In this paper, a new method of water pumping scheduling in a water distribution system with providing balancing reserves to power systems is proposed. This method enables to obtain a daily schedule of pumping water and balancing reserves, which is based on prices of electric energy and balancing reserves, hourly water demand profile, and properties between water flow quantity and consumption electricity of water pumps. The proposed method consists of an optimization model which is formulated by Mixed Integer Linear Programming (MILP). The constraints about the fluctuation of the volume of water in a reservoir, which is occurred by providing the balancing reserves, is added into the proposed model. Adding these constraints, stable water distribution is enabled even when the balancing reserves are activated. To verify the validity of the proposed method, simulations of water pumping scheduling in some cases were done. As a result, net operational cost was decreased when water pumps provided the balancing reserves. Moreover, the operational feasibility of providing the balancing reserve from water pumps is clarified.