# Integrated Geophysical Methods for Shallow Aquifers Characterization and Modelling
## 2 Contributions  
Since the call for papers was announced in June 2019, a total of 11 manuscripts were received. After a rigorous review process, eight papers have been accepted for publication [1; 2; 3; 4; 5; 6; 7; 8]. To gain a better insight into the essence of the Special Issue, we offer brief highlights of the published papers below. The paper \"Integrated MASW and ERT Imaging for Geological Definition of an Unconfined Alluvial Aquifer Sustaining a Coastal Groundwater-Dependent Ecosystem in Southwest Portugal\" [1] integrates MASW and time-lapse ERT to define aquifer geometry and identify transient groundwater features of the Casalheira Stream Basin Holocene alluvial aquifer. This aquifer contributes to the Santo Andre Lagoon, which is part of a coastal GDE in southwest Portugal. This paper contributes a way to disambiguate geological structures in low electrical resistivity (ER) environments, such as coastal areas. The methodology serves to improve the design of shallow groundwater research. The paper \"Geophysical Characterization of Aquifers in Southeast Spain Using ERT, TDEM, and Vertical Seismic Reflection\" [2] assesses the effectiveness of different geophysical prospecting techniques to study the Loma de Ubeda Jurassic dolomite-confined thick aquifer in southern Spain. The VSR technique identified the high-amplitude seismic reflectors of the confined structure (aquifier) from the low-amplitude seismic reflectors of the clay-rich confining lower and upper structures. The ERT technique identified lateral changes in facies and small faults. The TDEM technique complemented the VSR and ERT techniques to widen the prospecting depth range. The paper \"Characterization of a Shallow Coastal Aquifer in the Framework of a Subsurface Storage and Soil Aquifer Treatment Project Using Electrical Resistivity Tomography (Port de la Selva, Spain)\" [3] couples ERT surveys with implicit modelling tools to identify aquifer geometry and characterize the saltwater intrusion in the Port de la Selva shallow alluvial aquifer in northeast Spain. With the aim to monitor the effects of water percolation through infiltration ponds, the proposed approaches can improve the commitment of stakeholders to the benefits of soil-aquifer treatment procedures for water reuse as an additional non-conventional water source. The paper \"Identifying Changes in Sediment Texture along an Ephemeral Gravel-Bed Stream Using Electrical Resistivity Tomography 2D and 3D\" [4] combines the ERT technique with datasets from borehole logs to analyze the inner geometry of channel cross-sections in a gravel-bed ephemeral stream in southeast Spain. The ERT models were correlated with sediment texture data, such as grain size distribution, effective grain size, sorting, and particle shape (Zingg's classification), in order to integrate the horizontal and vertical ER distributions into a 3D model, thus facilitating the identification of layers according to differential sediment supply at the basin scale. The paper \"Combining of MASW and GPR Imaging and Hydrogeological Surveys for the Groundwater Resource Evaluation in a Coastal Urban Area in Southern Spain\" [5] conceptualizes and evaluates the groundwater resource in Adra town in southern Spain, a coastal urban area hydrologically influenced by peri-urban irrigation agriculture. The study included a geological, hydrological, and hydrogeological data compilation, and MASW and GPR surveys to define shallow geological structures and some hydrogeological features. The paper also illustrates how urban groundwater reuse can alleviate the pressure on the currently overexploited regional aquifers. The paper \"Temporal and Spatial Groundwater Contamination Assessment Using Geophysical and Hydrochemical Methods: The Industrial Chemical Complex of Estarreja (Portugal) Case Study\" [6] presents data from several geophysical and hydrochemical campaigns carried out to monitor groundwater contamination in the industrial chemical complex of Estarreja in northern Portugal over a period of 30 years.