Groundwater And Surface Water Interactions And Their Ecological Effects Of The Gan River Delta

Poyang Lake is the largest freshwater lake in China, is the world’s important wetlands and migratory birds reserve. Due to population growth and various human activities such as afforestation, the ecological environment of Poyang Lake has been influenced. Especially since 2003, that aroused wide public opinion about the Three Gorges reservoir caused Poyang Lake low water level. And the academic schools of thought contend about influence of proposed Poyang Lake water conservancy hub to ecological environment. Comparing hydrological characteristics of Poyang lake before and after the Yangtze Three Gorges construction, it is imperative to seek the scientific method to study the effect of the Three Gorges to poyang lake hydrological regimes. Gan river delta is the largest and most complete development of Poyang Lake, it is of great significance to study groundwater and surface water interaction and master the Poyang Lake region of hydrological and ecological process. That has an important position for judging the feasibility about proposed hub based on groundwater environment of Poyang Lake.In this paper, numerical simulation, intelligent calculation, statistical analysis and other methods have been comprehensive used to study above problems systematically. Wavelet analysis method was used to seek similar hydrological series about rainfall. Hydrological characteristics of Poyang Lake was comparated analyized before and after of the Three Gorges construction. The result is the drought period extended and advance, during dry initial water level is lower, but at the end of season water level increased slightly.3D groundwater flow model of the study area is established based on the theory of water balance. Analyzing water balance in the study area, the elements relationship of groundwater recharge and discharge was discussed. Combining with the regional groundwater and surface water dynamic relationship, that was analysised of interaction between groundwater and surface water. It is mainly that groundwater recharge surface water of the study area. Only that when the water level of river was high groundwater recharged from surface water. Weak interactions between groundwater and surface water, and groundwater runoff were lagging. Support vector machine was used to calculate the Poyang Lake water level of each station after hub control. The impact of Hub to groundwater was calculated combined groundwater movement model. The overall result was groundwater rised 0～3 m during the phase of Hub controlling. And impact area within 3 km from the banks of the river. The intensity was weak about groundwater runoff alternately of the study area. The equilibrium results from the model that the groundwater excretion decreased by 21.55% during drought period, groundwater recharge reduced 21.54% in plentiful, and groundwater flow into a new equilibrium. It was Statistical analyzed that the relationship of Poyang Lake water level and coverage grass land, and the characteristics of groundwater depth and vegetation distribution. Results showed the emergence grass land showed of obvious phenomenon when water levels declined grass land appeared, while water level raised grass land disappeared. And a significant difference was found about groundwater depth in different vegetation zone. There’s a certain hydrological compensation of groundwater to surface water. The ground water is mainly influenced the soil water content and salinity by the depth and total dissolved solids of the ground water, which affect the distribution and growth of the surface vegetation.This article is first to combine groundwater numerical simulation technology with artificial intelligent algorithm such as neural networks. It is the first time to research ecological environment effect from groundwater of wet regions. Poyang lake corresponding scientific problems have been solved, such as Poyang Lake interaction between surface water and groundwater, proposed construction of Poyang Lake project impact to groundwater and ecological environmental, the three gorges reservoir influence the hydrological regimes of Poyang Lake. And certain achievements and unique insights have been obtained.