Hydrodynamic Research Of Poyang Lake Based On The EFDC

Poyang Lake, as China’s largest freshwater lake, has a very big impact onecological economy and security of Poyang Lake and the whole basin of the YangtzeRiver, and also occupies a very important position in China’s economic construction.Since Lake’s hydrodynamic research constitutes the basis of the studies of waterenvironment, this paper aims to simulate and analyze hydrodynamic characteristics ofPoyang Lake and its related information in virtue of the EFDC.The geometric model of Poyang Lake, based on the measured data in2008, isfirst established, and as a foundation used to build up a set of models for variousanalyses, including hydrodynamics, temperature, dye and water age, and wind. Themain results obtained are listed as follows:Lakes water level changes are significant differences in the wet and dryseasons. The average water level in the lake’s average water level gets to17.2m in thewet season but just13.3m in the dry season. The surface area and volume, hydrauliccharacteristics of the lake in different periods are quite different, especially in the wetseason reflow from the Yangtze River to Poyang Lake occurs.During the dry season when the water temperatures at the entrances of “FiveRivers” are lower, the overall temperature distribution in the lake is more uniform; butin the wet period, the same lower temperature at the entrances of “Five Rivers”, thewater temperature distribution is uneven in the lake, and gets a significantly highervalue in the northeastern bay because the water exchange is slow there.The water from “Five Rivers” flow into different areas of the lake and affectsthe exchange capacity of the water bodies. Taking the Gan River as an example, itdoesn’t flow toward the northeast bay according to the terrain but to the north area tomix with other rivers at the center main channel to the Yangtze River due to the waterdriving force from north to south, which makes Gan River influence20%-30%area ofthe whole lake. Poyang Lake has stronger exchange capacity of water body, which isconsistent with the seasonal water features, but due to the jacking and reflow of theYangtze River in the late wet season this capacity decreased significantly.The water level and lake surface velocity change along with the wind but theamount of change is small. In the meantime, the wind will cause vertical mixing, andvertical velocity at the boundary of the lake, which would be quite different as the wind takes effect.The above multi-analysis on the water environment of Poyang Lake show that:the water level and water flow, as two fundamental factors in the hydrodynamicprocesses, undergo significant changes due to various hydrodynamic factors (inflowsof “Five Rivers”, reflow, wind, etc.) and time effects, especially result in theperformance of “high water level likes a lake, low water level likes a river”. By fullygrasp of hydraulic characteristics, such as water temperature, flow rate, water bodymixing and switching, and so on, can provides strong technical support for theconstruction of Poyang Lakes and its sustainable development.