Given the fact that hydropower energy is the third largest source of electricity generation and also the most important renewable energy producer in the world, the optimal use of the huge and expensive source of water is essential. In this study, water cycle metaheuristic algorithm was used for optimization of the hydropower operation of Jiroft reservoir located in Halilrood basin (south of Iran) for a period of 223 months (from October 2000 to April 2019). The decision variables in the hydropower energy optimization model of the reservoir are the optimal release values of the monthly hydropower output from the reservoirs. After verifying the reliability of the WCA algorithm using several standard benchmark functions, a model was developed for optimal hydropower operation of the Jiroft reservoir. Also, the results of the algorithm were compared with the results of known metaheuristic algorithms of the Harmony search Algorithm (HS) and Imperialist Competitive Algorithm (ICA). The WCA, ICA and HS algorithms were capable to generate energy 7203, 273.66, and 7115.78 MW during the statistical period, respectively. Also, the objective function value for WCA, ICA and HS algorithms, was obtained 4.78, 5.82, and 8.63, respectively. The results revealed that the MSA algorithm was the superior algorithm in optimal hydropower operation.