基于遥感影像记录的新疆玛纳斯河下游冲积平原河道演变过程研究

Evolution of the Lower Reaches of the Manas River Based on Information from Remote Sensing Images

干旱区河流变迁与绿洲演变和沙漠进退密切相关,是近年来干旱区环境变化研究的焦点之一。玛纳斯河贯穿山地—绿洲—荒漠系统,是新疆准噶尔盆地环境演变的典型区域。文章利用遥感影像,结合实地测量的地貌与沉积记录、室内沉积分析和测年等资料,研究了玛纳斯河下游冲积平原河道演变过程,即近4 000多年来玛斯河在下游冲积平原发生了3次可识别的迁移事件及方向,河道变迁在空间上总体表现为一个自西南向东北迁移的过程。在此基础上,进一步讨论了玛纳斯河下游冲积平原河道的变迁原因及发展趋势,指出区域构造活动是影响玛纳斯河下游河道近4 000年来定向迁移的主要原因,并预测在没有异常气候波动和构造活动的影响下,今后一段时间内玛纳斯河不会发生大规模的迁移。

River change is closely related to oasis and desert evolvement, and therefore has been one of the focuses in the study of environmental change in arid regions in recent years. The Manas river runs through mountain, oasis and desert systems and is the largest river in the Junggar basin. Previously, many studies about the Manas river focused on changes in the runoff, but the evolution of its watercourse was neglected. This paper investigates the evolution of the lower reaches of the Manas river using interpretation of remote sensing images, field measurements and deposition analyses. The results showed that three migratory occurrences and directions could be identified in the lower reaches of the Manas river during the past 4 000 years. The lower reaches of the Manas river ran along the watercourse R1 4 000 years ago, migrated 6 km south to Xinzhuangzi and ran along watercourse R2 4 000-1 500 years ago, then changed its route again near Taipingqu and created the watercourse R3 1 500-500 years ago. The last migration of the Manas river occurred in the 16th century when the Manas river left its western watercourse and moved towards the north, near the Jiahezi reservoir, and flowed along the south side of the desert creating the watercourse R4 which is the current watercourse. As a whole, the spatial evolution of the lower reaches of the Manas river has experienced a migration from south-west to north-east. With this knowledge, this paper concludes that geology and tectonic movement are the main factors which have affected watercourse evolution, but the roles of climate and riversideg composition are not neglected. Finally, this paper forecasts that the Manas river will not move on a large scale in the future without preternatural tectonic movement and climate change.