A multi-tool, multi-method approach for improved qualitative and quantitative characterization of hydraulic groundwater relationships and resources

抽水井通常安装在识别良好的含水层中，含水层要么是粒状(由砂砾组成)，要么是裂隙岩石。假设从井中抽取的地下水来自安装井的含水层。然而，有一个特殊的情况尚未在文献中得到很好的记录，也没有得到彻底的调查：泵井安装在沉积物或裂隙岩石中，但在这两种情况下，都靠近这两种含水层之间的界面。在颗粒层通常覆盖在破碎的基岩上的区域地质框架内，抽水井可能恰好安装在矿床的下部恰好在基岩上方，或在基岩的上部，恰好在矿床的下方。在这两种配置中，人们可能会怀疑抽水井产生的水可能由两种不同的地下水组成：一种来自沉积物，另一种来自基岩。如果这两类含水层之间存在水力连接，就会出现这种情况。这样的连接可能是自然预先存在的，在那里破碎岩石的不连续面自然会与矿床相交。或者，如果通过岩石的钻探作业在含水层之间建立了水力连接(沿着套管底部的优先通道，穿透破裂岩石的上部)，则可能是人为诱导的。在这两种配置中，抽水井可以被称为“混合井”，因为它们收集来自颗粒含水层和裂隙岩石含水层的水。这项拟议研究的目的是建立一种方法，以便能够描述这两类含水层之间的水力联系。这一特征将使我们能够量化靠近水井的两类含水层之间以及在当地和区域范围内的地下水交换情况，并有助于了解水井供应的地下水的来源。在适当管理地下水资源时，这些方面至关重要。将获得更多关于可能污染的来源的知识。这项拟议的研究还将导致建立新的工具，以评估含水层的脆弱性并确保更好地保护资源。拟议的进行这项研究的方法本质上是全面的，并结合了以下几个方面：建立所调查问题的理论基础、进行现场试验、建模和数值试验。

Pumping wells are usually installed in a well-identified aquifer, either granular (composed of sand and gravel) or fractured rock. It is assumed that the groundwater extracted from the well comes from the aquifer in which the well is installed. However, there is a particular case which has not yet been well documented in the literature, nor thoroughly investigated so far: that of pumping wells which are installed either in deposit or in fractured rock, but in both instances, close to the interface between these two types of aquifers. Within a regional geological framework where granular layers usually overlay the fractured bedrock, pumping wells may happen to be installed either in the lower part of the deposit just above the bedrock, or in the upper part of the bedrock, just below the deposit. In both of these configurations, one may suspect that the water produced by the pumping well could be composed of a mix of two different groundwaters: one coming from the deposit and the other coming from the bedrock. This situation would arise if hydraulic connections exist between the two types of aquifers. Such connections may be naturally preexisting, where discontinuities of the fractured rock would naturally intersect with the deposit. Or they may be artificially induced, in the case where drilling operations through the rock have created a hydraulic connection between the aquifers (preferential pathways along the bottom part of the casing, penetrating the upper part of the fractured rock). In both configurations, the pumping wells could be qualified as "mixt wells" because they collect waters originating from both the granular aquifer and the fractured-rock aquifer. The aim of this proposed research is to set up a methodology allowing to characterize the hydraulic connections between the two types of aquifers. This characterization would allow us to quantify the groundwater exchanges between the two types of aquifers close to the wells and at local and regional scales, and to help to understand the origin of groundwater supplied by wells. These aspects are of crucial importance when appropriately managing groundwater resources. More knowledge will be gained about origins of possible contaminations. This proposed research will also lead to the establishment of new tools for assessing the vulnerability of aquifers and ensuring a better protection of the resource. The proposed approach to perform this research is holistic in nature and combines the following: establishing the theoretical bases of the investigated issue, performing in situ field tests, modeling and numerical tests.