Contrasting Patterns in the Decrease of Spatial Variability With Increasing Catchment Area Between Stream Discharge and Water Chemistry
Contrasting Patterns in the Decrease of Spatial Variability With Increasing Catchment Area Between Stream Discharge and Water Chemistry
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DOI：
10.1029/2018wr024302
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发表时间：
2019-08
影响因子：
5.4
通讯作者：
T. Egusa;T. Kumagai;T. Oda;T. Gomi;N. Ohte
中科院分区：
文献类型：
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作者：
T. Egusa;T. Kumagai;T. Oda;T. Gomi;N. Ohte
了解河流流量和水化学的空间变异性如何随着集水面积的增加而减少，是提高我们预测无资料流域水文和地球化学过程的能力所必需的。我们调查了这种减少的差异，随着流域之间的集水面积和比流量（Qs）和水化学参数。我们将变异性随汇水面积增加而减小的斜率定义为标准差和变异系数（分别为δSD和δCV）的减小率，对于随机变量的简单混合（随机混合），两者均为-0.5。所有Qs的δSD和δCV值均小于-0.5，而大多数水化学值的δSD和δCV值均大于-0.5，表明随着集水面积的增加，Qs的空间变异性比随机混合下降得更陡，而水化学的空间变异性下降得不那么陡。δSD和δCV与空间不相似性指数以及参数均值随流域面积的相对变化均呈线性关系。结果表明，Qs和水化学的δSD或δCV的差异可以用不同的空间结构来解释，不同的Qs值和相似的水化学值在空间上分别位于一起。根据Qs和水化学，δSD和δCV的差异应显著影响代表性基本面积的确定，因此在根据低阶河流的空间变异性预测代表性基本面积时需要考虑。
Understanding how spatial variability in stream discharge and water chemistry decrease with increasing catchment area is required to improve our ability to predict hydrological and biogeochemical processes in ungauged basins. We investigated differences in this decrease of variability with increasing catchment area among catchments and among specific discharge (Qs) and water chemistry parameters. We defined the slope of the decrease in the variability with increasing catchment area as the rate of decrease in the standard deviation and coefficient of variation (δSD and δCV, respectively), both of which are −0.5 for the simple mixing of random variables (random mixing). All δSD and δCV values of Qs were less than −0.5, while those of most water chemistry values were greater than −0.5, indicating that with increased catchment area the spatial variability of Qs decreased more steeply than for random mixing, while for water chemistry they decreased less steeply. δSD and δCV had linear relationships with both the spatial dissimilarity index and relative changes in parameters' mean values with increasing catchment area. It suggested that differences in δSD or δCV for Qs and water chemistry can be explained by the different spatial structures, where dissimilar values of Qs and similar values of water chemistry, respectively, are located close together in space. Differences in δSD and δCV according to Qs and water chemistry should significantly affect the determination of representative elementary area and therefore need to be considered when predicting representative elementary area from spatial variability of low‐order streams.