Abstract: To optimize the energy management of base station (BS) and enhance the interaction between BS and the grid is an effective way to reduce the operational costs of 5G BS and improve grid flexibility. However, the existing studies on "BS-grid" interactions mostly concern telecommunication demands and ignore the constraints of the grid. Moreover, with the introduction of water-cooling and its waste heat utilization, the energy management problem of 5G BS has evolved into a water-energy management problem involving the interactions among BS, power and water distribution networks, and heat consumers. Therefore, in the context of the large-scale 5G application and integrated energy systems, this paper presents the coordinated scheduling of water-cooled 5G BS and regional integrated electricity-water system (IEWS). Considering the sleep mode switching, waste heat utilization and "water/energy prosumer" characteristics of BS, the water-energy nexus and the water/energy demand responses are modeled, and the coordination mechanism between BS and regional IEWS is further proposed with its three-stage scheduling method. The effectiveness of the proposed method and its benefits in reducing the operational costs of IEWS and 5G BS as well as promoting wind and photovoltaic power accommodation are verified by two case studies.