The impacts of climate change on the runoff volume of Melen and Munzur Rivers in Turkey based on calibration of WASMOD model with multiobjective genetic algorithm

The investigation of the impacts of climate change on the total runoff volume in two different watersheds named Melen and Munzur in Turkey is the main purpose of this study. The dynamically downscaled outputs of GFDL-ESM2M, HadGEM2-ES, and MPI-ESM-MR general circulation models (GCMs) under RCP4.5 and RCP8.5 scenarios were used as climatic forces to drive a hydrological model called WASMOD-D. The parameters of WASMOD-D model were optimized by using the multi-objective genetic algorithm (GA). In order to wane the influences of uncertainties which are rooted in GCMs, in addition to using various models, the biases in climatic parameters (precipitation and temperature) were corrected using the quantile-mapping method, with respect to the observed data during the reference period (1971–2000). Future projections were developed by taking two 30-years periods into the account: (1) mid-period (2041–2070) and (2) late future (2071–2100). The results of this study show that the total water volume will decrease in accord with precipitation diminution and temperature increase during the mid-time and late future in both watersheds. The percentage of the decline in runoff volume by the end of the 21st century were found as 15.42 and 26.65 on average for Melen and Munzur rivers, respectively. However, the monthly distribution of the runoff was found to be not changed during the current century.