The OPTIGES module solves the problem of monthly water assignment in a river basin to the different demands and storage reservoirs. To do this it solves an optimization problem for a period of one or more years. In this way, it calculates the optimal assignment of water for each period needing very few data, almost only the physical description of the basin (links, reservoirs and demands). This is a great advantage for its use in systems where little information is available or when we want to obtain general yearly conclusions. On the contrary, the monthly simulated management is not directly comparable to reality because in real systems it is impossible to know beforehand what will be the available water resources. Because of this, it requires from the user an additional effort on results interpretation to translate them to useful conclusions for management. An efficient way to validate this interpretation is to use it and improve it with the use of the SIMGES module.