Monitoring pumping test response in a fractured aquifer using ground-penetrating radar

This is the published version. Copyright 2010 by the American Geophysical Union. All rights reserved.Fractured aquifers present a number of problems when attempting to characterize flow on the well scale (less than 100 m). Standard hydraulic testing methods are expensive because of the need for installation of monitoring wells. Geophysical methods may suffer from a lack of resolution and nonunique solutions to data interpretation. We used ground-penetrating radar (GPR) surveying during a pumping test in a well-characterized, fractured, carbonate aquifer to monitor the response of a permeable subhorizontal fracture plane. We observed radar signal amplitude and waveform variations along a fracture reflector and correlated the radar signal response to changes in the water saturation of the fracture. Combining hydraulic measurements with GPR data and electromagnetic modeling, we identified an asymmetric fracture drainage pattern, provided accurate spatial information about the saturation of the fracture, and detected the presence of hydraulic boundaries. This study demonstrates that GPR surveying can be used successfully for real-time monitoring of pumping tests in fractured carbonate aquifers

Interaction between groundwater and wetlands, caused by open pit mining in southeast Buenos Aires, Argentina

This paper proposes to characterize the interactions between groundwater and the anthropogenic wetlands resulting from mining activities in Buenos Aires province, Argentina. The methodology consisted of measuring levels, hydrochemical and isotopic sampling, and construction of diagrams. Wetlands located on quartzites have a higher level than the groundwater in the transition zone to the porous aquifer. Wetlands have an isotopic enrichment relative to groundwater, suggesting the occurrence of evaporation processes. The origin of wetlands is water from the fractured aquifer whose thickness corresponds to the quarry face, and also from runoff

Hidrogeologia de aquíferos fraturados : aplicação de índices de consistência para a validação de modelos matemáticos geoespaciais

In hydrogeology, most studies using interpolators seek to estimate water table elevations, contaminant concentrations and aquifer vulnerability. The primary goal of this research was to evaluate which geospatial interpolator best suits six distinct hydrogeological parameters using nine consistency tests. Water wells were selected on a portion of the Serra Geral Fractured Aquifer System in Southern Brazil. This paper tested the Inverse Distance Weighted, Radial Basis Function, Ordinary kriging, Lognormal kriging and Cokriging methods. The results pointed out that the Inverse Distance Weighted showed better performance for the following parameters: potentiometric surface, first fracture flow zone and second fracture flow zone. Discharge, transmissivity, specific capacity and static level showed low consistency levels, greatly increasing the uncertainties associated with mathematical models for such parameters. Deterministic interpolators surpassed the stochastic interpolators in parameter estimates that presented strong spatial dependence and associations with lithostratigraphy and geomorphology. This research can contribute to future work on groundwater management and planning in fractured aquifers, since the use of different interpolation and consistency approaches to analyze and compare different hydrogeological parameters in a fractured aquifer system has not been found in the literature.Em hidrogeologia, a maioria dos estudos utilizando interpoladores buscam estimar os níveis do lençol freático, as concentrações de contaminantes e a vulnerabilidade de aquíferos. O objetivo principal desta pesquisa foi avaliar qual interpolador geoespacial melhor se adapta a cada um dos seis parâmetros hidrogeológicos selecionados, usando nove testes de consistência. Poços tubulares foram selecionados em uma porção do Sistema Aquífero Fraturado Serra Geral, no Sul do Brasil. Este artigo testou os métodos de Distância Inversa Ponderada, Função de Base Radial, Krigagem Ordinária, Krigagem Lognormal e Cokrigagem. Os resultados apontaram que a Distância Inversa Ponderada apresentou melhor desempenho para os seguintes parâmetros: superfície potenciométrica, primeira zona de fluxo de fratura e segunda zona de fluxo de fratura. A vazão, a transmissividade, a capacidade específica e o nível estático apresentaram baixos níveis de consistência, aumentando consideravelmente as incertezas associadas aos modelos matemáticos para tais parâmetros. Os interpoladores determinísticos superaram os interpoladores estocásticos nas estimativas de parâmetros que apresentaram forte dependência espacial e associação com a litoestratigrafia e a geomorfologia. Esta pesquisa pode contribuir para futuros trabalhos de gestão e planejamento de águas subterrâneas em aquíferos fraturados, uma vez que não foi encontrado na literatura o uso de diferentes métodos de interpolação e índices de consistência para analisar e comparar diversos parâmetros hidrogeológicos em um sistema aquífero fraturado

HYDROGEOLOGY OF FRACTURED AQUIFERS: APPLICATION OF CONSISTENCY INDEXES FOR THE VALIDATION OF GEOSPATIAL MATHEMATICAL MODELS: Hidrogeologia de aquíferos fraturados: aplicação de índices de consistência para validação de modelos matemáticos geoespaciais

In hydrogeology, most studies using interpolators seek to estimate water table elevations, contaminant concentrations and aquifer vulnerability. The primary goal of this research was to evaluate which geospatial interpolator best suits six distinct hydrogeological parameters using nine consistency tests. Water wells were selected on a portion of the Serra Geral Fractured Aquifer System in Southern Brazil. This paper tested the Inverse Distance Weighted, Radial Basis Function, Ordinary kriging, Lognormal kriging and Cokriging methods. The results pointed out that the Inverse Distance Weighted showed better performance for the following parameters: potentiometric surface, first fracture flow zone and second fracture flow zone. Discharge, transmissivity, specific capacity and static level showed low consistency levels, greatly increasing the uncertainties associated with mathematical models for such parameters. Deterministic interpolators surpassed the stochastic interpolators in parameter estimates that presented strong spatial dependence and associations with lithostratigraphy and geomorphology. This research can contribute to future work on groundwater management and planning in fractured aquifers, since the use of different interpolation and consistency approaches to analyse and compare different hydrogeological parameters in a fractured aquifer system has not been found in the literature

Unstable rock slope hydrogeology: insights from the large-scale study of western Argentera-Mercantour hillslopes (South-East France)

International audienceInventory of unstable hillslopes, hydrogeological mapping and hydrochemical characteristics of natural spring waters were used to determine the long-term relationships between groundwater and gravitational instabilities in the Upper Tinée Valley (South-East French Alps). Water chemistry and flow records allow to propose a conceptual model of water flow within unstable rocky slopes and to back-calculate the volume of infiltrated water and the flow velocity in the aquifers for different deformation states of the slopes. An increase in infiltrated yield, flow velocity and porosity is observed and linked to collapsed and toppled structures in the upper parts of the hillslopes. In these areas, perched aquifers take place in the reworked media. When a large landslide occurs, it modifies the geometry of the slope and bypasses the perched flows down to the foot of the slope. With long-term continuous slope deformation, the associated effect between water flows and slope destabilization changes. In the fractured rock, the coupled effect corresponds to rising water pressures with limited volumes of infiltrated water; in the more fractured and permeable collapsed and toppled areas, the volumes of infiltrated water increase with a lower variation of water pressures

An Alternative BEM for Simulating the Flow Behavior of a Leaky Confined Fractured Aquifer With the Use of the Semianalytical Approach

This work is supported by the National Major Research Program for Science and Technology of China (Nos. 2017ZX05063 and 2017ZX05037) and the National Natural Science Foundation of China (No. 51674227). The data used in this paper can be downloaded from the Zenodo website (https://doi.org/10.5281/zenodo.3519950).Peer reviewedPublisher PD

Groundwater protection in fractured media: a vulnerability-based approach for delineating protection zones in Switzerland

A vulnerability-based approach for delineating groundwater protection zones around springs in fractured media has been developed to implement Swiss water-protection regulations. It takes into consideration the diversity of hydrogeological conditions observed in fractured aquifers and provides individual solutions for each type of setting. A decision process allows for selecting one of three methods, depending on the spring vulnerability and the heterogeneity of the aquifer. At the first stage, an evaluation of spring vulnerability is required, which is essentially based on spring hydrographs and groundwater quality monitoring. In case of a low vulnerability of the spring, a simplified method using a fixed radius approach ("distance method”) is applied. For vulnerable springs, additional investigations must be completed during a second stage to better characterize the aquifer properties, especially in terms of heterogeneity. This second stage includes a detailed hydrogeological survey and tracer testing. If the aquifer is assessed as slightly heterogeneous, the delineation of protection zones is performed using a calculated radius approach based on tracer test results ("isochrone method”). If the heterogeneity is high, a groundwater vulnerability mapping method is applied ("DISCO method”), based on evaluating discontinuities, protective cover and runoff parameters. Each method is illustrated by a case stud

Geodetic tools for hydrogeological surveys: 3D-displacements above a fractured aquifer from GPS time series

International audienceDeep porous reservoirs are subject to charge and discharge of fluids (oil, gas or water), either naturally or induced by human exploitation. This leads to a variation in pressure inside the reservoir and consequently to a deformation of the overlying material. The knowledge of the ground surface displacements allows inferring the fluid migrations and the hydromechanical properties in the porous reservoir. Different kinds of geodetic tools are able to measure this ground deformation: GPS, radar interferometry InSAR, tiltmeters or leveling. Each of them has its own spatial and time characteristics and accuracies that conduct to different kind of applications. After a review of the geodetic studies applied to hydrogeological processes, we describe two examples of GPS time series measurements above the granitic fractured aquifer of Ploemeur, located in French Brittany. These time series records the 3D-displacements induced by the sum of different processes. In this site, the involved processes are mainly the ground deformation related to piezometric level variations in the aquifer that we are looking for and the ocean tide loading that can reach several centimeters in the study area. We present the protocol of the GPS data survey and the processing strategy applied to extract the effect of hydrogeological process with sufficient accuracy. Two different experiments were studied: the long term deformation corresponding to seasonal hydrological cycle and the short term deformation associated to a pumping test. For a same variation in piezometric levels, the vertical ground displacements show larger amplitude for long term signal than for short one, indicating a behavior depending on the duration of the hydrogeological load. This difference of reactivity in time can be related to the heterogeneity of the studied aquifer. Finally, this work shows that geodetic measurements provide important constraints for characterizing aquifer-system response