Study On The Environment Change Of Chaohu Drainage Area Based On Remote Sensing

Chaohu , a lake located in the middle of Anhui Province, with the water system to left bank of Yangtz River, has its drainage area of 13486km2. Due to the analyses of boring samples, the cardinal stratum of lake-bed is mainly composed of Xiashu loess in the late Pleistocene, so its possible age is no more than 12000 years. Researches show that increasing population and economic process render a great pressure upon Chaohu's eco-environment after foundation of new China. Since 1980's, because of deadly destruction of vegetation, it occurs fast soil erosion and eco-environment becomes worse and worse, resulting in a great change of structure and function of eco-system around the valley. This paper analyzes the environment change of Chaohu from its initiation not only with the help of spatial analysis of GIS but also with the comparative study of RS images, relief maps, Geological map, historical preference, chorography and etc. It emphasize the chain reaction of vegetation destroy—water and soil erosion-lake's filling up—lake's dieing out as well as the disturbing process on hydrology and ecology of Chaohu from water installation. Using the inner relativity between land eco-system and aquatic ecology of the lake, the paper put forward some reasonable plans to improve eco-environment of Chaohu. The paper fabricates its contents as follows: For Landsat TM data has rich information, we analyze the image brightness curves of typical objects in Chaohu. The optimal combination bands for TM image interpretation are TM4,TM3,TM2 assigned with R, G and B primitive color respectively. Based on image interpretation results, we establish the classification system for Chaohu drainage area and classify the TM image of 1987 and ETM image of 2000. Using remote sensing post-classification dynamic change monitoring method, we get the change of Chaohu's eco-environment for resent ten years. For example, lakeshore landslip, lake has been filled up, forest and tilth has been destroyed, water quality has gone to bed etc. The reasons for the environment change of Chaohu are mainly attributed to human's disturbance. For example, people build sluice gate which effectively transforms the hydrological characteristics, drives its regulating function withered, makes shoals' structure and amounts stagnant, contaminates water body and brings the lake supernutrition as well. Inning shrinks the lake's area , weakens its capability to regulate floods and pushes the lake ageing. On the other hand, destruction of forest, intensive usage on plain land will inevitably lead soil quality descended and silt lakebed more. In the end of this paper, we suggest some reasonable plans to improve eco-environment of Chaohu such as to adjust the structure of agriculture, to plant trees, to constitute the manage system of water function section, to control the contamination gross, to dominate the water level of Chaohu etc.