Giovanna De Filippis

The geothermal potential of the underground of the Salento peninsula (southern Italy)

The low-enthalpy geothermal energy systems exploit the underground as a heat reservoir, by coupling it with highly efficient heat pumps: in winter, the energy stored in the subsoil can be transferred to the surface to heat buildings, whereas in summer the surplus heat in buildings can be transferred back to the ground providing a cooling action. Despite the high costs for installation, low-enthalpy geothermal systems have high energy efficiency and, therefore, contribute to energy saving, to the use of renewable energy sources, to environmental sustainability (the effects on the hydrogeological cycle are often negligible) and to the reduction in fuel consumption and in gas emissions. In this paper, a simple methodology is proposed to assess the geothermal potential of the underground of the Salento peninsula (southern Italy) at the regional scale, by calculating the equivalent thermal performance of the subsoil, which expresses the thermal power that is potentially extractable and useful to heat or cool a building. Since the possibility of exploiting the underground as a heat reservoir depends on the physical properties and water saturation of rocks, previous detailed studies on the hydrostratigraphic setup of the region are the basis for this analysis of geothermal potential. The equivalent thermal performance depends on the thermal efficiencies of different lithological units, whose ranges of values, for heating only, are provided in literature. For this case study, a stochastic approach has been applied: several combinations of thermal efficiencies were randomly selected from the intervals of reference values for every hydrostratigraphic formation and the corresponding minimum depths below the ground surface that must be reached to get the desired equivalent thermal performance are computed. The results show that the underground of the Salento peninsula has great potentialities for heating of buildings, except for some coastal areas because the saltwater intrusion phenomenon could cause problems for the realization of low-enthalpy geothermal energy systems.

Modeling Groundwater Flow in Heterogeneous Porous Media with YAGMod

Modeling flow and transport in porous media requires the management of complexities related both to physical processes and to subsurface heterogeneity. A thorough approach needs a great number of spatially-distributed phenomenological parameters, which are seldom measured in the field. For instance, modeling a phreatic aquifer under high water extraction rates is very challenging, because it requires the simulation of variably-saturated flow. 3D steady groundwater flow is modeled with YAGMod (yet another groundwater flow model), a model based on a finite-difference conservative scheme and implemented in a computer code developed in Fortran90. YAGMod simulates also the presence of partially-saturated or dry cells. The proposed algorithm and other alternative methods developed to manage dry cells in the case of depleted aquifers are analyzed and compared to a simple test. Different approaches yield different solutions, among which, it is not possible to select the best one on the basis of physical arguments. A possible advantage of YAGMod is that no additional non-physical parameter is needed to overcome the numerical difficulties arising to handle drained cells. YAGMod also includes a module that allows one to identify the conductivity field for a phreatic aquifer by solving an inverse problem with the comparison model method.

Software tools for sustainable water resources management: the GIS-integrated FREEWAT platform

This paper aims at presenting the open source and public domain FREEWAT platform capabilities for water resource management, including: (i) pre-processing modules to facilitate the preparation of input data, (ii) modelling tools for the analysis of several processes aimed at supporting water resource management, and (iii) post-processing tools to present results.The FREEWAT platform is based on open source solutions to perform an integrated coupling between the QGIS desktop software, surface and subsurface model engines, mostly based on fully distributed and numerically-based codes developed by the USGS, and other software applications, and the SpatiaLite spatial database. The development of the FREEWAT platform was supported by the main needs and priorities expressed by relevant stakeholders from the water sector involved in the early stage of the project.Extensive testing on the platform is still going on and training material and six User Manuals were prepared to disseminate its use as a standard software for managing surface/sub-surface water quantity and quality dynamics under demand-driven and supply-constrained conditions. The testing phase also includes demonstration of the platform capabilities on 14 case studies at European scale and beyond, to address specific water management issues. Nine of them are devoted to the application of EU water-related Directives, while the others address water management issues in the rural environment under the requirements of EU and/or national/local regulations. Beyond software testing, this demonstration is thought as an experiment on involving stakeholders in the formation of water plans yet during the technical phase of the analysis.

Conceptualization and characterization of a coastal multi-layered aquifer system in the Taranto Gulf (southern Italy)

In some Mediterranean karst areas, groundwater is often the only available supply for fresh water. Besides the contamination induced by human activities, coastal aquifers often suffer from the saltwater intrusion phenomenon, which can be enhanced by both extensive withdrawals and climatic changes. Establishing an effective set of regulatory and management measures to ensure the sustainability of coastal aquifers requires a deep knowledge about natural and anthropic stresses involved in groundwater dynamics. In this regard, a prior conceptualization of aquifer systems and a deeper characterization of balance terms through mathematical modeling are of paramount importance. In this paper, previous works on the three-dimensional hydrostratigraphic characterization and two-dimensional groundwater flow modeling at the regional scale for the Salento peninsula (southeastern Italy) are shown to provide a fundamental basis for an overall conceptualization of the multi-layered aquifer system of the Taranto Gulf (northwestern Salento). This is done by identifying source terms and providing a preliminary estimate of different balance terms, based on available data and information. Then, a further characterization will be provided using three-dimensional groundwater flow models and calibration techniques based on the solution of an inverse problem. As a result the hydraulic features of the deep karst aquifer can be mapped; the stresses due to human water-demanding activities and the occurrence of the saltwater intrusion phenomenon were analyzed and possible weaknesses of the conceptual and of the preliminary numerical model pointed out.

FREEWAT, a Free and Open Source, GIS-Integrated, Hydrological Modeling Platform: L. Foglia et al. Groundwater XX, no. X: XX-XX

Author(s): Foglia, Laura; Borsi, Iacopo; Mehl, Steffen; De Filippis, Giovanna; Cannata, Massimiliano; Vasquez-SuA±e, Enric; Criollo, Rotman; Rossetto, Rudy

Integrating free and open source tools and distributed modelling codes in GIS environment for data-based groundwater management

Abstract Integrating advanced simulation techniques and data analysis tools in a freeware Geographic Information System (GIS) provides a valuable contribution to the management of conjunctive use of groundwater (the worlds largest freshwater resource) and surface-water. To this aim, we describe here the FREEWAT (FREE and open source software tools for WATer resource management) platform. FREEWAT is a free and open source, QGIS-integrated interface for planning and management of water resources, with specific attention to groundwater. The FREEWAT platform couples the power of GIS geo-processing and post-processing tools in spatial data analysis with that of process-based simulation models. The FREEWAT environment allows storage of large spatial datasets, data management and visualization, and running of several distributed modelling codes (mainly belonging to the MODFLOW family). It simulates hydrologic and transport processes, and provides a database framework and visualization capabilities for hydrochemical analysis. Examples of real case study applications are provided.

Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf, southern Italy)

The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.RésuméL’évaluation de la fiabilité ou du caractère raisonné des modèles numériques d’écoulement d’eaux souterraines est. une tâche complexe, du fait des incertitudes sur les propriétés hydrodynamiques et les conditions aux limites et du manque de données de terrain de bonne qualité. Pour estimer la fiabilité d’un modèle, différentes techniques de calage sont couplées dans le but d’évaluer les effets de différente types de conditions aux limites sur l’écoulement des eaux souterraines dans un aquifère côtier multi-couches dans le Sud de l’Italie. En particulier, les approches tant directes qu’indirectes en vue d’une modélisation inverse sont rapprochées grâce au calage de l’un des paramètres les plus incertains, c’est. à dire la conductivité hydraulique de l’unité hydrostratigraphique profonde karstique. La méthodologie proposée ici, et appliquée à un cas d’étude réel, a confirmé que le choix des conditions aux limites est. l’un des aspects les plus critiques et les plus difficiles de la caractérisation d’un système hydrogéologique en ce qui concerne l’analyze conceptuelle ou la simulation numérique. Les tests pratiques conduits dans cette étude montrent que la caractérisation incorrecte des conditions aux limites empêche une convergence acceptable entre la réponse du modèle aux contraintes hydrauliques et le comportement du système naturel. De tels effets ont un impact négatif sur l’applicabilité du modèle numérique pour simuler la dynamique de l’eau souterraine dans des situations hydrogéologiques complexes. Ceci est. particulièrement important pour la gestion du système aquifère étudié dans ce travail, qui représente la seule ressource en eau douce disponible de l’aire d’étude et qui est. menacé par la surexploitation et l’intrusion d’eau salée.ResumenLa evaluación de la exactitud o razonabilidad de los modelos numéricos de flujo de agua subterránea es una tarea compleja, debido a las incertidumbres en las propiedades hidrodinámicas y las condiciones de los límites y la escasez de datos de campo de buena calidad. Para evaluar la confiabilidad del modelo se unen diferentes técnicas de calibración para evaluar los efectos de distintos tipos de condiciones de contorno en el flujo de agua subterránea en un acuífero costero multicapa en el sur de Italia. En particular, los enfoques directos e indirectos para el modelado inverso se unieron mediante la calibración de uno de los parámetros más inciertos, a saber, la conductividad hidráulica de la unidad hidroestratotigráfica kárstica profunda. La metodología propuesta aquí, y aplicada a un estudio de caso real, confirmó que la selección de condiciones de borde es uno de los aspectos más críticos y difíciles de la caracterización de un sistema de agua subterránea para el análisis conceptual o la simulación numérica. Las pruebas prácticas realizadas en este estudio muestran que la especificación incorrecta de las condiciones de contorno impide una coincidencia aceptable entre la respuesta del modelo a los esfuerzos hidráulicos y el comportamiento del sistema natural. Tales efectos tienen un impacto negativo en la aplicabilidad del modelado numérico para simular la dinámica del agua subterránea en situaciones hidrogeológicas complejas. Esto es particularmente importante para el manejo del sistema acuífero investigado en este trabajo, que representa el único recurso disponible de agua dulce del área de estudio, y está amenazado por la sobreexplotación y la intrusión de agua salada.摘要地下水流数值模型的精确性或合理性评估是一个复杂的工作,这是因为水力特性和边界条件不确定,以及缺乏高质量的野外数据。为了评价模型可靠性,结合不同校正技术评估了不同种类边界条件对意大利南部沿海多层含水层中地下水流的影响。尤其是,通过多数不确定参数的一种参数、即岩溶深层水文地层单元的水力传导率的校准把反演模拟的直接和间接方法结合在一起。这里提出的方法及应用到实际案例的方法证实,边界条件的选择是概念分析或数值模拟中描述地下水系统特征最关键和最难的方面之一。本研究进行的实际试验显示,边界条件的错误确定阻止模型对水力压力的响应与天然系统特性之间的可接受的匹配。这样的效果对模拟复杂水文地质条件下地下水动力学的数值模拟的适用性具有负面影响。这对于本研究中所调查的含水层系统的管理尤为重要,这个含水层系统代表研究区内唯一可利用的淡水资源,受到了超采和海水入侵的威胁。RiassuntoLa valutazione dell’accuratezza e dell’affidabilità di un modello numerico per la simulazione del flusso delle Acque Sotterranee è particolarmente complessa, a causa delle incertezze legate alla definizione delle proprietà idrodinamiche e delle condizioni al contorno e alla scarsità di dati di buona qualità. Per valutare l’affidabilità del modello presentato in questa pubblicazione sono state utilizzate congiuntamente diverse tecniche di calibrazione, per valutare gli effetti di diversi tipi di condizioni al contorno sul flusso idrico simulato in un acquifero costiero multi-strato nell’area di Taranto (Italia meridionale). In particolare, sono stati utilizzati congiuntamente un metodo diretto e un metodo indiretto per la risoluzione di problemi inversi. L’utilizzo congiunto dei due metodi è stato possibile mediante la calibrazione di uno dei parametri maggiormente incerti, cioè la conducibilità idraulica del mezzo fratturato e carsico ospitante l’acquifero profondo. La metodologia proposta, e applicata ad un caso studio reale, ha confermato che la selezione delle condizioni al contorno è tra gli aspetti più critici nella caratterizzazione di un sistema acquifero per la definizione di un modello concettuale o l’implementazione di un modello numerico. Le prove presentate in questa pubblicazione mostrano che una definizione inappropriata delle condizioni al contorno previene una corrispondenza ottimale tra la risposta del modello a determinati stress idraulici e il comportamento del sistema naturale. Ciò ha un effetto negativo sull’applicabilità degli strumenti modellistici per la simulazione del flusso idrico in complessi sistemi idrogeologici. Questo aspetto risulta particolarmente importante per la gestione del sistema acquifero in esame, che rappresenta la sola riserva di acqua dolce nell’area e risulta minacciata da sovrasfruttamento e dall’ingressione di acqua marina.ResumoA avaliação da acurácia ou razoabilidade dos modelos numéricos de águas subterrâneas é uma tarefa complexa, devido às incertezas nas propriedades hidrodinâmicas e condições de contorno e à escassez de dados de campo com boa qualidade. Para estimar a confiabilidade, diferentes técnicas de calibração estão unidas com o objetivo de avaliar o efeito de diferentes tipos de condições de contorno no escoamento das águas subterrâneas em um aquífero costeiro de várias camadas no sul da Itália. Em particular, tanto as abordagens direta e indireta para modelagem inversa foram unidas por meio da calibração de um dos parâmetros mais incertos, chamado de condutividade hidráulica de unidades hidroestratigráficas cársticas profundas. A metodologia proposta aqui, e aplicada em um estudo de caso real, confirmou que a escolha das condições de contorno está entre um dos aspectos mais críticos e difíceis da caracterização de um sistema de águas subterrâneas para análise conceitual ou para a simulação numérica. Os testes práticos conduzidos neste estudo mostram que a especificação incorreta das condições de contorno evita uma correspondência aceitável entre a resposta do modelo em relação às tensões hidráulicas e o comportamento do sistema natural. Tais efeitos têm um impacto negativo na aplicabilidade da modelagem numérica para simular a dinâmica das águas subterrâneas em situações hidrogeológicas complexas. Isso é particularmente importante para o gerenciamento do sistema aquífero investigado neste estudo, o qual representa o único recurso de água doce disponível da área de estudo, e está ameaçado pela superexplotação e a intrusão salina.

Exposing high-school students to Geosciences through seminars, laboratory and field demonstrations

To familiarize high school students with the richness of geosciences and their practical applications, Universita degli Studi di Milano has been conducting a number of activities in co-operation with the Liceo G. Bruno (Melzo, MI, Italy). This contribution discusses the number of activities conducted including classroom seminars, laboratory experiments and in-the-field demonstrations.