“…In the heuristic method, the objective function is expressed as a fitness function. The definition of the fitness function in the case of optimization of hydrological model parameters has been proposed by many previous researchers, including the minimization of root mean square error or RMSE (Hsu, 2015;Wang et al, 2012;Sulianto et al, 2018;Sulianto et al, 2020), minimization of sum square error (SSE) (Darikandeh et al, 2014;Paik et al, 2005), maximizing Nash-Sutcliffe model efficiency or NSE (Xuesong Zhang et al, 2008;Bao et al, 2010;Tolson and Shoemaker, 2007), minimization of mean square error or MSE (Ngoc et al, 2013), minimization of relative error or RE (Santos et al, 2011;Kuok et al, 2011)…”