Groundwater Circulation in Fractured and Karstic Aquifers of the Umbria-Marche Apennine

Abstract

The Umbria-Marche Apennine has a large number of springs that drain water stored in carbonate formations. Spring groundwater constitutes a crucial freshwater resource for many countries, regions, and cities around the world. This study aimed to understand the hydrological mechanisms behind groundwater circulation and their relationship to the structural and stratigraphic settings of specific aquifers. Recession analysis and time series analysis were applied to the daily discharge of six springs monitored over eight years. Both analyses indicated the presence of two types of aquifers: aquifer with unimodal behavior and aquifer with bimodal behavior. The first are characterized by two hydrodynamic sub-regimes, in which fracture networks control the baseflow and conduit networks control the quickflow. In contrast, other springs present only one hydrodynamic sub-regime related to fracture network drainage. Time series analysis confirms the results of recession analysis, showing a large memory effect and a large response time, implying the dominance of the baseflow sub-regime. These results indicate that the Maiolica Formation is characterized by a high degree of fracturation and slight karstification, which control infiltration and percolation, whereas the Calcare Massiccio Formation regulates groundwater circulation in the deeper zones of the aquifer, characterized by a high degree of karstification through moderately developed conduit networks.Water 2020, 12, 1039 2 of 21 linear baseflow recession. Kovács et al. [12] showed that the recession coefficient allows for obtaining important information about aquifer hydraulic parameters and conduit network characteristics. One main advantage of recession curve analysis is that a set of empirical, quantitative parameters attributed to drainage mechanisms can be calculated [15].Analysis of individual recession periods sometimes generates inconsistences related to the complexity of groundwater circulation and the processes acting on the system [16]. Therefore, a master recession curve (MRC) is commonly used for simultaneously analyzing a set of hydrograph recessions at a particular catchment [17][18][19][20][21][22].Malík and Vojtková [23] performed a recession curve analysis to evaluate the karstification degree and the hydrodynamic behavior of an aquifer. With given recession coefficients and initial discharge values, both runoff and partial runoff segments (sub-regimes) can be fully described. In karst hydrogeology, the term "sub-regime" refers to the changing conditions of a groundwater system, its characteristic behavior, or the controlling of natural processes, which usually occur in a regular pattern [24].Apart from recession analysis, univariate and bivariate analyses can also be performed on spring hydrographs. Valuable indirect information regarding karst systems can be obtained by performing a time series analysis [25]. Mangin [26] developed a specific methodology for studying the input-output relationships in karst aquifers, as well as for performing auto-correl...

A Holistic Approach to Study Groundwater-Surface Water Modifications Induced by Strong Earthquakes: The Case of Campiano Catchment (Central Italy)

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Study of Groundwater Flow Properties in a Karst System by Coupled Analysis of Diverse Environmental Tracers and Discharge Dynamics

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