Abstract: In order to effectively ensure the needs for water safety during the short-term optimal dispatch of cascaded reservoirs, a model for cascade reservoir operation is established. A regulatory water safety factor is embedded into the model to achieve the water safety objective. A Vague set is used for the water safety measurement in the development of the model, and the regulatory water safety factor is the regulatory water safety factor is introduced for calculating the discharge constraint of the cascaded reservoirs, which is considered as part of water safety requirements. With the obtained discharge constraint, the regulatory water safety factor can thus be embedded into the short-term optimal dispatch model for cascade reservoir operations. The regulatory factor in the model can be defined according to the water safety requirements, and the corresponding short-term optimal dispatch scheme can thus be determined accordingly. The model is applied to optimize the cascade reservoir operation in the middle reach of Jialing River, consisting of three multipurpose reservoirs for navigation and hydroelectric power production. Results show that the model is able to achieve the maximum benefit from the short-term optimal dispatch of cascaded reservoirs, while ensuring the needs for water safety. Embedding the regulatory water safety factor into the model not only improves the benefit from cascade reservoir operations, but also preserves the water safety requirements.