Lake Trasimeno is a closed lake in Central Italy and in historically its water level has been affected by wide fluctuations mostly depending on the climate. The lake has suffered many water crises due to water scarcity and in recent decades, droughts have also severely affected the economic and environmental situation. The aim of this study was to analyze the possibility of limiting these severe level fluctuations by evaluating of feasible water resource management policies that could also reduce the environmental stress of this area. Therefore, a specific decision support system (DSS) has been developed in order to simulate different scenarios for the entire water system of the Trasimeno area. In particular, the hydrological model implemented in the DSS allowed for the simulation and validation of different management policy hypotheses for the water resource in order to mitigate environmental and water crises for the Lake Trasimeno. Results indicated that it is possible to transfer a certain amount of water from nearby reservoirs without affecting the availability of the resource for specific users. In this way, Lake Trasimeno can benefit both from an increase in water levels in the lake, so a possible better situation in quantitatively and qualitatively.