Variation And Potential Hazard Assessment Of Lakes Along Xinjiang-Tibet Highway

In the context of global warming,the lakes in the Qinghai-Tibetan Plateau region have responded significantly to climate change,and their area has been expanding since2000.The changes of lakes not only have significant feedback effects on the surrounding hydrological and atmospheric processes,but also have great impacts on human production and life,such as the expansion of lakes near roads/railways and even flooding of some road sections to affect transportation.Especially in high mountain and polar regions,the number and area of glacial lakes change significantly,which has an impact on regional water resources management,coupled with the frequent occurrence of glacial lake outburst floods(GLOFs),which seriously endanger the safety of people’s lives and property in downstream areas,and has destructive consequences on infrastructure such as roads,bridges and hydroelectric power stations.GLOFs are more prominent in the Qinghai-Tibet Plateau region,and it is recorded that there are 33 glacial lakes having experienced 37 outbursts in Tibetan region,resulting in varying degrees of casualties and property losses.Due to the complex terrain,sparse population,and underdeveloped economy of the Qinghai-Tibet Plateau,transportation infrastructure plays a crucial role in connecting the region with the outside world and promoting its social and economic development.The National Highway 219(G219),also known as the Xinjiang-Tibet Highway,is located in the western of the Qinghai-Tibet Plateau and is of great importance as the only channel connecting Xinjiang and Tibet.In recent years,lakes along the Xinjiang-Tibet Highway have been expanding and approaching parts of the road,posing significant safety risks for transportation.Coupled with increased glacial lake outbursts flood risks in the region,the potential hazards to the highway have become more severe.Using NDWI combined with the triangle threshold algorithm to extract lake boundary data from Landsat ETM+images in 2000 and Sentinel-2 MSI images in 2022,we analyze the lake evolution characteristics to identify the lakes with potential threats to the Xinjiang-Tibet Highway,including non-glacial lakes with rapid expansion and glacial lakes with outburst potential,and to identify the road sections that may be affected,provide a scientific basis for the understanding of lake change patterns and for road safety prevention and control.The results show that:(1)There are 1805 lakes with area greater than 0.01 km~2 along the Xinjiang-Tibet Highway in 2022,with a total area of 2398.24 km~2.Of these,1446 are glacial lakes with an area of 138.54 km~2,and 359 are non-glacial lakes with an area of 2259.71 km~2.The region is dominated by lakes with area less than 0.6 km~2,most of which are distributed in the southern slopes of the GangdisêMountains and the northern slopes of the Middle Himalayas.There are four medium-sized lakes in the study area,Longmu Co(110.32km~2),La-ang Co(251 km~2),Aksayqin Lake(282.85 km~2)and Mapangyong Co(416.91km~2)and a large lake,Pangong Tso(695.04 km~2).(2)From 2000 to 2022,both the number and area of lakes in the study area show an increasing trend.The number of lakes increases from 1762 to 1805,with 256 newly formed lakes and 213 disappeared lakes.The total area of lakes expands from 2214.49km~2 to 2398.25 km~2,with an area growth rate of 8.30%.Among them,215 lakes increased in area,416 lakes decreased,and 918 lakes remained stable.The number of lakes with areas between 0.01 km~2and 0.03 km~2 changed most significantly,from 786 to 915(16.41%).The increase in the number of lakes is mainly in GangdisêMountains and the Middle Himalayas,within an altitude range of 5500～6000 m.The increase in area of lakes is mainly in the GangdisêMountains and West Kunlun Mountains.The five lakes with area larger than 100 km~2 are located within an altitude range of 4000～5000 m and have expanded significantly in the last 22 years.(3)There are 7 expansive non-glacial lakes along Xinjiang-Tibet Highway have the potential impact on the road,including Pangong Tso,Longmu Co,Quanshui Lake,Lang Tso,Hongshan Lake,Kayi Co and Angla Co.These lakes continually expanding and gradually approach the Xinjiang-Tibet Highway.As their shorelines advance,they incessantly erode the roadbed or flow beneath it,combined with the freezing and thawing of lake ice,it is easy to cause roadbed instability or damage,resulting in collapse subsidence and other hazards.In total,11 road sections vulnerable to such impacts have been identified.(4)In 2022,there are 70 glacial lakes with outburst potentials in the study area,including 13 glacial lakes with very high outburst potential,24 glacial lakes with high outburst potential,13 lakes with middle outburst potential and 20 lakes with low outburst potential,accounting for 18%,35%,18%and 29%of the total number of dangerous glacial lake.These glacial lakes are concentrated in the altitude range of 4800～5800 m,mainly distributed in the Middle Himalayas and near the GangdisêMountains.There are6 sections of the Xinjiang-Tibet Highway where GLOFs can reach directly,as well as 3sections where GLOFs could indirectly impact the highway by joining with nearby rivers that are closer to the road.To reduce the influence of GLOFs on the Xinjiang-Tibet Highway and ensure its safe operation,measures such as rerouting,raising the roadbed and building water-proof dams could be adopted in combination with the actual situation.