Laura Foglia

Practical Use of Computationally Frugal Model Analysis Methods

Three challenges compromise the utility of mathematical models of groundwater and other environmental systems: (1) a dizzying array of model analysis methods and metrics make it difficult to compare evaluations of model adequacy, sensitivity, and uncertainty; (2) the high computational demands of many popular model analysis methods (requiring 1000s, 10,000 s, or more model runs) make them difficult to apply to complex models; and (3) many models are plagued by unrealistic nonlinearities arising from the numerical model formulation and implementation. This study proposes a strategy to address these challenges through a careful combination of model analysis and implementation methods. In this strategy, computationally frugal model analysis methods (often requiring a few dozen parallelizable model runs) play a major role, and computationally demanding methods are used for problems where (relatively) inexpensive diagnostics suggest the frugal methods are unreliable. We also argue in favor of detecting and, where possible, eliminating unrealistic model nonlinearities-this increases the realism of the model itself and facilitates the application of frugal methods. Literature examples are used to demonstrate the use of frugal methods and associated diagnostics. We suggest that the strategy proposed in this paper would allow the environmental sciences community to achieve greater transparency and falsifiability of environmental models, and obtain greater scientific insight from ongoing and future modeling efforts.

FREEWAT: FREE and open source software tools for WATer resource management

FREEWAT is an HORIZON 2020 project financed by the EU Commission under the call WATER INNOVATION: BOOSTING ITS VALUE FOR EUROPE. FREEWAT main result will be an open source and public domain GIS integrated modelling environment for the simulation of water quantity and quality in surface water and groundwater with an integrated water management and planning module. FREEWAT aims at promoting water resource management by simplifying the application of the Water Framework Directive and other EU water related Directives. Specific objectives of the FREEWAT project are: to coordinate previous EU and national funded research to integrate existing software modules for water management in a single environment into the GIS based FREEWAT; to support the FREEWAT application in an innovative participatory approach gathering technical staff and relevant stakeholders (in primis policy and decision makers) in designing scenarios for the proper application of water policies.The open source characteristics of the platform allow to consider this an initiative ad includendum (looking for inclusion of other entities), as further research institutions, private developers etc. may contribute to the platform development.Through creating a common environment among water research/professionals, policy makers and implementers, FREEWAT main impact will be on enhancing science- and participatory approach and evidence-based decision making in water resource management, hence producing relevant and appropriate outcomes for policy implementation. The Consortium is constituted by partners from various water sectors from 10 EU countries, plus Turkey and Ukraine. Synergies with the UNESCO HOPE initiative on free and open source software in water management greatly boost the value of the project. Large stakeholders involvement is thought to guarantee results dissemination and exploitation.

Environmental and socio-economic methodologies and solutions towards integrated water resources management

Semi-arid regions are facing the challenge of managing water resources under conditions of increasing scarcity and drought. These are recently pressured by the impact of climate change favoring the shifting from using surface water to groundwater without taking sustainability issues into account. Likewise, water scarcity raises the competition for water among users, increasing the risk of social conflicts, as the availability of fresh water in sufficient quality and quantity is already one of the major factors limiting socio-economic development. In terms of hydrology, semi-arid regions are characterized by very complex hydro- and hydrogeological systems. The complexity of the water cycle contrasts strongly with the poor data availability, (1) which limits the number of analysis techniques and methods available to researchers, (2) limits the accuracy of models and predictions, and (3) consequently challenges the capabilities to develop appropriate management measures to mitigate or adapt the environment to scarcity and drought conditions. Integrated water resources management is a holistic approach to focus on both environmental as well as on socio-economic factors influencing water availability and supply. The management approaches and solutions adopted, e.g. in form of decision support for specific water resources systems, are often highly specific for individual case studies.

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.

Effect of different transport observations on inverse modeling results: case study of a long-term groundwater tracer test monitored at high resolution

Conservative tracer experiments can provide information useful for characterizing various subsurface transport properties. This study examines the effectiveness of three different types of transport observations for sensitivity analysis and parameter estimation of a three-dimensional site-specific groundwater flow and transport model: conservative tracer breakthrough curves (BTCs), first temporal moments of BTCs (m1), and tracer cumulative mass discharge (Md) through control planes combined with hydraulic head observations (h). High-resolution data obtained from a 410-day controlled field experiment at Vandenberg Air Force Base, California (USA), have been used. In this experiment, bromide was injected to create two adjacent plumes monitored at six different transects (perpendicular to groundwater flow) with a total of 162 monitoring wells. A total of 133 different observations of transient hydraulic head, 1,158 of BTC concentration, 23 of first moment, and 36 of mass discharge were used for sensitivity analysis and parameter estimation of nine flow and transport parameters. The importance of each group of transport observations in estimating these parameters was evaluated using sensitivity analysis, and five out of nine parameters were calibrated against these data. Results showed the advantages of using temporal moment of conservative tracer BTCs and mass discharge as observations for inverse modeling.RésuméDes traçages conservatifs peuvent fournir des informations utiles pour caractériser diverses propriétés du déplacement en subsurface. Cette étude examine la portée de trois différents types d’observations sur le déplacement pour analyse de sensibilité et paramétrage d’un modèle tridimentionnel d’écoulement et de déplacement spécifiques sur un site donné : courbes d’apparition du traceur conservatif (BTCs), instant initial de BTCs (m1), et décharge cumulée du traceur (Md) par plans de contrôle combinés avec des observations piézométriques (h). Des données haute résolution obtenues lors d’une expérimentation contrôlée de 410 jours sur le terrain de la base US Airforce de Vandenberg, Californie, USA, ont été utilisées. Dans cette expérience, du brome a été injecté pour créer deux nuages adjacents contrôlés sur 6 sections transverses différentes (perpendiculaires à l’écoulement souterrain) avec un total de 162 forages de contrôle. Un total de 133 observations différentes de rabattement en régime transitoire, 1,158 de concentrations BTC, 23 de moment initial, et 36 décharge ont été utilisées pour analyse de sensibilité et estimation de neuf paramètres d’écoulement et de déplacement de l’eau souterraine. L’importance de chaque groupe d’observations de déplacement dans l’estimation de ces paramètres a été évaluée en utilisant une analyse de sensibilité, et cinq de ces neuf paramètres ont été calés sur ces données. Les résultats ont montré les avantages d’utiliser l’instant initial du traceur conservatif BTCs et le volume déchargé comme paramètres observés pour la modélisation inverse.ResumenLos experimentos de trazadores conservativos pueden proporcionar información útil para caracterizar varias propiedades de transporte subsuperficial. Este estudio examina la efectividad de tres diferentes tipos de observaciones de transporte para un análisis de sensibilidad y la estimación de los parámetros de un modelo de transporte y flujo de agua subterránea tridimensional en un sitio específico: curvas de ruptura del trazador conservativo (BTCs), primer momento temporal de BTCs (m1), y descarga de masa acumulativa del trazador (Md) a través de planes de control combinado con observaciones de carga hidráulica (h). Se han usado los datos de alta resolución obtenidos a partir de un experimento de campo controlado de 410 días en la Base de la Fuerza Aérea Vandenberg, California (EEUU). En este experimento, el bromuro fue inyectado para crear dos plumas adyacentes monitoreadas en seis transectas diferentes (perpendiculares al flujo de agua subterránea) con un total de 162 pozos de monitoreo. Se usaron un total de 133 diferentes observaciones de carga hidráulica transitoria, 1,158 de concentración de BTC, 23 de primer momento, y 36 de descarga de masa para el análisis de sensibilidad y estimación de los parámetros de nueve parámetros de flujo y transporte. Se evaluó la importancia de cada grupo de observaciones de transporte para estimar estos parámetros usando el análisis de sensibilidad, y cinco salidas de nueve parámetros fueron calibrados contra estos datos. Los resultados mostraron las ventajas de usar el momento temporal del trazador conservativo BTCs y la descarga de masa como observaciones para el modelado inverso.ResumoOs testes com traçadores conservativos podem fornecer informações úteis para a caraterização de várias propriedades de transporte subsuperficial. Este estudo analisa a eficácia de três tipos diferentes de observações de transporte para análise da sensibilidade e estimação de parâmetros de um modelo de escoamento subterrâneo e transporte tridimensional num local específico: curvas de ruptura (BTCs) de traçadores conservativos, primeiros momentos temporais das BTCs (m1) e a massa de descarga cumulativa do traçador (Md), através de planos de controlo combinados com observações do nível piezométrico (h). Foram usados dados de alta resolução obtidos num teste de campo controlado de 410 dias realizado na Base da Força Aérea de Vandenberg, na Califórnia (EUA). Nesta experiência, foi injetado brometo, de forma a criar duas plumas adjacentes monitorizadas em seis transetos diferentes (perpendiculares ao escoamento subterrâneo), num total de 162 furos de monitorização. Foram usadas um total de 133 observações diferentes de níveis piezométricos transitórios, 1,158 observações de concentração de BTC, 23 do primeiro momento e 36 de massa descarregada, para análise de sensibilidade e estimação de 9 parâmetros de escoamento e transporte. A importância de cada grupo de observações de transporte na estimação destes parâmetros foi avaliada através da análise de sensibilidade, e cinco dos nove parâmetros foram calibrados com estes dados. Os resultados mostraram as vantagens de se usar o momento temporal das BTCs dos traçadores conservativos e as massas de descarga como observações para a modelação inversa.

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.

Hydrodynamic analysis of a Mediterranean aquifer system with the use of hydrochemical and isotopical analysis as supporting tools

The management of groundwater resources in coastal environments within the Mediterranean basin has become of paramount importance, especially in the light of global changes. A typical example of such a hydrosystem is the Lavrio basin in Greece. This research site involves two aquifer types—granular and karstic formations—that are hydraulically interconnected. Furthermore, the proximity to the sea and the abstractions for irrigation and drinking water supply have led to the phenomenon of seawater intrusion. The present study aims at analyzing the hydraulic, hydrological, and hydrogeological conditions of the area by means of hydrochemical and isotopical data interpretation as supporting tools, which will inform and support the development of an integrated conceptual hydrogeological model of the area. Field investigations were conducted in order to collect piezometric and chemical data and use them to retrieve the quantitative and qualitative status of the local aquifer units. New interpretation of an older dataset gave an insight into how the karstic aquifer behaves in terms of hydraulics. The results have also demonstrated that there is a hydraulic connection between the different aquifers and the Mediterranean Sea, while natural recharge was quantified for both aquifer types.

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.