ABSTRACT

Quantification of the isotope altitude effect from precipitation allows the identification of recharge altitudes in high-relief areas. However, steep terrains frequently limit the use of this precipitation-based approach. Perennial rivers often provide easy, year-round access for water sampling. However, in high-relief regions rivers may not adequately represent regional precipitation isotope patterns because they integrate isotope signals along their course. This prevents the calculation of an altitudinal isotope gradient from river water samples alone. We present a study that shows how a river-based sampling approach served to determine the altitude effect. Replacing the original sample site altitude with the mean upstream catchment elevation as calculated from a digital elevation model allowed us to establish a plausible altitude isotope effect from stream water. The correction approach was verified independently using precipitation isotope data. This approach can potentially be transferred to other regions where precipitation sampling at various elevations is difficult to determine.

摘要

对降水的同位素高度效应进行量化可以确定高地貌地区的补给高度。然而，陡峭的地形经常限制这种基于降水的方法的使用。常年河流通常提供方便的全年水采样通道。然而，在高地势地区，河流可能无法充分代表区域降水同位素模式，因为它们沿其流向整合了同位素信号。这阻止了仅从河水样本计算海拔同位素梯度。我们提出了一项研究，展示了基于河流的采样方法如何用于确定海拔效应。用从数字高程模型计算的平均上游流域高程替换原始样本点海拔高度，使我们能够从溪水中建立合理的海拔同位素效应。使用降水同位素数据独立验证了校正方法。这种方法可能会转移到其他地区，在这些地区很难确定不同海拔的降水采样。