Numerical flow analysis in turbomachinery is an indispensable tool for water turbines design. Following the design of axial runner, the energetic and cavitation characteristics can be predicted using the numerical method. In this paper it is described how the multiobjective genetic algorithm aids the human decision of the best design solution, based on objective functions obtained by numerical flow analysis. Theoretical and empirical knowledge of the design procedure enables to start the optimization procedure with good initial geometry. A very effective procedure for developing water turbines has been provided merging design procedure, numerical flow analysis and multiobjective genetic algorithm.