Study On Eco-hydrological Process And Regulation Countermeasures In Typical Wetland Of Poyang Lake Under Changing Environment

With the climatic change and the rapid development of society and economy, hydrological regime and water environment in Poyang Lake have undergone great changes,which it can affect wetland ecosystem and ecological security in Poyang Lake directly. To maintain the ecological functions and ecological security in Poyang Lake, research of eco-hydrological process and regulation countermeasure in typical wetland under varying environment, has an important theoretical and practical significance. The main contributions of this study were summarized as follows:l.With measured annual runoff and annual sediment load data during1956-2008,studied the temporal and spatial distribution characteristics of Poyang lake watershed runoff and sediment load in Poyang Lake were analyzed.Using Mann-kendall test method, in this paper the main cause of the runoff and sediment variety of Poyang Lake from the aspects of watershed rainfall, water, reservoir block sand, the three gorges water storage, soil erosion and its control were discussed. The reasons indicate that decline in precipitation of Poyang Lake Basin has a significant impact on the decrease of inflow and outflow runoff to lake for nearly a decade, and reservoir lag sand is primarily reason for reducing the inflow sediment load to lake, and variety of outflow sediment load to lake was mainly affected by reservoir group in the upstream of Poyang Lake Basin and sand mining in recent years.2.Based on analysis of variation of the total runoff into Poyang Lake, the drought-flood abrupt alternation was analyzed using the Long-cycle Drought-Flood Abrupt Alternation Index (LDFAI). The results show that the alternating cycle from drought to flood and from flood to drought exists between Apr-May and Jun-Jul in the long term. And the interval from drought to flood and from flood to drought is becoming shorter and shorter in the21st century, which’means the oscillation of the alternation of drought-flood is intensified.3.The hydrologic processes determine the structure and function of ecosystems of Poyang Lake wetland, of which the water level change is the most important factor effecting its ecosystem state changes. CoupModel Model was used to simulate respiration amount (carbon) of wetland typical vegetation from1990to2011, and then combined with daily water level of Xingzi station in Poyang Lake with corresponding period, the relation between Poyang Lake wetland biomass and the water level of Poyang Lake was studied. The reason show that when the water level is greater than14m, the total respiration amount is significantly smaller, when high water level continued, the total respiration amount gradually weakened; within a certain range, and extended duration of low water level conditon, the cumulative plant respiration amount shows a gradually increasing trend; higher maximum annual amplitude level, the smaller the cumulative amount of plant respiration, indicating that the more severe level changes within a year, the more goes against the growth of wetland vegetation; study on the relation between the highest level and the cumulative effect of plant respiration show that when the highest level higher, cumulative effect of plant respiration lower. When the maximum water level is lower, the greater the cumulative effect of plant respiration. The relation between average water level and cumulative amount of plant respiration also showed the same pattern.4.The CoupModel-ANN eco-hydrological model is established, which can simulate the relationship between the water level of Xingzi station and respiration amount (carbon) of wetland typical vegetation, using this model in this paper,we discussed the effects on wetland conservation of different scheduling scheme of Poyang Lake hydraulic project. Meanwhile, Using CoupleModel-ANN model, vegetation respiration amount was predicted in different level programs of Poyang Lake hydraulic project, compared with average vegetation respiration amount from1990to2011in normal year, which were simulated by CoupModel, We came to the conclusion that the suitable water table is10-14.5m for the restoration and protection of wetland ecosystem in the study area.