Abstract: The calculation of reservoir utilization and regulation is the core work of water resources demonstration, however, for water supply reservoirs without inflow runoff observation data, the calculation of inflow is the key step in the calculation of reservoir utilization and regulation. According to the actual situation of reservoirs in the area which lack of data, the inflow runoff was calculated based on the rainfall runoff coefficient method, and the runoff coefficient was reasonably determined by several methods such as hydrological analogy and water balance. According to the principle of reservoir dispatching, the balance of supply and demand of water resources was calculated in a ten-days basis according to the long series of time calendars. The results of regulation calculation under different water intake scales were obtained, the guarantee degree of water supply of different water intake scale and its influence on other water users such as irrigation and power generation were evaluated , so as to achieve the purpose of rational allocation and optimization of water resources.