUFI‐2 combines optimization with uncertainty analysis and can handle a large number of parameters. SUFI‐2 implemented in SWAT‐CUP (a software program that was developed for SWAT) is very useful in an interactive manner, however; it has some drawbacks which are the time consumed, user interaction requirement and update problems of SWAT model files. In this study, the calibration procedure was implemented in a MATLAB script, which completes the full calibration in one single run. The developed tool was applied on Sarısu‐Eylikler Basin SWAT model that had <jats:italic>r</jats:italic><jats:sup>2</jats:sup> = 0.41, NSE = 0.11 between 1992 and 2010 without calibration. When the model was calibrated using SUFI‐2 in SWAT‐CUP, the model was improved to <jats:italic>r</jats:italic><jats:sup>2</jats:sup> = 0.57, NSE = 0.44, <jats:italic>P</jats:italic>‐factor = 0.69 and <jats:italic>R</jats:italic>‐factor = 1.00 at the end of 42 iterations using 100 simulation counts in each iteration. However; when the developed calibration tool was applied with 250 simulation counts without any user interaction for each iteration, the model was improved to <jats:italic>r</jats:italic><jats:sup>2</jats:sup> = 0.59, NSE = 0.57, <jats:italic>P</jats:italic>‐factor = 0.72, and <jats:italic>R</jats:italic>‐factor = 1.32 at the end of three iterations. Thus, the developed calibration procedure took a shorter time (unlike SUFI2 in SWAT‐CUP, FACT takes several hours) compared to SWAT‐CUP with minimum user involvement.</jats:p>