Research On Land Use System Structure Of Water-level-fluctuating Zone In Three Gorges Reservoir

It's the fourth water storage in Three Gorges reservoir area in 2009, the water-level-fluctuating zone fully formed. The formation of fluctuating with the Three Gorges Reservoir, "store clean water and discharge turbid water", the water level will keep to 175 meters in winter and 145 meters in summer, which forms a water-level-fluctuating zone between 145 meters and 175 meters. The area of water-level-fluctuating zone in Kaixian County is the largest, so this paper choose one typicality-the water-level-fluctuating zone of Kaixian county as research area.Firstly, based on the basic data collection and field investigation, summarize the land use system of water-level-fluctuating zone in the Three Gorges Reservoir, and analyze the composition, characteristics and functions of land use system.Secondly, using the theory of Shannon entropy and fuzzy comprehensive assessment to analyze the land use structure of before the Three Gorges Project drawdown, then to analyze simulation of land use structure and compared the simulation and reality, Thirdly, explore the rationality of land use system structure in fuzzy comprehensive evaluation. The results showed as following:1) Defining the scope of land use system between 150 meters and 195 meters in the water-level-fluctuating zone in Kaixian. After the fourth water storage in Three Gorges reservoir, land use system in the water-level-fluctuating zone has fully formed, it is a special and open system.. The whole water-level-fluctuating zone include shore zone, fluctuating zone and water zone.2) The land use structure change of Shannon entropy:With the upgrade of reservoir water level, the entropy of land use system is increasing in Kaixian. The entropy of land use structure was 1.3294 in 2003, then increased to 1.4993 in 2009, the average annual growth rate reached 1.89%. It demonstrates the land use structure is high order relatively in2003, and land use disorder increased highly in 2009.3) Four hypothetical land use patterns showed:fluctuating zone of various modes of land use systems will experience a relative disorder to relative order, to the relative disorder of the change process. The land use structure entropy is in a minimum level in wetland protection pattern, indicating that the land-use system is order. And the land use structure entropy is bigger than other patterns in synthesize patterns, and the land use system is disorder. The cultivated land use pattern and forest land use pattern are bigger than wet land use pattern. Therefore, the wetland protection pattern is the best pattern in four simulation patterns. At the same time, it confirmed the importance of wetland protection in urban edge.4) The actual land use patterns:Because of the construction of the reservoir water level adjustment dam, the land use structure is changing. This is the "dam" pattern, the entropy value is 1.4124. Comparison of hypothetical patterns and the "dam" pattern:wetland protecting pattern> "dam" pattern> cultivated land use pattern> forest land use pattern> synthesize patterns. In other words, if choosing wetland protection patterns, the land use system in water-level-fluctuating zone is more orderly, and the "dam" pattern is more superior than the other three patterns.5) The analysis of fuzzy comprehensive evaluation results showed:If adopted cultivated land use pattern or forest land use patterns, the rationality of its comprehensive evaluation is a lower level; if adopted wetland protection pattern or "dam" pattern, the comprehensive evaluation is middle level. Although wetland protection pattern or forest land use pattern, the land use system of water-level-fluctuating zone is not reasonable, it's difficult to achieve very reasonable, so current "dam" pattern is acceptable.