| As the most important lake in Jiangxi Province,as well as the biggest lake in the middle and lower reaches of the Yangtze River,the excellent water environment of Poyang Lake plays a vital role in maintaining the ecological security of the Poyang Lake and the entire Yangtze River Basin.In recent years,with the rapid social and economic development of the basin,the demand for water resources is increasing day by day,which result to decreasing water area as well as aggravated and long-lasting dry season.In order to change this situation,Jiangxi province put the construction of the water hydraulic project of Poyang Lake on the agenda once again.Therefore,the in-depth study to the water environment of Poyang Lake and the new water hydraulic project have important theoretical and practical significance on the water environment,especially on the continuity assessment of Poyang Lake and the Yangtze River.Among which water temperature distribution and water age variation are two important aspects.Based on the previous research,EFDC is adopted in this paper to establish the Poyang Lake model on simulating the water temperature distribution of the Poyang Lake area and the influence of the water hydraulic project on the lake water age.The main findings are:(1)The water temperature of Poyang Lake is low in the west yet high in the east during spring and winter and low in the east while high in the west during summer.There is a stratification in the vertical direction,which becomes obvious along the north to the south,from the west to the east.It mainly exists in the central lake area and northeast lake in summer and autumn with high temperature and high water level.The vertical distribution of Poyang Lake is the mixed type on the whole due to its limited time and range.Its stratification is related to temperature,water level,lake current,topography,the interaction of rivers and lakes and solar radiation.(2)Lack of hydrodynamic drive,the northeast Lake Bay of Poyang Lake and the southern lake beach bears poorer lake water exchange and older water age compared with the whole lake.While with the Yangtze River under the top of the recharge,the water can get a better exchange in a short term which leads to the younger water age.In general,the Poyang Lake hydraulic Project will not change the process of hydrodynamic change and the hydraulic characteristics of Poyang Lake,but will increase the water age of Tongjiang River area and central lake area above the dam site.The above conclusions can provide some theoretical reference for the transformation of Poyang Lake water environment. |
