近期亚洲中部高山地区湖泊变化的时空分析

亚洲中部高山地区湖泊是气候与环境变化的敏感指示器,湖泊面积与水位的变化客观地反映了该地区水资源的时空变化过程。充分认识高山地区湖泊变化的特征及驱动性因素,有利于正确评估气候变化和人类活动对湖泊变化的影响。本文针对高山地区缺乏观测资料的特点,利用遥感资料重建近期亚洲中部高山地区湖泊的水位及面积变化信息,并在此基础上分析了水位和面积对湖泊变化描述的敏感程度,分别从湖泊类型、区域分布和影响因素讨论了近期亚洲中部高山地区湖泊的时空特征。水位可以更好地描述高山湖泊变化的时空过程,10月份是中亚高山地区湖泊相对稳定的时期。对于封闭性湖泊而言,近期青藏高原北部地区的湖泊扩张明显,而天山中部的湖泊水位微弱上升或保持不变,而阿尔泰山地区的湖泊处于萎缩的状态,湖泊的变化与降水及冰川分布具有较好的相关性。吞吐型湖泊的变化按有无水坝呈两种变化趋势,出水口建有水坝的外流湖水位下降明显,而自然状态下的外流湖水位相对稳定,一定程度上反映了近年来过度向吞吐型湖泊引水与开发的趋势。

Spatio-temporal Analysis of Recent Changes of Lake Area and Lake Water Level at High Mountains in Central Asia

Inland lakes are major surface water resources in arid regions of Central Asia. They provide sparsely distributed but valuable fresh water resources for the fragile environments and human activities, which act as the essential components of the hydrological cycle and local ecosystems. Lakes in alpine regions are sensitive to natural changes, which can serve as an important indicator of global climate change and regional environment variations. Lake changes are mainly manifested by their level or area changes, which can provide evidence of spatial and temporal characteristics of regional water resource changes. Mapping these lakes and detecting their changes are therefore of great significance to understand the relevance of lake variations to climate changes, and they are also crucial to evaluating impacts of economic development on ecological balances. However, lake studies in these remote mountainous areas seem to be limited due to low accessibility and lack of observation data. Satellite remote sensing provides an efficient tool to analyze the status and variations in these lakes. In this paper, Landsat/CBERS were used to map lake area changes, and Jason, ICEsat/GLAS were employed to extract lake level information, forming a time series of level and area changes of 16 lakes over the past ten years. The spatial and temporal characteristics of lake level changes were also analyzed with information on glaciers and dams, so as to unravel the responses of level and area changes of different types of lakes to climate change and human activities. It is shown that remote sensing has a good performance of mapping lake level and area changes, and lake levels in October have good performance of describing the temporal processes of lake level changes. Glaciers are vital to alpine closed lakes, and the characteristics of level changes are classified into two modes based on glacier distribution: lakes in the northern Tibetan Plateau (the Kunlun Mountains, Karakorum Mountains, and the Pamir Plateau) and the middle Tienshan Mountain, both of which have glaciers in their drainage basins, and lake levels over these areas are increasing. While lakes in the Altai Plateau and Tienshan have no glacier-melting water to feed, lake levels are decreasing in these areas. Level changes of open lakes and some plain closed lakes have significant correlation with the dam distribution. Water levels of lakes having dams decrease dramatically, whereas open lakes without dams remain generally stable. This indicates that overexploitation of water resources in Central Asia has resulted in lake level decline.