| The Manas River Basin is located in the arid regions of northwest China.Water resources have a very important impact on the economy,society and ecology of the region,and are called“lifelines”by local people.Glacial meltwater is the main runoff source in the Manas Inland River Basin.With global warming,the uneven spatial and temporal distribution of precipitation and the accelerated ablation of glaciers have changed the spatial and temporal distribution of water resources in the region.Wetlands are sensitive factors and indicators to ecological environment changes.Significant effects will be made due to its presence and scale which also reflect changes to the environment.So with global warming,It is very important and special to study response of glacial meltwater as the main recharge of wetland to glacier change.Therefore,based on landsat images and MODIS images from 1976 to 2017,this paper uses time-space fusion,target recognition,statistical analysis and other advanced technologies and space-to-ground observation methods to extract and analyze the snow in the Manas River Basin for nearly 20 years.The shading glacial area was decomposed and the spatio-temporal variation characteristics of glacial ablation were analyzed.The object-oriented classification method was used to extract the total wetland area of the seven periods from 1976 to 2017,and the temporal and spatial variation characteristics of the wetland area were analyzed.Based on the 1958-2017 precipitation and temperature time series datasets observed at various stations in the Manas River Basin,the characteristics of climate change in the Manas River Basin are discussed.Based on the above data,the effects of climate change on glacial ablation and the response of wetland changes to glacial ablation are analyzed,and the effects of human factors on wetland changes are considered.Through the above analysis and research,the following conclusions are drawn:(1)The total area of the Manas glaciers in the past 40 years has been decreasing,from 3,746.64 km~2 in 1976 to 556.13 km~2 in 2017.The total area of glaciers has decreased by 3,913.51 km~2,and the average annual retreat rate is 77.89 km~2/a at the same time,there was a large change in area in 2002,2003,2006 and 2009.(2)The area change curves of rivers and marshes in the basins in the past 40 years are gradually decreasing.The lake wetlands and constructed wetlands are generally on the rise,and the total wetlands are slowly decreasing at a rate of 1.59%/a.The lake wetlands and constructed wetlands have the strongest changes.(3)Using the data series of precipitation and temperature time series from 1958 to2017,the analysis shows that the annual average temperature and annual cumulative precipitation both show an upward trend,but the correlation coefficient of the pearson correlation test is-0.497,and the temperature and year are obtained.There is a significant negative correlation between the minimum glacial areas,indicating that warming is an important reason for the melting of the annual glaciers.(4)From the point of view of attribution analysis,although the theoretical increase of glacial meltwater may be beneficial to the development of downstream wetlands,the monitoring data indicates that there is no significant relationship between glacial area and wetland area change;human activities are the dominant factors causing recent regional wetland changes.The increasing population and economic development in the study area lead to the increase of water consumption and the continuous decrease of water resources in the river;The increase of glacial melt water,the increase of annual precipitation and the rapid inflow of river water play a decisive role in the expansion of lakes.Due to the increase of human economic activities and the weak awareness of protection,the swamps and wetlands are threatened.Artificial wetlands are constantly expanding due to the construction of reservoirs,canals and other water conservancy projects,as well as the reclamation of irrigated areas and oasis. |
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