A hydrogeophysical field experiment was conducted on a karst hydrosystem in the south of France to investigate groundwater transfer and storage variability at a scale of a few hundred meters. A 200-m-long N/S tunnel going through limestone provided the unique opportunity to set up measurements with original configurations inside the unsaturated zone. Three geophysical methods were used: gravimetry, electrical, and seismic. Two-dimensional electrical resistivity and seismic velocity images were retrieved by surrounding the medium with electrodes and geophones, both at the surface and inside the tunnel to improve the sensitivity in depth. This gave information about the weathering state but also about the limestone content and associated porosity characteristics, as the methods are sensitive to distinct properties with different resolution patterns. A time-lapse gravity surface-to-tunnel profile supplied information on the seasonal water mass changes and its variations along the tunnel. Besides, tracers were injected on each side of the profile from the surface and the restitution was sampled in the tunnel drip flows. A contrasting hydrological behavior was evidenced on each side of the tunnel from temporal gravity measurements and tracing tests. The analysis of the whole dataset allowed for better interpretation of the imaged structures, with different hydrological functioning. This study demonstrates the variability of the karst behavior at the scale of a few hundred meters and the benefits of a multi-method approach coupling hydrological and geophysical measurements. This kind of experiment provides fundamental understanding of systems that cannot be directly observed.

在法国南部的岩溶水系统上进行了水文地球物理现场实验，以研究数百米尺度的地下水转移和储存变化。一条穿过石灰岩的 200 米长 N/S 隧道提供了独特的机会，可以在非饱和带内使用原始配置进行测量。使用了三种地球物理方法：重力法、电法和地震法。通过在地表和隧道内部用电极和地震检波器包围介质来获取二维电阻率和地震速度图像，以提高深度的灵敏度。这提供了有关风化状态的信息，但也提供了有关石灰石含量和相关孔隙度特征的信息，因为这些方法对具有不同分辨率模式的不同属性很敏感。延时重力表面到隧道剖面提供了有关季节性水体变化及其沿隧道变化的信息。此外，示踪剂从表面注入剖面的每一侧，并在隧道滴流中采样恢复。从时间重力测量和追踪测试中，隧道的每一侧都显示出对比鲜明的水文行为。对整个数据集的分析可以更好地解释具有不同水文功能的成像结构。这项研究证明了几百米尺度的岩溶行为的可变性，以及结合水文和地球物理测量的多方法方法的好处。这种实验提供了对无法直接观察到的系统的基本理解。