考虑水力连通的羌塘内流区洼地单元提取与分类

Extraction and classification of endorheic units in the Qiangtang endorheic basin considering hydraulic connectivity

  • 摘要: 羌塘内流区是青藏高原面积最大的内流区, 气候变化正在加剧其湖泊水系结构与水量的演变, 开展内流区流域调查并科学估算其水资源的变化具有重要意义。本文提出一种新型内流区流域划分方法, 该方法通过引入高程-面积联合阈值, 以解决由气候变化与数字高程模型分辨率等因素引起的洼地单元提取难题。基于已监测的羌塘内流区流域重组与湖泊水位的变动幅度, 确定了高程-面积联合阈值分别为10 m和50 km2, 并对洼地单元进行划分, 共识别出163个具有合理集水面积、永久性分水岭的封闭内流区洼地单元。引入多个相关数据集及已有算法评估本方法, 结果表明: 该方法适用于大尺度内流区洼地单元提取, 提取精度优于现有算法及数据产品; 依据洼地单元间水力连通特征, 将全区163个洼地单元划分为5种主要类型, 其中以"上下游互通型"(Ⅱ型)、"高山型"(Ⅳ型)洼地单元为主, "凹陷型"(Ⅴ型)洼地单元则多与其他类型复合存在, 受气候条件的影响更加显著。

     

    Abstract: The Qiangtang endorheic basin, the largest endorheic basin in the Tibetan Plateau, is experiencing a rapid evolution of its lake system structure and water quantity owing to climate change. Considering the impacts of climate change on the boundaries of endorheic units, we propose a novel delineation algorithm introducing the Joint Elevation-Area Threshold (JEAT) to address delineation issues caused by climate change. Firstly, by observing the reorganizations and fluctuations in lake levels in the Qiangtang endorheic zone, we determined that the JEAT was 10 m and 50 km2, respectively. Next, a total of 163 endorheic units with reasonable contribution area and permanent boundaries were identified. The results demonstrated that the algorithm is suitable for extracting endorheic units on a large scale, and the extraction accuracy is superior to that of other existing algorithms and datasets. Subsequently, 163 endorheic units were categorized into five main types based on weak watershed type, with the upstream-downstream connected type (Type Ⅱ) and alpine type (Type Ⅳ) being the main ones. Pit type (Type Ⅴ) watersheds tended to mostly coexist with other types, exhibiting a more intense response to the connectivity characteristics of large depressions at different periods.

     

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