The Water Environment Changing Features And The Ecological System Health Evaluation Of Hongze Lake Wetland

The health of wetland environment is receiving wide attention of scholars both at home and abroad currently. The Hongze lake wetland nature reserve in Sihong is the largest national wetland in Jiangsu Province. In recent years, the health of wetland ecological system has been greatly influenced by environmental changes and human activities. Therefore, it is especially important to study on the health condition of Hongze lake wetland nature reserve in Sihong county. Because water is an essential component of wetland, and water environment has a direct impact on the function and development of wetland, to analyse the feature and quality of water environment contributes significantly to the study of wetland ecological health.Through field investigation, data collection and sample analysis, data about the meteorology, hydrology, soil and vegetation of Hongze lake wetland are acquired. The meteorological factors and the changing features of water environment have been studied:the gray relativity between meteorological factors and water level of the lake, the space-time changing factors of water environment quality as well as the comprehensive water quality evaluation have been analysed. Based on the analysis, the theory and specific method of ecological system health have been adopted to construct the ecological health index system of Hongze lake wetland, so as to evaluate its health level comprehensively and quantitatively. The results show that: during nearly31years between1979and2009, climate in Sihong Area of Hongze lake wetland features a warm and wet tendency of a rising temperature, an increasing amount of rainfall and a decreasing amount of the amount of evaporation. Changes of water level in this area show a positive relation to humidity and rainfall, but a negative relation to temperature, the amount of evaporation and sunshine. The height of water level is closely related to temperature and humidity, two factors of climate, and the index is0.9978and0.9466. It is also related to the amount of rainfall to some extent, but shows a relatively less relation with the amount of evaporation and sunshine. From2009to2010, all the indexes of water environment present some change rules, and at the same time, relativity is shown among the indexes. Comprehensive evaluation of section water quality reveals that the proportion of water of V category is relatively large, and its average health level is0.4838which is also below0.55, which is still lower in abundant water period than in dry and mean water period. Indexes severely exceeding the provided standard are total phosphorus, total nitrogen. Total phosphorus deserves special attention, for it reflects that the water quality of Hongze lake is very poor and that eutrophication is quite serious. Fuzzy integrated judging indicates that the ecological system health of the whole wetland is0.5669, which means the system is vulnerable, under great pressure and highly sensitive. The health degree of human social environment index, which has most restrictions on the ecological system health of the wetland, is merely0.4876. Then follows the ecological feature index, which is only0.5645. The health degree of functional comprehensive index, which has the least restrictions, is0.6153.