This paper concerns a stepwise modelling procedure for groundwater flow simulation in a folded and faulted, multilayer carbonate aquifer, which constitutes a source of good quality water for human consumption in the Apennine Range in Central Italy. A perennial river acts as the main natural drain for groundwater while sustaining valuable water-related ecosystems. The spatial distribution of recharge was estimated using the Thornthwaite–Mather method on 60 years of climate data. The system was conceptualized as three main aquifers separated by two locally discontinuous aquitards. Three numerical models were implemented by gradually adding complexity to the model grid: single layer (2D), three layers (quasi-3D) and five layers (fully 3D), using an equivalent porous medium approach, in order to find the best solution with a parsimonious model setting. To overcome dry-cell problems in the fully 3D model, the Newton–Raphson formulation for MODFLOW-2005 was invoked. The calibration results show that a fully 3D model was required to match the observed distribution of aquifer outflow to the river baseflow. The numerical model demonstrated the major impact of folded and faulted geological structures on controlling the flow dynamics in terms of flow direction, water heads and the spatial distribution of the outflows to the river and springs.

中文翻译：

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识别控制折叠碳酸盐含水层系统中地下水流动的结构特征的逐步建模方法

本文涉及在折叠和断层的多层碳酸盐含水层中模拟地下水流动的逐步建模程序，该含水层构成了意大利中部亚平宁山脉供人类消费的优质水源。一条常年河流作为地下水的主要自然排水沟，同时维持着宝贵的与水有关的生态系统。使用 Thornthwaite-Mather 方法对 60 年的气候数据估计补给的空间分布。该系统被概念化为由两个局部不连续的隔水层隔开的三个主要含水层。通过逐渐增加模型网格的复杂性来实现三个数值模型：单层（2D）、三层（准 3D）和五层（全 3D），使用等效多孔介质方法，以找到最佳解决方案简约的模型设置。为了克服全 3D 模型中的干电池问题，调用了 MODFLOW-2005 的 Newton-Raphson 公式。校准结果表明，需要一个完整的 3D 模型才能将观测到的含水层流出量分布与河流基流相匹配。数值模型证明了褶皱和断层地质构造对控制流向、水头以及河流和泉水流出量的空间分布方面的流动动力学的主要影响。