Separating physical and meteorological controls of variable transit times in zero‐order catchments
Separating physical and meteorological controls of variable transit times in zero‐order catchments
复制标题
零级流域中可变传输时间的物理和气象分离控制
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
S. Lyon
中科院分区：
文献类型：
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作者：
Ingo Heidbüchel;P. Troch;S. Lyon
我们观测了北美季风季6个零级嵌套小流域次表层的水通量和同位素组成，发现平均渡越时间(MTT)随季节而变化，每年都会出现不同的MTT空间格局。对于每个季风季，可以将MTT与不同的物理集水区属性相关联。2007年，MTT与平均土壤深度的相关性最好，2008年土壤导水率在解释变异性方面变得重要起来，2009年平面曲率的相关性最好。三个季风季气象强迫的差异解释了MTT的时间变化。2007年，一系列降水事件导致一些零级集水区的土壤蓄水能力被超过。结果，这些集水区开始产生快速径流(陆上径流和大孔隙径流)。2008年，降水事件在整个季节的分布更加均匀，土壤没有饱和，径流系数下降，因为更多的水通过蒸发蒸腾离开集水区，而且由于基质流占主导地位，土壤的水力传导性变得更强的控制。2009年的季风异常干燥，土壤储存变得枯竭，水主要通过基岩通道流动。因此，地形参数在决定水到达集水口的速度方面变得重要起来。为了更好地理解是什么控制了MTT，我们提出了一个无量纲数字，它有助于确定分区阈值，并将降水事件分类为在我们的零级集水区观察到的三种响应模式之一。
We observed water fluxes and isotopic compositions within the subsurface of six small nested zero‐order catchments over the course of three North American monsoon seasons and found that mean transit times (mTTs) were variable between seasons and different spatial patterns of mTTs emerged each year. For each monsoon season, it was possible to correlate mTTs with a different physical catchment property. In 2007, mTTs correlated best with mean soil depth, in 2008 soil hydraulic conductivity gained importance in explaining the variability and in 2009 planform curvature showed the best correlation. Differences in meteorological forcing between the three monsoon seasons explained the temporal variability of mTTs. In 2007, a series of precipitation events caused the storage capacity of the soils of some of the zero‐order catchments to be exceeded. As a result those catchments started producing quick runoff (overland and macropore flow). In 2008, precipitation events were more evenly distributed throughout the season, soils did not saturate, runoff coefficients decreased because more water left the catchment via evapotranspiration and soil hydraulic conductivity became a stronger control since matrix flow dominated. The 2009 monsoon was unusually dry, the soil storage became depleted and water flowed mainly through bedrock pathways. Therefore, topographic parameters gained importance in determining how quickly water arrived at the catchment outlet. In order to improve our understanding of what controls mTTs we suggest a dimensionless number that helps identifying partitioning thresholds and sorts precipitation events into one of the three response modes that were observed in our zero‐order catchments.