Study On Land Use Ecological Risk Evaluation In Three Gorges Reaervoir Area

After stored water with the Three Gorges reservoir of the Three Gorges Project, the water level change affected the ecological environment deeply and showed the unstable state.it is a typical ecological fragile zone.That caused serious consequences to the ecological environment due to unreasonable land utilization and directly threated to the security of the Three Gorges Project.The sustainable development of social economy in the Yangtze River basin.Wanzhou Area is centered in the district of Three Gorges reservoir, and the Yangtze River flows through the whole Area. After reservoir impoundment, the submerged area is larger, and land use patterns and structure change seriously, so it is the typical Area in the Three Gorges reservoir Area.Taking wanzhou district as the research object, the data sources include the Landsat TM remote sensing data, social and economic data and environmental monitoring data of Wanzhou, build the evaluation index system based on PSR model, using the analytic hierarchy process to determine evaluation index weights, introducing the normal cloud model ecological risk of land use of Wanzhou Area,analysis the change rule and trend. Finally, using the grey model to predict the evaluation results the ecological risk on land- use, the results show that:(1) The land use type of wanzhou area dominated by forest land and farmland in the quantitative structure, forest and cultivated land area accounted for 93.9%; cultivated land, forest land, grassland area gradually reduced of the time changed. The area of construction land was increasing year by year, the cultivated land area changes is the largest, 35365 km2, construction land was the second. Forest land are mainly distributed in northwest and middle- mountain of southeast of the first-hand and low mountainous Area, the cultivated land are mainly distributed on the plain area of either side of the Yangtze river basin pingba, and low mountainous areas surrounding the cities and hilly area, the urban construction land mainly concentrated Yangtze river basin.(2) The change of ecological environment index in wanzhou area: the pressure of ecological risk has a rising trend,the proportion of fanning terra reduced somewhat.The proportion of construction land,agricultural non-point source pollution,the existing status of industrial pollution source,density of road network and population density increased, the road network density increased the sharpest, the proportion of 300% increased or more; The state of ecological variation was worse, patch density and the shape index values increased, the perimeter area fractal dimension,aggregation degree and average nearest neighbor distance decreased;The value of ecological response has increased, it caused by the index of comprehensive structure and the corresponding degree of water and soil.(3) The wanzhou area use the land to keep the ecological risk of land of low risk and medium grade. In the average level of risk membership, the risk of low and medium grade are significantly higher than other grades; In the evaluating index comprehensive evaluation value,10 indexes decreased, 6 evaluation indexes increased, the perimeter area fractal dimension, the corresponding degree of water and soil and the index of comprehensive structure mutations in situation, the ecological environment influence is bigger,it should focus on.(4) The land of wanzhou use the ecological risk assessment is a medium risk in the next three year. By building forecast model, the model through to 2015, 2016 and 2017 after testing to predict the ecological risk of land utilization, it is concluded that the three years risk level is medium risk.