1962—2019年锡尔河-咸海三角洲湿地时空变化及驱动因素

Spatio-temporal changes and driving factors of wetlands in the delta of the Syr Darya River-Aral Sea during 1962—2019

咸海周边环境变化对中亚干旱区生态稳定有重要影响,研究锡尔河-咸海三角洲湿地演变对认识流域生态环境变化、实施生态修复等具有重要意义。基于多源遥感数据采用面向对象分层提取法方法,分析1962—2019年锡尔河下游三角洲湿地的时空变化特征,并结合咸海变化、耕地变化、河流水量和水利工程建设等探讨近60a湿地变化的驱动因素。研究表明:①近60 a在咸海持续萎缩的情况下,锡尔河下游三角洲湿地呈现先减小后增加的变化趋势,其中1962—1980年、1981—1991年和1992—2019年3个阶段的变化率分别为-38.29 km 2/a、193.35 km 2/a和14.36 km 2/a;②湿地变化有明显的空间差异,锡尔河南、北2个入湖口区的湿地自1980年以来向咸海湖区扩张明显,耕地混合区的湿地自1991年以来向河道两侧扩张;③1962年后在入三角洲径流量总体减少的趋势下,灌渠建设和生态用水配置是三角洲湿地面积增加的主要原因,间接导致咸海入湖水量减少,咸海快速萎缩。锡尔河三角洲湿地恢复与咸海干涸形成了明显的生态反差,不利于咸海周边生态的整体恢复。

The changing environment around the Aral Sea has a great impact on the ecological stability of the arid area in Central Asia,to this end,the study on the wetland evolution of the Syr Darya-Aral Sea delta is of great significance to gain further insight in the changing valley and find out the solution for ecological recovery.Based on the multi-source remote sensing data,this paper extracted the wetland information from images by an object-oriented hierarchical extraction method,and analyzed temporal and spatial variations in the delta wetland of the lower of the Syr Darya River from1962 to 2019.Also,this paper took such elements as the changes of the Aral Sea and the farmlands,river discharges,the water conservancy projects and others into consideration and discussed the drivers of the near 60 a wetland changes.This study shows that as the constant shrink of the Aral Sea,the landmass of delta wetland of the lower of the Syr Darya River decreased first,then it grew bigger.During this period,the rate of change presents-38.29 km 2/a,193.35 km 2/a and 14.36 km 2/a in 3 phases:1962—1980,1981—1991 and 1992—2019 respectively.The wetland change has a distinctive spatial variation.Since 1980,two wetlands laying near the northern and the south estuaries of the Syr Darya River have largely expanded towards the Aral Sea.The area between the wetlands and the farmlands has extended to two sides of the river since 1991.Given the fact of the reduced runoff entering the delta after 1962,the irrigation network project and the ecological water allocation play the main role in growing the delta wetland.On the other hand,these projects indirectly cut down the flow entering the Aral Sea,which leads to the rapid shrink of the Aral Sea.The delta wetland recovery poses a striking contrast with the degradation of the Aral Sea.In this case,the ecological environment around the Aral Sea will undergo an inferior recovery.