Identifying the hydrological behavior of a complex karst system using stable isotopes
Identifying the hydrological behavior of a complex karst system using stable isotopes
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DOI：
10.1016/j.jhydrol.2019.123956
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发表时间：
2019-10-01
影响因子：
6.4
通讯作者：
Bezak, Nejc
中科院分区：
文献类型：
--
作者：
Rusjan, Simon;Sapac, Klaudija;Bezak, Nejc
喀斯特系统具有高度的水文非均质性，主要与高度可变的渗透率有关，在小空间尺度上变化显著。这使得追踪和量化水流路径成为一项极其苛刻的任务。在这项研究中，我们提出了一个复杂的喀斯特系统的水文特征分析，卢布尔雅尼卡河流域在斯洛文尼亚中部。得到了降水作为输入、岩溶泉/汇作为输出的稳定同位素组成（δ O-18、δ H-2）的空间分布数据。这些数据用于识别空间和季节模式以及喀斯特系统在不同水文条件下的水文行为。卢布尔雅尼察河流域大陆气团和地中海气团的强烈混合使降水源识别变得困难。然而，降水同位素组成分析结果表明，在岩溶泉和岩溶汇的δ O-18、δ H-2值中也可以识别出一种空间格局。沿主导岩溶通道，三角洲O-18值、三角洲H-2值的空间差异减小。以δ O-18和δ H-2示踪剂估算的平均运移时间（MTT）相似，主要岩溶管道和支流的平均运移时间在0.34 ~ 0.74年之间。对于没有广泛的深层地下水储存的喀斯特集水区来说，这样一个相对较短的MIT是可以预期的。整个流域的年轻水比例（F-yw）为0.28，这意味着超过四分之一的总流量小于约2.3个月（假设流域运输时间用指数分布描述）。在岩溶集水区的不同地区，MTT的微小差异可能表明沿地下管道的水的强烈混合和均质化。然而，流域的均质化在很大程度上取决于先前的水文条件；在低流量条件下可以识别出同位素组成的差异，这可能表明岩溶泉的局部补给占主导地位。
Karst systems can be generally characterised by their high hydrological heterogeneities related mainly to highly variable permeabilities, which can significantly change over small spatial scales. This makes tracing and quantification of water flow pathways an extremely demanding task. In this study we present an analysis of hydrological characteristics of a complex karst system, the Ljubljanica river catchment in central Slovenia. Spatially distributed data on stable isotope composition (delta O-18, delta H-2) of precipitation as inputs, and of several karst springs/sinks as outputs, were obtained. These data were used to identify spatial and seasonal patterns and hydrological behaviour of the karst system in contrasting hydrological conditions. The intensive mixing of continental and Mediterranean air masses over the Ljubljanica river catchment makes the precipitation source identification difficult. However, the results of the precipitation isotopic composition analysis indicate a spatial pattern that could be recognised also in the delta O-18, delta H-2 values of the karst springs and sinks. Along the prevailing karst conduits, the spatial differences in the delta O-18, delta H-2 values decreased. The mean transit time (MTT) estimates using delta O-18, delta H-2 as tracers were similar, with those for the main karst conduits and tributaries ranging between 0.34 and 0.74 years. Such a relatively short MIT could be expected for karst catchments without extensive deep groundwater storage. The fraction of young water (F-yw) for the whole catchment was 0.28, meaning that more than one-quarter of the total discharge was younger than approximately 2.3 months (assuming that the catchment transit time is described by exponential distribution). Small differences in the MTT over different parts of the karst catchment area might indicate intensive mixing and homogenisation of water along the underground conduits. However, the catchment's homogenisation strongly depends on the preceding hydrological conditions; the differences in the isotope composition can be identified during low-flow conditions, which might indicate the dominant influence of the local recharge of the karst springs.