| The Three Gorges Reservoir area, with a total length of 645.29km2, 1084km2 of water area, and a total capacity of 44570 million cubic meters along the main stream of the Yangtze River and Jialing River, is one of the most important resources of drinking water in China in the future. With the completion of its experimental impounding on Nov.4th 2008, its water level reaches 172.8 meters, which would rise to 175 meters in 2009( Factually, it has already finished on Sep. 28th 2008). Since the construction of the project, something dramatic has been happening to the land and the ecological system. As a result of its storing clear water and releasing sediment operation mode, a fluctuating zone, with a stream fall amounting to 30 meters, has taken shape in areas along the river. Simultaneously due to the operation mode of low water level in summer and high in winter, the fluctuation of reservoir water level in these areas is opposite to that in the natural state.The altitude of the fluctuating area is from 145m to 175m. The upper region (170m to 175m) has a relatively shorter submerged time than the lower region (145m to 155m). The area faces with a sharp increase of the density of population and activities of the human being. Thus the Three Gorges Reservoir area is confronted with severe ecological problems, such as irrational development and utilization of land resources of the fluctuating zone, its natural disaster, water loss and soil erosion, water pollution, water environmental depravation and so forth. The objective and scientific assessment of the possible ecological risks may provide a theoretical basis for harmonious development between economy and eco-environment of the fluctuating areas in Kai County.Under the support of the Natural Science Foundation of Chongqing, this research tries to make use of such technical means as GIS, GPS, and RS to collect the remotely sensed data of the reservoir area, the foundation geographical data, and other related data from the field reconnaissance. Taking the land use of the fluctuating zone in Kai County as a typical case and with its environmental settings put into consideration, this study seeks to put forward a series of models for the development and utilization of land, and tries to carry out ecological risk assessment of land development and utilization by using the Relative Risk Model (RRM).Based on different sea level elevation of unsubmerged area, it divides the Kai County fluctuating zone into 4 risk assessment districts: district I <150m, district II 150-160m, district III 160-170m, district IV 170-175m. A contrastive study of the ecological risks in different districts can help to grade the ecological risks and form a spatial figure. Species diversity, habitat quality, landscape pattern are regarded as ecological appraisal endpoint, according to the following 7 factors: description and formation of the problems; risk suffer analysis and the choice of ecological endpoint; risk sources analysis; conceptual model and its analysis program; risk exposure and imperil analysis; risk attribute; risk management, etc. To adopt the conceptual model of exposure and respond route between risk source, pressure, habitat change, ecological end point, it further introduces two indexes: pressure density and habitat abundance loss. Finally through comprehensive calculation product of pressure density, habitat abundance loss, exposure coefficient, respondence coefficient, the latent risk value is reckoned on the basis of different risk source types, different habitat change, different ecological endpoint and different risk sub-districts.The project district is then divide d into4 risk grades: 0-2 (the first level),2-4(the second level), 4-6 (the third level),6-8 (the fourth level) followed by a risk rating figure. The results of the RRM shows: (i) The land of the fluctuating area of the County is mainly used as arable land and water masses, which contribute a lot to the economic development in that area, but face with a relatively higher ecological risk. (ii )The area with an altitude below 150m and between 150m to 160m falls into the first level and medium risk district respectively. The area with an altitude of 160m to 170m also belongs to medium risk district, but it has a larger size of utilization area, and accordingly has a relatively higher risk value ratio and degree of risk. (iii) The area with an altitude of 170m to 175m possesses the longest unsubmerged time, adding its chance of land use. Thus its possible risk, risk value and degree of risk are all among the highest.In conclusion, based on the research of the Kai County, ecological risk management strategy of land use in fluctuating area is proposed, aiming at providing a theoretical basis for evading land use ecological risks of fluctuating Reservoir areas. Its important exemplary role and practical significance is also of great importance.
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