Simulation And Prediction Of Salinity And Temperature In Qingcaosha Reservoir By Using Delft3D

Qingcaosha Reservoir is located in the lower reaches of the Yangtze River estuary.It is the largest estuary river reservoir in China.It is an important source of water in Shanghai.Water quality of Qingcaosha Reservoir is directly related to the water supply security in Shanghai.Qingcaosha Reservoir is located at special geographical position,which leads to the risk of saltwater intrusion in the winter dry season.In order to deal with this problem,the special operation condition management was adopted to make it have the particularity of storing water and avoiding salt.On the other hand,in recent years,due to the continuous increase in the Yangtze River water nitrogen and phosphorus nutrients with the water flow into the reservoir,the water slowed down and temperature rose.The reservoir has the risk of cyanobacteria.In order to study the impact of reservoir management measures on the overall water quality of the reservoir,it is necessary to grasp the hydrodynamic conditions and the changing regularity of Qingcaosha Reservoir.Therefore,this study used Delft3 D software to establish the three-dimensional hydrodynamic model of Qingcaosha Reservoir,simulated and predicted the changes of salinity and temperature of reservoir.It can be used to explore the potential problems of water quality and provide scientific science for the management and operation of Qingcaosha Reservoir.The main results of this paper are as follows:1.Based on the collected hydrological survey data and related meteorological data,the three-dimensional flow field model of Qingcaosha reservoir was established by Delft3D-Flow module.By comparing with the measured data,the flow field model of the grasses was determined and validated.The fitting effect is reasonable,which indicates that the model can be used as the basis of long-term hydrodynamic model.The simulation results shows that the flow velocity in the reservoir area is always changed and the flow velocity of the upstream simulation point is affected by the diversion.The flow velocity stratification at surface layer and bottom layer is not obvious,and the flow field is mainly affected by the wind speed.2.Based on the proven flow field model,the three-dimensional hydrodynamic model of long-term grass sand was established by using the measured temperature and salinity as the boundary condition for nearly one year.According to the specific temperature and salinity measured in the library,the temporal and spatial changes of reservoir temperature and salinity were analyzed.It is concluded that the change of salinity and temperature in the upper reaches of the reservoir is influenced by the diversion of the reservoir,and the influence of the wind speed on the drainage process of the reservoir is also important.In the long-term operation of the reservoir,with the upstream reservoir water quality changes,changes in salinity and temperature occur first in the reservoir reclamation area on the south side,then in the north also changes,the change trend of lower salinity and temperature is relatively slow.There is no obvious stratification of salinity in the reservoir,but the surface temperature in the lower reaches and the bottom layer are obviously different during the summer.3.Based on the assumption of future warming and sea level rise under authoritative research reports,this paper analyzes the possible change of water quality in Qingcaosha Reservoir in the future.According to these problems,the model operation condition is set up,and the corresponding simulation analysis is carried out to provide the scientific basis for the reservoir operation and management in future.The concrete simulation is mainly embodied in two aspects:a.The diversion was assumed in the saltwater tide.In the condition of salinity's diversion,it explored Qingcaosha Reservoir's limit in water diversion period in future.b.The Ocean model was assumed by varying degrees of temperature change in the future to explore the influence of different long-term temperature changes on reservoir water temperature.The influence of the change of water temperature in the reservoir on algae and the corresponding measures for operation and management were analyzed.