长江源当曲流域河道时空演变特征研究

Spatiotemporal evolution characteristics of river channels of Dangqu River Basin in source region of Yangtze River

摘要

【目的】全球气候变暖背景下,长江源气温与降水均呈增加趋势,融冰融雪增多,河流演变加剧。明确高原河道在气候变化下的时空演变规律,对提升气候变化下高原河流的响应演变特征认知及维护生态环境意义重大。【方法】基于1990—2023年长江源当曲流域的遥感影像及附近三个气象站的气温、降水数据,采用MNDWI水体指数法、河道中心线法、Mann-Kendall趋势分析法和MVC最大值合成法,定量研究长江源当曲流域的河道时空演变特征,分析1990—2023年期间长江源河道弯曲度、河道宽度和河道横向迁移率的年际变化规律。【结果】结果显示:当曲流域152 km长的河段中,顺直河道占比约1/3,弯曲河道占比约2/3。在过去34 a中,当曲流域河道平均弯曲度为1.14,34 a间弯曲度仅减小2%。当曲河道河宽持续增大,河宽平均增幅9.4%,年均增加0.4 m/a。河道归一化横向迁移率[=总横向迁移距离/（迁移对应年份×河宽）]减少48%,34 a年均减少0.014。【结论】河道河宽与归一化横向迁移率受气温、降水影响显著,气温升高诱发的融冰融雪增加协同降水增多共同导致河道流量增大、水位上升,促使当曲流域河道增宽。同时,上述水文条件的改变有利于植被生长,植被固岸作用增强,抑制了河道横向迁移,归一化横向迁移率呈下降趋势。

Abstract

[Objective] In the context of global climate warming, both temperature and precipitation in the source region of the Yangtze River have shown increasing trends, leading to enhanced glacier melt and snowmelt and intensified river evolution. Clarifying the spatiotemporal evolution patterns of plateau river channels under climate change is of great significance for the enhanced understanding of response and evolutionary characteristics of plateau rivers and for the conservation of ecological environment. [Methods]Based on remote sensing imagery of the Dangqu River Basin in the source region of the Yangtze River and temperature and precipitation data from three nearby meteorological stations from 1990 to 2023, the spatiotemporal evolution patterns of river channels in the Dangqu River Basin were quantitatively investigated. This was achieved by the MNDWI method, channel centerline method, Mann-Kendall trend analysis, and maximum value composite(MVC) method. Additionally, interannual variations in curvature, width, and lateral migration rates of river channels from 1990 to 2023 were analyzed. [Results] The result showed that within the 152 km river section of the Dangqu River Basin, straight channels accounted for approximately one-third, while meandering channels accounted for two-thirds. Over the past 34 years, the average curvature of river channels in the Dangqu River Basin was 1. 14, exhibiting only a 2% decrease during this period. The river width of the Dangqu River continued to increase, with an average growth of 9. 4% and an annual increase of 0. 4 m/a. The normalized lateral migration rate of the river channels [= total lateral migration distance/m（year of migration × river width）]decreased by 48%, with an average annual reduction of 0. 014 over the 34-year period. [Conclusion] The river width and normalized lateral migration rate are significantly influenced by temperature and precipitation. Increased glacier melt and snowmelt induced by rising temperatures, combined with higher precipitation, jointly lead to higher river discharge and elevated water levels, thereby promoting the widening of river channels in the Dangqu River Basin. In addition, these changes in hydrological conditions are favorable for vegetation growth, which strengthens bank stabilization and suppresses lateral channel migration, resulting in a decreasing trend in the normalized lateral migration rate.

关键词

弯曲河流 / 河道演变 / 横向迁移 / 长江源 / 时空演变 / 当曲流域 / 遥感解译 / 气候变化

Key words

meandering river / river channel evolution / lateral migration / source region of Yangtze River / spatiotemporal evolution / Dangqu River Basin / remote sensing interpretation / climate change

基金资助

国家重点研发计划政府间国际科技创新合作重点专项(2022YFE0128200)

国家自然科学基金项目(52279072)

四川省科技计划资助(2025ZNSFSC0412)