Ecological Environment Impact Of Hydropower Development In The Middle And Lower Reaches Of The Qingjiang River

Large hydropower projects are often built in ecologically fragile areas,which will not only create huge economic benefits,but also stress the ecological environment system.How to accurately analyze and evaluate the impact of water conservancy projects on the ecological environment is of great significance to the protection and management of regional ecological environment.At present,the research area is concentrated on the main river basins,mostly on the scale of single project and local area.Due to the different characteristics of river basin and the development mode of hydropower station,the ecological evaluation index system has different emphases,and research results are lack of universality.Taking the middle and lower reaches of the Qingjiang River as the research area and the overall impact of the cascade development as the research direction,based on the RS and GIS technology,combined with the principle of landscape ecology,a multi-disciplinary and multi method complementary evaluation mode is established.It is found that the introduction of RSEI to the comprehensive evaluation of the ecological environment in the hydropower development zone is convenient and practical,and finally come to the protection countermeasures.Conclusions are as follows:(1)After the development and operation of Qingjiang River Basin,30.88%of the urban and rural industrial and mining residential land and 1.83%of the cultivated land have been flooded,which promotes the expansion of the city and brings about migration problems.Also the hydropower cascade development has accelerated the mutual transformation of different land use types in the region,making the land use structure enter a rapid adjustment and unstable stage.(2)Ecological restoration and degradation coexist during hydropower construction,and the overall landscape is in an unstable state:the Shannon’s diversity and evenness index continued to increase,with the change rate of 5.34%and 5.48%respectively,and the impact of vulnerable landscape was strengthened.The degree of landscape fragmentation increased by 40.48%,and the contagion index decreased by3.76%,so the connectivity became poor.The average patch shape index increased by2.31%,and the patch shape became more complex.The variation coefficient of patch area increased by 25.72%,and the landscape stability decreased.(3)To some extent,hydropower development affects the intensity and change direction of soil erosion:after the completion of the cascade hydropower stations in the lower reaches,the average erosion modulus of the study area decreased from1789.14 t/(km~2·a)to 1049.89 t/(km~2·a),with a decrease of 41.32%,the state of soil erosion is relatively alleviated,and the areas with poor soil erosion are mainly distributed along the main and tributaries of the Qingjiang River,the northeast of Changyang Autonomous County and the west of Yichang city.However,after the completion of the water elevator,the average erosion modulus of the study area increased to 1558.11 t/(km~2·a),with an increase of 48.41%,the soil erosion state tends to be worse,and the areas with enhanced soil erosion are mainly distributed in Badong County,Changyang Autonomous County and the west of Wufeng Autonomous County around the Shuibuya Hydropower Station.(4)By introducing RSEI and discussing its adaptability in the Hydropower Development Zone,this paper analyzes the spatiotemporal change of the ecological environment in Qingjiang Hydropower Development Zone from 1987 to 2015:The RSEI of the middle and lower reaches of the Qingjiang River in 1987,2004 and 2015were 0.443,0.664,0.515,showing a trend of first rising and then declining.The ecological environment improvement areas are mainly distributed in the low hilly areas and flat plain areas,while the ecological environment degraded areas are mainly distributed in the water conservancy hubs and their affiliated reservoir areas,the karst mountains along the coast,and the hilly areas where the Qingjiang River afflux into the Yangtze River.The ecological environment is most closely related to the MASVI and the NDSI.The average correlation of the 3 stages between ecological environment and these two indexes is 0.879 and-0.916 respectively.Improving vegetation coverage and controlling bare and dry surface are the keys to the environmental restoration of hydropower construction areas.