Study on designed flows of water function reaches based on distributed hydrological model

Based on a distributed hydrological model and its effective simulation of river flow in dry season, this paper proposed a convenient and efficient method to compute the designed flows of water function reaches. Applying the method into Songhua River Basin, the paper calculated the designed flows of 300 water function reaches in the basin, simulated and analyzed their variations in the scenarios of 2020 and 2030 year, which took into consideration the growing water use, the changing landuse and the construction of large water diversion projects. The results show that there is an overall downtrend of the designed flows in the future scenario. Attach importance to the notably declined designed flows of Fuyu and Haerbin station, the paper proposed an optimal resolution by setting a lowest discharge of upstream Fengman Reservoir in the value of 230m3/s.