Spatio‐temporal variability of the isotopic input signal in a partly forested catchment: Implications for hydrograph separation
Spatio‐temporal variability of the isotopic input signal in a partly forested catchment: Implications for hydrograph separation
复制标题
部分森林覆盖的流域中同位素输入信号的时空变化：对水文过程线分离的影响
作者：
C. Cayuela;J. Latron;J. Geris;P. Llorens
降水的同位素组成（D和18O）已被广泛用作水示踪研究的输入信号。鉴于最近的努力已经投入到开发方法，以提高我们对水文过程的理解和建模（例如，在这些研究中，由于降水的同位素组成的时空变异性（如渡时分布或年轻水分数），人们对降水同位素组成的时空变异性的关注较少。在这里，我们研究了由于降水的同位素组成的时空变异性而导致的基于同位素的过程线分离的不确定性。这项研究是在地中海源头流域（0.56平方公里）。在这个相对较小的集水区的三个地点收集了降雨和穿透降雨样本，并在出口处收集了溪流样本。结果表明，在整个事件中，输入信号的空间变异性比其时间变异性对过程线分离结果的影响更大。然而，由于时空变异性，基于同位素的过程线分离确定的事件前水的差异在事件之间不同，范围在1%和14%之间。根据流域尺度的等值线图，还可以确定最具代表性的采样位置。这项研究证实，即使在小的源头集水区，时空变化可能是显着的。因此，重要的是要描述这种变异性，并确定最佳的采样策略，以减少我们对流域水文过程的理解的不确定性。
The isotopic composition of precipitation (D and 18O) has been widely used as an input signal in water tracer studies. Whereas much recent effort has been put into developing methodologies to improve our understanding and modelling of hydrological processes (e.g., transit‐time distributions or young water fractions), less attention has been paid to the spatio‐temporal variability of the isotopic composition of precipitation, used as input signal in these studies. Here, we investigated the uncertainty in isotope‐based hydrograph separation due to the spatio‐temporal variability of the isotopic composition of precipitation. The study was carried out in a Mediterranean headwater catchment (0.56 km2). Rainfall and throughfall samples were collected at three locations across this relatively small catchment, and stream water samples were collected at the outlet. Results showed that throughout an event, the spatial variability of the input signal had a higher impact on hydrograph separation results than its temporal variability. However, differences in isotope‐based hydrograph separation determined preevent water due to the spatio‐temporal variability were different between events and ranged between 1 and 14%. Based on catchment‐scale isoscapes, the most representative sampling location could also be identified. This study confirms that even in small headwater catchments, spatio‐temporal variability can be significant. Therefore, it is important to characterize this variability and identify the best sampling strategy to reduce the uncertainty in our understanding of catchment hydrological processes.