Effect of volcanic dykes on coastal groundwater flow and saltwater intrusion : a field-scale multiphysics approach and parameter evaluation

Acknowledgments This research was primarily based on research grant‐aided by the Irish Department of Communications, Energy and Natural Resources under the National Geoscience Programme 2007–2013. It also benefited from complementary funding from the Scottish Alliance for Geoscience, Environment and Society (SAGES). We acknowledge the contribution in data acquisition of the MSc students in Environmental Engineering at Queen's University Belfast, the landowner for access to the inland fields and the Department of Geography, Archaeology and Paleoecology at QUB for provision of the tidal model of Belfast Lough. The data used are listed in the references, tables, and figures and are available from the corresponding author upon demand. We acknowledge the constructive comments by the Associate Editor and three reviewers, which helped in improving the final manuscript.Peer reviewedPublisher PD

Identification of the saline zone in a coastal aquifer using electrical tomography data and simulation

Δημοσίευση σε επιστημονικό περιοδικόSummarization: A novel approach that borrows methods commonly used in environmental geophysics was developed for obtaining the estimates of the aquifer parameters. Specifically, estimates of hydraulic conductivity were obtained from field measurements of the electrical resistivity while accounting for the karsticity of the geological formations in the area of study. Geophysically determined hydraulic conductivity estimates were introduced to a 3-D groundwater numerical simulator (Princeton Transport Code – PTC) to compute the hydraulic heads distribution of the area of interest. The calibration of the numerical model was obtained matching the hydraulic-heads predicted by the simulator with the hydraulic-heads measured at specific well locations. Simulated hydraulic-heads were used with the Chyben-Herzberg equation to approximate the position of the sharp freshwater/saltwater interface of the base of the water supply aquifer. The existence of the faults impacts the groundwater flow and the distribution of the freshwater/saltwater interface.Presented on: Water Resources Managemen

Geophysical survey at the Omalos Plateau, Chania, Crete

Summarization: This paper discusses the preliminary results of a geophysical survey that was carried out at the Omalos plateau in Chania, Crete. The geophysical survey included measurements of electrical tomography, electrical mapping, seismic refraction, georadar, VLF and gravity. The aim of this survey is to compare the results from different geophysical methods used in imaging dolines and karstic features. The processing of the measurements indicates three geoelectrical layers. The first layer of extremely high electrical resistivity is attributed to alluvial – dilluvial deposits. The second layer of very low electrical resistivity reflects mainly the presence of marls. Finally, the third geoelectrical layer outlines the carbonate bedrock, whose relief appears highly irregular. The comparison of all geophysical methods leads to the same results, concerning the detection of dolines and karstic anomalies at the Omalos plateau.Παρουσιάστηκε στο: Bulletin of the Geological Society of Greec

Calibration of seawater intrusion models: Inverse parameter estimation using surface electrical resistivity tomography and borehole data

Electrical resistivity tomography (ERT) can be used to constrain seawater intrusion models because of its high sensitivity to total dissolved solid contents (TDS) in groundwater and its relatively high lateral coverage. However, the spatial variability of resolution in electrical imaging may prevent the correct recovery of the desired hydrochemical properties such as salt mass fraction. This paper presents a sequential approach to evaluate the feasibility of identifying hydraulic conductivity and dispersivity in density-dependent flow and transport models from surface ERT-derived mass fraction. In the course of this study, geophysical inversion was performed by using a smoothness constraint Tikhonov approach, whereas the hydrological inversion was performed using a gradient-based Levenberg-Marquardt algorithm. Two synthetic benchmarks were tested. They represent a pumping experiment in a homogeneous and heterogeneous coastal aquifer, respectively. These simulations demonstrated that only the lower salt mass fraction of the seawater-freshwater transition zone can be recovered for different times. This ability has here been quantified in terms of cumulative sensitivity and our study has further demonstrated that the mismatch between the targeted and the recovered salt mass fraction occurs from a certain threshold. We were additionally able to explore the capability of sensitivity-filtered ERT images using ground surface data only to recover (in both synthetic cases) the hydraulic conductivity while the dispersivity is more difficult to estimate. We attribute the latter mainly to the lack of ERT-derived data at depth (where resolution is poorer) as well as to the smoothing effect of the ERT inversion

Geophysical survey at the Omalos Plateau, Chania, Crete

Μη διαθέσιμη περίληψηNot available summarizationPresented on