Ecological And Environmental Impacts Of Major Hydropower Projects In The Qinghai-Tibet Plateau

As the third pole of the earth,the Qinghai-Tibet Plateau has its unique geographical environment and climatic characteristics.The ecological type structure is simple,the regional ecological vulnerability is high,and it is vulnerable to global climate and environmental changes.It is a sensitive area for global climate change.In recent years,under the dual factors of global climate change and human activities,the Qinghai-Tibet Plateau has presented problems such as reduced ecosystem stability and increased resource and environmental pressures.Since 2000,hydropower energy development in the Qinghai-Tibet Plateau has entered the fast lane,and more than 20 large-scale hydropower stations have been planned to be built in three hydropower energy bases.The various effects brought about by the construction and operation of large-scale hydropower stations have been magnified on the Qinghai-Tibet Plateau.In-depth systematic research on these effects can not only provide useful decision-making reference for the construction of plateau ecological barriers,but also provide useful reference for hydropower development in the region in the future,and provide reasonable long-term healthy and sustainable development solution for the region.Based on the meteorological data from 1998-2017,the normalized vegetation index raster dataset and the data of the land use types from 1980 to 2015,this paper analyzes the pattern change of landscape pattern in the construction of major hydropower projects,regional temperature and precipitation changes before and after the completion of the power stations and the spatial distribution pattern of the growth vegetation on the upper and lower banks along the dams.Based on landscape pattern indicators,climate change trend linear tendency estimation model,and vegetation decadal raster dataset,the current status of construction and operation of major hydropower projects in the Qinghai-Tibet Plateau and its ecological impacts in these three aspects are quantitatively analyzed and the internal mechanism of action is explored,mainly draws the following conclusions:(1)The development of hydropower energy has caused the waters in the upper reaches of hydropower stations to increase to different extents,with a maximum increase of 96%,which has little impact on the water area of the whole basin.(2)The hydropower energy development zone has formed a labor gathering effect that meets the energy needs of regional development.During the study time interval,while the number of urban construction land plaques in the basin decreased,the area increased significantly.The original small-scale settlements were successively developed into urbanization,and the urban expansion trend was obvious.(3)After the completion of the hydropower station,the area of cultivated land has decreased to varying degrees,and the upstream water level uplift and population migration are the main factors.(4)The temperature in the affected area of the hydropower station has a clear upward trend,the precipitation is more uniform,and the reservoir area is the main factor for the change of regional temperature and precipitation.(5)The vegetation before the dam was more sensitive to temperature changes.After the dam was built,it was more sensitive to the change of precipitation.After the dam was built and the vegetation coverage increased significantly.(6)With the increase in the operating years of hydropower stations,the difference in vegetation between the upper and lower reaches of the dam has expanded year by year.On the whole,hydropower energy development activities have limited impact on the ecological environment of the Qinghai-Tibet Plateau,and have a significant effect on regional economic development.Natural changes are still the main driving factors for the ecological environment changes in the Qinghai-Tibet Plateau.