Studio dei processi di ricarica naturale di corpi idrici sotterranei attraverso l'analisi di serie temporali

Nella Regione Emilia-Romagna, la zona delle conoidi ha una valenza strategica essendo la principale fonte di approvvigionamento idropotabile per le utenze civili, oltre che sostegno per le attività industriali ed agricole. All’interno di questo contesto ci si è soffermati sulla provincia di Piacenza, scegliendo come aree di studio le Conoidi del Trebbia e dell’Arda, per valutare le dinamiche di ricarica naturale attraverso l’identificazione della relazione che intercorre fra (i) l’entità dei deflussi superficiali riferiti ai corsi idrici che alimentano le conoidi, e (ii) il livello piezometrico nei rispettivi acquiferi. L’analisi è stata condotta applicando il modello Auto-Regressive Distributed Lag (ARDL)

Sustainable groundwater management based on probabilistic risk analysis

Risk assessment related to the qualitative/quantitative status of groundwater is a controversial issue, compared to which it is difficult to identify an exhaustive approach. A key factor for assessing vulnerability of aquifers is the analysis of natural renewal capacity associated with the quantity of available resource and compared to the overall water demand. Groundwater recharge is a complex process to analyze because it varies in space and time, and may be severely affected by future scenarios related to climate change and population dynamics. At the same time, local and diffuse contaminations may threaten the quality of groundwater availability with respect to the standards provided to the different uses and represent a critical environmental issue. Consequently, even if there are many studies dealing with groundwater vulnerability, the definition of a shared approach capable of (i) exhaustively describing in an integrated framework the phenomena occurring in different hydrogeological and climatic contexts and (ii) considering all the significant uncertainties according to a stochastic method, has not yet been achieved. In order to address these points, this thesis suggest an innovative methodological framework in which application of uncertainty quantification is applied both to parametric uncertainty, which is relevant to subsurface flow and transport processes, and to the projections of climate change scenarios. In support of this, an algorithm is applied and further developed based on metamodeling techniques to accelerate risk and global sensitivity analysis. The algorithm is applied to different case studies in order to provide an insight on some of the main quantitative/qualitative processes that affect groundwater status, leading to potentially risk conditions. The results presented in this work lay the basis for the computation of indicators which can be used for the assessment of the vulnerability of groundwater at different scales, in accordance with the requirements of European and National Regulations

Dinamiche di ricarica nella conoide del Trebbia

ANALIZZARE LE SERIE TEMPORALI DEI LIVELLI PIEZOMETRICI DELLE ACQUE SOTTERRANEE E DEI LIVELLI DEI CORSI D’ACQUA PERMETTE DI OTTENERE INDICAZIONI PRELIMINARI IN MERITO ALLE DINAMICHE DI RICARICA NATURALE DEI CORPI IDRICI SOTTERRANEI IN PARTICOLARI CONTESTI TERRITORIALI. LO STUDIO SULLA CONOIDE DEL TREBBIA NEL PIACENTINO

Surface water-groundwater interaction and nitrate persistence in unconfined high-conductivity aquifers investigated via time series analysis

Groundwater monitoring and protection are crucial issues within the environmental policies of the European Union. European directives require to (i) identify and characterize groundwater bodies, and (ii) reach specific quantitative/qualitative standards for each identified aquifer. The Italian laws incorporate these indications and provide technical criteria to characterize groundwater bodies. In this context, strategies aimed at preventing groundwater depletion play a relevant role in the conservation of water resources. In this study, we focus on the analysis of the underlying mechanisms of natural recharge for an unconfined high-conductivity aquifer. In particular, we refer to the area of the Apennines alluvial fan of the Emilia-Romagna Region. The portion of the cones close to the Apennines consists in high-permeable deposits that extend up to several hundred meters underground. A monolayer phreatic aquifer, connected directly to the surface, is located in this area. Widespread water withdrawals are present for agricultural and industrial purposes. For this reason, the analysis of nitrate concentration in groundwater represents a crucial issue. The use of nitrogen fertilizers and spreading of sewage and sludge in the soil are considered the main sources of nitric pollution. Based on time series analysis, we investigate the natural recharge dynamics by observing the influence of hydrometric variations on the piezometry, and the relationship between water level and nitrate concentration in the aquifer. We do this by means of autoregressive moving average models. The basic idea is to represent hydrological time series as single realizations of stochastic processes. In this context, we provide a basis to estimate groundwater vulnerability through an insight on surface water-groundwater interaction, and the persistence associated with nitrate concentration in an unconfined high-conductivity aquifer

Metabolic Modelling: A Strategic Planning Tool for Water Supply Systems Management

Water resources are essential for the economic development and sustenance of human activities belonging to the civil, agricultural and industrial sectors. Increasing water stress conditions, mainly due to climate change and population growth, imply the need to improve the resilience of water supply systems and account for sustainability of water withdrawals. Metabolic modelling approaches represent a flexible tool able to provide a support to decision making in the medium-long term, based on sustainability criteria. Here, these concepts are adopted to analyse part of the water supply network in the Province of Reggio-Emilia (Italy). Different water withdrawals scenarios are considered to account for a potential decrease in water resources availability from a quantitative perspective. As a second step, these scenarios are compared by means of a set of key performance metrics able to identify the most sustainable long-term strategy for a dynamic management of the water supply system. Results of these analysis allow to increase the resilience of the network under future scenarios, while protecting the water resources

Coupled Effects of non-Newtonian Rheology and Aperture Variability on Flow in a Single Fracture

Modeling of non-Newtonian flow in fractured media is essential in hydraulic fracturing and drilling operations, EOR, environmental remediation, and to understand magma intrusions. An important step in the modeling effort is a detailed understanding of flow in a single fracture, as the fracture aperture is spatially variable. A large bibliography exists on Newtonian and non-Newtonian flow in variable aperture fractures. Ultimately, stochastic or deterministic modeling leads to the flowrate under a given pressure gradient as a function of the parameters describing the aperture variability and the fluid rheology. Typically, analytical or numerical studies are performed adopting a power-law (Oswald-de Waele) model. Yet the power-law model, routinely used e.g. for hydro-fracturing modeling, does not characterize real fluids at low and high shear rates. A more appropriate rheological model is provided by e.g. the four-parameter Carreau constitutive equation, which is in turn approximated by the more tractable truncated power-law model. Moreover, fluids of interest may exhibit yield stress, which requires the Bingham or Herschel-Bulkely model. This study employs different rheological models in the context of flow in variable aperture fractures, with the aim of understanding the coupled effect of rheology and aperture spatial variability with a simplified model. The aperture variation, modeled within a stochastic or deterministic framework, is taken to be one-dimensional and i) perpendicular; ii) parallel to the flow direction; for stochastic modeling, the influence of different distribution functions is examined. Results for the different rheological models are compared with those obtained for the pure power-law. The adoption of the latter model leads to overestimation of the flowrate, more so for large aperture variability. The presence of yield stress also induces significant changes in the resulting flowrate for assigned external pressure gradient