内蒙古呼伦贝尔草原湖泊变化研究

内蒙古呼伦贝尔地区湖泊数量多,面积大,占内蒙古湖泊总面积的58%。近年来该地区湖泊趋于萎缩,但是已有研究主要关注大型湖泊,缺乏对该地区湖泊整体,尤其是小型湖泊(<1 km²)的研究。通过利用Landsat系列(TM、ETM+、OLI)卫星数据,参照该地区湖泊图集、湖泊名录以及Google Earth高清影像,分析了1986—2017年呼伦贝尔草原地区湖泊数量和面积变化;在此基础上结合气候和人类活动资料,讨论湖泊变化的影响因素。研究表明:近30 a呼伦贝尔地区湖泊显著萎缩,其中变化最为剧烈的是小型湖泊,新增5个,干涸19个,总面积减小超过30%。2000年前各类型湖泊面积均有增加,1998年降水量最大,湖泊面积相应达到峰值;2000—2010年湖泊面积呈萎缩趋势;2010年以后有所回升。将湖泊面积与气候条件(气温、降水量、潜在蒸散量)及人为活动因子(放牧强度、原煤产量、有效灌溉面积)进行相关分析发现,湖泊面积变化主要受人类活动的影响,气候变化的影响相对较小。

Three-decadal changes of lakes in Hulun Buir grasslands,Inner Mongolia

Lakes are important water reservoirs that play an important role in water supply and climate regulation,especially in arid regions.A large number of lakes are distributed across the Hulun Buir grasslands,which account for as high as 58%of the total area of lakes in Inner Mongolia,China.Subjected to significant climate change and intensive anthropogenic activities,lakes in the Hulun Buir grasslands have shrunk significantly.Shrinkage of the lakes in this region may accelerate grassland degradation and reduce the lakes’ecosystem services.However,long-term changes in the number and area of these lakes,especially the small ones(<1 km²),are poorly understood.Using the Landsat data(TM,ETM+,and OLI),in this study,we assess the changes in the number and area of lakes and their drives in Hulun Buir between 1986 and 2017.The assessment especially focuses on small lakes because they are more sensitive to environmental changes and have more widespread influences on livestock production compared to large lakes.We first used Google Earth Engine to analyze the Landsat surface reflectance data and extract the water body coverage of the lakes based on the normalized differential water index.Then,we explored the changes in the lakes and their possible driving forces over the past three decades.The results showed a significant shrinkage in the lake area during the last three decades with the most dramatic change occurring in small lakes.Specifically,the number and area of small and large lakes showed a significant decrease,whereas the decline in the area of medium-sized lakes was insignificant.The temporal change in the area of the lakes was nonlinear,showing an increase before 2000 and a decrease after 2000.A correlation analysis of the regional changes in the lake area with climatic factors(temperature,precipitation,and potential evapotranspiration)and human factors(grazing,mining,and irrigation)indicated that the areal shrinkage of small lakes was mainly due to an increase in the cropland area and water consumption by irrigation and that the impacts of climate change is relatively minor.The decrease in the area of large lakes was mainly caused by water consumption because of coal mining.In addition,the warmer and drier climate contributes to the shrinkage in the lakes’area.Due to an increase in the area of agricultural land and exploitation of groundwater for coal mining,water consumption in this region stayed at a high level.The findings of this study recommend the optimization of industrial structure,upgrading of irrigation systems,and improvement of coal mining technology to protect lakes from further shrinkage and achieve a sustainable supply of water resources.