Migration Analysis Of The Middle Tarim River In Xinjiang,China

Human activities have caused great changes to the natural environment of river systems since the Anthropocene.The ecological environment of the Tarim River had been destroyed and a large number of vegetation cover had suffered degradation because of unreasonable water use in southern Xinjiang of China As the largest inland river of the country,its dynamic change is related to the sustainable development of the regional economy and society.This thesis takes the middle reaches of the river as an example to study its migration and driving factors hereof,so as to provide useful reference for the comprehensive management of the river system.In order to reveal the process of river dynamic change,this paper carried out a series of preprocessing on Landsat images dated 1970 s,1990,2000,2010 and 2020.The centerline of the river-course in each period was vectorized by visual interpretation,and the river migration rate,river width and sinuosity index in different time periods to reflect the process of river migration were calculated.The precise point positioning(PPP)approach was employed to visualize the three-dimensional velocity field in the study area to reveal the crustal movement using 256 long-term Global Positioning System(GPS)station data.At the same time,the standardized precipitation index(SPI)using 50-year monthly precipitation data from 38 weather stations was calculated to reflect the climate change process and the frequency of extreme climate change events in the study area.In combination with field investigation,the driving causes of river migration were explored and here are the main conclusions obtained:(1)From 1970 s to 2020,the middle reaches of the Tarim River(Yingbazha-Qiala)moved 81.5 m on average from southwest to northeast at the speed of 0.36 ～ 5.79 m/a.(2)The three-dimensional(3D)velocity field visualized by GPS data showed that the uplift speed of Kunlun Mountains and Altun Mountains is faster than that of Tianshan Mountains,and the Tarim Basin has been moved slowly towards the northeast at a speed of about 30 mm/a.Composed of the Precambrian basement,the Tarim Basin is a hard block and has been tilting to northeast.(3)The results of the SPI analysis show that the river ecosystem interacts with the climate change of the macro environment.The climate is wetter after 2002,and the mobility and runoff of rivers have increased compared with that before 2000,indicating that climate change has an impact on the river migration;(4)Combined with remote sensing images and field investigation,the ancient river continuously migrated from south to north before 1960 s,which is consistent with the results of the three-dimensional velocity field derived from the GPS data analysis.Before the Anthropocene,crustal movement seemed to be the main factor leading to the migration of river channels from south to north.The climate in the Tarim Basin appears to have become more humid in the last two decades,and the impact of human activities has increased since the Anthropocene.Therefore,human activities and climate change might have been both playing an important role since 1960 s.