Numerical Simulation Of Oxythermal Distribution In Miyun Reservoir And The Impact Of The South-to-North Water Diversion Project

Miyun Reservoir is the only surface water resource in Beijing,the water level decreased significantly during recent years.The Middle Routine Project(MRP)for the South-to-North Water Diversion Project was constructed to meet the water demand in Beijing and Miyun Reserovir will serve to store excessive water temporarily in the first5 years.The water from MRP will change the oxythermal regimes in Miyun Reservoir.In this paper,a one dimensional vertical water quality model was established to simulate the vertical distribution of water temperature and dissolved oxygen in Miyun Reservoir.The model includes hydrodynamic process,water temperature process and dissolved oxygen(DO)process.The model was calibrated and validated using field data of water temperature and DO in Miyun Reservoir and then used to simulate the vertical distributions of water temperature and DO in Miyun Reservoir.The model was then used to analysis the impact of the change of water level and incoming flows on oxythermal regimes in Miyun Reservoir.As the water level declined,the water temperature in the surface depth did not change,while the annual mean value of water temperature increased in the bottom depth.The DO concentration in the surface depth remained unchanged,while the annual mean value of DO concentration in bottom depth significantly increased.The increase of inflows had no significant impact on temperature in the surface depth,while the temperature in the middle and bottom depth increased in winter.Three scenarios were developed and used to predict the oxythermal regimes of Miyun Reservoir with the entrance of water from MRP.The rise of water level and the increase of incoming flows had different impact on the oxythermal regimes in Miyun Reservoir.The rise of water level had greater impact on the vertical distribution of water temperature,while the vertical distribution of DO was decided by the increase of inflows.