Traits and Dynamic Changes of the Aeolian Sandy Land in the Source Region of the Yarlung Zangbo River in Tibet

The source region of the Yarlung Zangbo River originating from the Chamyungdung glacier on the northern slope of the Himalayas is one of the highest river sources in the world.Its ecological and environmental quality plays an important role in the water conservation function and the ecological security of downstream areas,such as the cities of Shigatse and Lhasa.The aeolian sandy land has developed obviously,as the climate is dry,the soil is poor and the environment is fragile in this region.This paper analyzed the distribution characteristics of aeolian sandy land and its dynamics change in the source region of the Yarlung Zangbo River by interpreting the past 20 years' Remote Sensing(RS) images of three periods,that is,1990,2000 and 2008,and matching it with the DEM data of this region using the technique of RS and GIS technology.The purpose is to illustrate the current situations correctly and find out the evolution tendency of the aeolian sandy land in the source region of the Yarlung Zangbo River.It was shown that: 1)The area of aeolian sandy land in the source region of the Yarlung Zangbo River was 1376.22 km2 in 2008,including fixed sandy land which accounted for 36.03%,semi-fixed sandy land which accounted for 28.10%,shifting sandy land which accounted for 9.39%,bare gravel sandy land which accounted for 14.64% and semi-bare gravel sandy land which accounted for 11.84%.2)The area of aeolian sandy land in the source region of the Yarlung Zangbo River was 1281.78 km2 in 1990,1359.7 km2 in 2000 and 1376.22 km2 in 2008 respectively.It had increased by 94.44 km2 in the nearly 20 years.3)The aeolian sandy land was mainly distributed at the elevation ranging from 4600 m to 4800 m,or 76.13% of the total.From the view of the aspect,the aeolian sandy land was mainly distributed in the flat area,or 56.97% of the total sandy land,following by the southwest aspect and south aspect,being 11.20% and 8.66% respectively.4) Abundant sand materials and strong wind blowing are the potential conditions for aeolian sandy land development.The global climate has been getting warmer in the past 20 years,and the higher temperature favored to the further development of aeolian sandy land in the study area.