| The upper reaches of the Min River is located in the Qinghai Tibet Plateau and the Sichuan basin transition zone with deep valleys,mountains and canyons and many large undulating surface,the relative elevation is 1000 meters,because of the water resources advantage,the hydropower development continues to expand,the scale of construction and operation of hydropower will bring benefits to the economy and the impact of ecological environment.Therefore,this paper takes the cascade hydropower development of the upper reaches of the Min River as the research object.Through the construction of the evaluation index system,the quantitative and qualitative analysis is carried out on the impact of the cascade hydropower development on the geological and ecological environment,and the feasibility of the theoretical evaluation method is used to reveal the impact range of the cascade hydropower development on the geological and ecological environment.It provides a basis for the sustainable and sound development of the regional ecosystem.The main progress and conclusions of this article are as follows :(1)Hydrological changes and information extraction of land use in the upper reaches of Min River.The study look Zagunao River Basin on the upper reaches of the Min River as the object of analysis of typical sub watersheds.Looking Sangping station in 1988-2008 years hydrological data as the foundation,the results show that the Zagunao River basin runoff decrease,wet year and dry year alternately appear;average annual sediment is universal a downward trend;the frequency of geological disasters increase.we choose 1994,Landsat TM,2007(Landsat TM)and 2014(OLI)multi band remote sensing image as basic data.By the way of supervised classification,the upper reaches of Min River can be divided into 5 land use types: cultivated land,unused land,woodland,water area,and urban and rural building land.The direct or indirect influence of engineering construction on land use change is analyzed.The classification results show that with the continuous expansion of hydropower station scale,the vegetation coverage rate in the upper reaches of Min River is decreasing,the area of unused land is enlarged,the arable land is reduced,and the construction of urbanization is more concentrated.(2)Land use types of classification based on the theory of landscape ecology and the landscape pattern dynamic change analysis,which selects the number of patches,patch area,NP CA PD,patch density,largest patch index LPI and the proportion of landscape PLAND;perimeter area fractal dimension(PAFRAC,interspersion and juxtaposition index(IJI),similar to the adjacent the percentage(PLADJ),aggregation index(AI),contagion index(CONTAG),the landscape connectivity index(COHESION),Shannon’s diversity index(SHDI)and Shannon index(SHEI)and other indicators of land use types as the quantitatively analysis in the upper reaches of Min River and the results show that the construction of hydropower station,the expansion of the number and the area of the reservoir directly or indirectly led to the upper reaches of the Min River pattern changed greatly.The number of patches of woodland and cultivated land,unused land area is decreasing,and the expansion of urban construction land area;the landscape perimeter area fractal dimension index is less than 1.5,indicating disturbed by human activities is relatively large;interspersion and juxtaposition index,similarity and aggregation are larger;degree of landscape change of cultivated land connection is larger;the landscape diversity in Shannon index and Shannon’s evenness index decreased,indicating to the region landscape diversity affects the construction of hydropower station is relatively large.The expansion of unused land area is serious,the area of cultivated land is reduced,and the construction of urbanization is concentrated.(3)The study area use RUSLE(revised universal soil loss equation)model to estimate the soil and water loss caused by the direct or indirect Hydropower Station Construction in upper reaches of Min River.By computing three different periods of rainfall factor R value,the factor of soil K value,DEM slope length the L value and S value of slope and vegetation cover factor C and factor P value of soil and water conservation in grid in the year of 1994,2007,2014,and using GIS spatial overlay analysis,we get the amount of soil erosion spatial distribution map based on grid units in the study area,the figure shows the soil erosion are constantly expanding in the area or degree.(4)We will further use remote sensing and GIS technology,and combined with the basis of previous studies to acquire soil and water loss in extraction,strength grade,vegetation index,soil index,humidity index,heat index evaluation index system,and use graph overlay method to analysis the changes of environmental quality in comprehensive evaluation research area and the effect on the ecological environment.The results show that the environmental quality of the study area is relatively poor,which indicates that the construction of cascade hydropower stations has a great impact on the environmental quality of the region.At the same time,the cascade hydropower development in the upper reaches of the Min River has destroyed the forest and cultural landscape,the area of the arid valley is enlarged and the destruction of the surface is serious,and bring a certain impact to the national culture of the region. |
