Author(s): Zhaowei Liu; Yongcan Chen; Zhongshun Li; Dejun Zhu
Keywords: Middle Route Project for South-to-North water transfer; Miyun Reservoir; Deeply-submerged inflow; Temperature distribution; EFDC
Abstract: The water from Mudanjiang River will be pumped into Miyun Reservoir in a deeply submerged way when the Middle Route Project (MRP) for South-to-North water transfer is finished in 2015. The temperature distribution in Miyun Reservoir will be modified due to the temperature difference between the submerged inflow and the bottom of the reservoir. In the present paper, the effect of deeply-submerged inflow on the temperature distribution in Miyun Reservoir is studies with the code of EFDC. With a large volume of water body and relative small inflows and outflows, Miyun Reservoir is regarded to be stratified during spring and summer and wind is the main driving force of the flow. To model the turbulent kinetic energy induced by wind stress correctly, wave-turbulence process, in both wave breaking and non-breaking ways, is included in the Mellor-Yamada turbulence model used in EFDC. As a result, the vertical mixing coefficient is calculated more accurately and the epilimnion is predicted more reasonable. The improved model is validated by the measured data in 2010 with a good agreement. The spatial and temporal changes of the temperature in Miyun Reservoir are predicted from 2015 to 2019, using the improved model. The results show, with the deeply-submerged inflow, the water stage rises more quickly. The temperature distributions are similar from one year to another and the thicknesses of epilimnion keep nearly constant on the same day of different years, but the thickness of hypolimnion increases with the leveling up of water stage. However, a mixing zone is found nearby the entrance due to the temperature difference between the submerged inflow and the bottom of the reservoir. The size of mixing zone varies from day to day but the maximum size is limited in the scope of 800m in diameter. With the simulations we reached the conclusion that the effect of the deeply-submerged inflow from MRP on the temperature distribution in Miyun Reservoir is limited in a small area nearby the inflow.