汇流阈值对提取叶尔羌河上游流域面积高程积分的影响

不同地貌单元,其汇流阈值的界定差异较大,而不同的汇流阈值直接影响河流长度、河网密度以及集水区面积的提取结果,因此,汇流阈值的界定是提取流域面积高程积分的关键.以叶尔羌河上游流域为研究对象,基于不同分辨率数字高程模型数据对叶尔羌河上游流域面积高程积分的提取结果,确定适宜分辨率的数字高程模型数据,探讨不同汇流阈值对叶尔羌河上游流域面积高程积分的影响.结果显示:(1)所选不同分辨率高程(DEM)数据提取的叶尔羌河上游流域面积高程积分的参数和空间分布特征变化较小,面积高程积分对数字高程数据的分辨率依赖性不强.(2)整体上,叶尔羌河上游流域面积高程积分最大值随汇流阈值的增大呈阶段性减小趋势,最小值呈阶段性增加趋势,均值呈波动状态,但逐渐趋于稳定.当汇流阈值为27000时,面积高程积分均值、最大值和最小值均趋于稳定,其可能是提取叶尔羌河上游流域面积高程积分的稳定阈值.

Influence of confluence threshold on extracting hypsometric integral of Upper Yarkant Basin

Background, aim, and scope There are different threshold values of confluence of different geomorphic, and threshold value of confluence is the key to extract hypsometric integral (HI) of a watershed. This paper is to determine the DEM with suitable resolution, and analyze the influence of different threshold values of confluence on the results of extracting HI of the Upper Yarkant Basin (UYB), so as to determine the stable threshold value of confluence for extracting HI of UYB. Materials and methods The DEM data of 30 m×30 m in the Upper Yarkant Basin is resampled according to different resolutions used the resampling tool of grid toolbox in ArcGIS 10.2 software. Then, the DEM data are processed with the hydrological analysis tool of ArcGIS 10.2 software, and the river network and HI are extracted. Results The number, total length and density of ravine decrease in a negative exponential, with the decrease of DEM resolution in the UYB, and the change trend is similar. The parameters and spatial distribution characteristics of HI in the UYB extracted from DEM data with different resolutions have little change. Discussion The results show that the max HI in the UYB decreases, and the min HI increases in stages with the increase of threshold value of confluence, and the difference between max HI and min HI decreases gradually; although mean HI is fluctuating, it tends to be stable gradually with the increase of threshold value of confluence, and its variance tends to be stable and close to 0.1, and HI is more suitable when threshold a value of confluence is 27000. Conclusions HI do not depend strongly on experimented DEM resolution, and the mean HI, max HI, min HI tend to be stable when the concentration threshold is 27000, which is the stable value of confluence of the extracted HI of the UYB. Recommendations and perspectives This study analyzed the impact of threshold value of confluence on extracting HI in UYB, and determined the stable threshold, which laid a foundation for the later study of the relationship between geomorphology and tectonic, lithology and climate in UYB.