Hydrogeological System Research Articles

Combination of geostatistics and self-organizing maps for the spatial analysis of groundwater level variations in complex hydrogeological systems

Successful modelling of the groundwater level variations in hydrogeological systems in complex formations considerably depends on spatial and temporal data availability and knowledge of the boundary conditions. Geostatistics plays an important role in model-related data analysis and preparation, but has specific limitations when the aquifer system is inhomogeneous. This study combines geostatistics with machine learning approaches to solve problems in complex aquifer systems. Herein, the emphasis is given to cases where the available dataset is large and randomly distributed in the different aquifer types of the hydrogeological system. Self-Organizing Maps can be applied to identify locally similar input data, to substitute the usually uncertain correlation length of the variogram model that estimates the correlated neighborhood, and then by means of Transgaussian Kriging to estimate the bias corrected spatial distribution of groundwater level. The proposed methodology was tested on a large dataset of groundwater level data in a complex hydrogeological area. The obtained results have shown a significant improvement compared to the ones obtained by classical geostatistical approaches.

Geological and Morphometric Characteristics of Quaternary Pyroclastic Aquifers in Salak and Pangrango Stratovolcano.

Indonesia is located in a subduction zone formed by the collision of continental and oceanic plates. Many volcanoes form as a result of these conditions along the arc. Springs on the volcano's slopes are widely used for domestic, irrigation, and industry water use. Investigating the characteristics of aquifers and springs is essential to ensure groundwater sustainability by providing a robust geological framework. Meanwhile, groundwater in a volcanic geological setting has good quality characteristics because of its occurrence process, which interacts with many minerals in pyroclastic rocks that act as aquifers. The study area is located in the Lido Catchment Area (LCA), which is situated between two distinct volcanic slopes. Geological and morphometric analysis at LCA is the basis of important information relating to its hydrogeological systems. The analysis of thin rock sections and parameters of the physical properties of water in groundwater springs supports our research. We applied a comprehensive geological and morphometric analysis to obtain detailed information about the aquifer. This study aimed to determine the characteristics of aquifers in pyroclastic rocks and their relationship to the formation of springs. From the research conducted, the characteristic of water can be distinguished based on the geological conditions of its constituents. There are 6 different lithological characteristics in the study area: polymictic breccia, monomictic breccia, lapilli, lapilli tuff, coarse tuff, and fine tuff. From the lithology variations obtained, breccia, lapilli, and coarse tuff can play a good role as aquifers. Geological correlations and groundwater systems in the study area show groups of superficial, mixed, and alteration springs. The system of water flows in aquifers through inter-grains or rock fractures. The types of springs in LCA are dominated by depression and fracture types. These results are fundamental information for understanding hydrogeological systems in future volcanic geological settings.

Environmental isotope constraints and hydrogeochemical evolution of groundwater in the semi-arid national capital environs of Delhi, India

Changes in hydrological regimes due to rapid urbanization and increasing anthropogenic stress on hydro-geological system creating an alarming condition for the management of ground water resources. Isotope and hydro-geochemical integrated approach has been used to determine the processes governing chemical composition of groundwater and the mechanism influencing the chemical composition of groundwater in National Capital Region (NCR), Delhi. The chemical evolution of groundwater has studied by using flow direction, hydro-chemical facies, bivariate plots of ionic ratios and saturation index. Stable isotopes and tritium are used to understand the recharge mechanism. Pollution index of groundwater (PIG) is also used to check the level of contamination in the groundwater. In total, 57 water samples were collected for water chemistry, 36 water samples for environmental isotopes and 13 samples for tritium measurement. The dominant water type is Ca-Mg-HCO3 and mixed water type. The dominant cation are Ca2+ > Na+ > Mg2+ > K+ and dominant anions are HCO3− > Cl− > SO42− > NO3−. The bicarbonate type water is dominant in quartzite, implies rapid and direct recharge through fracture and joints. Ionic ratios and saturation indices show that major processes controlling groundwater evolution are silicate hydrolysis and reverse cation exchange in the quartzite. Average values of δ2H and δ18O are −43.66 ‰ and −6.28‰. Stable isotopic ratio of groundwater of alluvium area falling on evaporation line, due to the prevailing semi-arid and arid climatic conditions, evaporation is the predominant factor affecting the chemistry of groundwater. The stable isotope shows that the groundwater in the quartzite is mostly meteoric in origin and acting as a recharge area for the nearby alluvium aquifer. Tritium results reveal that groundwater occurring in quartzite and alluvium aquifer in western parts are older than that of groundwater occurring in alluvium aquifer in the eastern parts.13% of groundwater samples are falling in very high pollution zone mainly occurring in alluvium aquifer that lies in the Eastern parts. It is inferred that alluvium aquifer (low lying) is having greater impact of anthropogenic activity than quartzite aquifer (high land).

Distribution of tritium-helium groundwater ages in a large Cenozoic sedimentary basin (North German Plain)

The travel time of groundwater plays a major role in the understanding of hydrogeological systems; however, large data sets necessary for regional studies of groundwater age are rare. In this study, a unique large data set of groundwater samples analysed for tritium and helium isotopes collected over the last 20 years from Cenozoic aquifers of the North German Plain is explored. Hereby, the variety of natural and technical influences on the tritium-helium age, including screen depth and length, groundwater recharge rate and climatic effects, are investigated. To a sampling depth of ~40 m below ground level, the median tritium-helium age increases almost linearly with depth, reaching a maximum of 40 years. Below, the portion of older, tritium-free water rises. The tritium-helium ages of the tritium-bearing portion increase only slightly to a maximum of about 46 years. The depth distribution of the tritium-helium age shows a dependency on groundwater recharge rates. Considering the same depth level, younger ages are related to higher groundwater recharge rates as compared to groundwater that infiltrated in areas with lower recharge rates. This is especially observed for shallow depths. Tritium-helium ages younger than 40 years are reflected well in the atmospheric tritium input curves, while deviations from it can be related to anthropogenic influences such as input from nuclear power plants and irrigation with deep, tritium-poor groundwater. The regional distribution for shallow wells indicates increasing tritium-helium ages from west to east, corresponding to decreasing groundwater recharge rates due to the more continental climate in the east.

Impact of Dead Sea Halo-Karst Development on an Earthen Dike Rehabilitation Project

From the 1970s, the Dead Sea experienced severe halo-karstification and anthropogenic modifications. Progressively, but at an accelerating rate, subsidence, landslides, and sinkholes have increased in number and magnitude. The hazards’ triggering factors are the terminal lake level lowering at more than one meter per year and the dynamic equilibrium of the hydrogeological system. Over the Lisan peninsula, archived satellite images revealed the extent of the damaged areas. On 22 March 2000, the destruction of dike 19 represented a loss of 38 M USD. This is the most important event recorded since the beginning of the Dead Sea recession some 50 years ago. In 2018, a rehabilitation project of that dike started. This research analyses the viability of the reinstatement works. The advanced space borne radar interferometry technique is applied to map ground deformations before and during the project. This article reveals that the ongoing rehabilitation and reinstatement works of dike 19 are threatened by ongoing halo-karstification processes. Field observations and subsidence/uplift dynamics support this statement. The past experiences are taken into consideration to adapt industrial expansion strategies. However, the permeability of the salt pan floor could trigger a fast development of a karst system able to destroy the rehabilitated dike 19.

ГИДРОГЕОЛОГИЧЕСКоЕ СТРОЕНИЕ БУЗАЧИНСКОГО АРТЕЗИАНСКОГО БАССЕЙНА (ЗАПАДНЫЙ КАЗАХСТАН)

The largest structural element of the Buzachi structural-tectonic zone is the North Buzachi Uplift, which is limited from the south by the South Buzachi, and in the north and northeast by the Kultuk depressions. The Buzachi artesian basin is confined to the Cretaceous deposits of the Aptian–Turonian age. The physical properties and chemical composition of waters from productive strata are closely related to the conductive properties of sedimentary strata. The available hydrogeological materials for the area under consideration make it possible to single out two hydrogeological systems in the basin. The upper system is groundwater of Quaternary deposits. The lower system includes aquifers of the Jurassic, Lower Cretaceous and partly Upper Cretaceous (Cenomanian – Lower Turonian), and from above they are limited by Senonian and Paleogene beds with low conductive properties.

Application of a Multi-Criteria Approach for the Assessment of Groundwater Potential in the Basement Zone: A Case of Tamou (South West Niger)

The commune of Tamou, located in the Department of Say in Niger, occupies the southwestern part of the Liptako crystallophyllian basement domain. In this area, the problem of the drinking water supply of the populations is acute, because of the low flow rates of the drillings capturing the crystallophyllian formations and the Voltaian sandstones, the failure rates of the drillings are very high there. Therefore, the main objective of this study is to improve the knowledge of the areas potentially favorable for the implantation of drillings likely to give more satisfactory flow rates. The methodological approach, based on the collection of data (Landsat 7 ETM+ satellite imagery, borehole data, geological and topographical maps) and their processing by a combination of remote sensing and GIS tools and a field check, allowed the elaboration of maps of availability, accessibility and exploitability of the groundwater resources in the study area. The maps developed were analyzed with a Spatial Reference Hydrogeological Information System following the technique of aggregation by weighting to generate the map of productive drilling sites. The results show that the area is moderately rich in groundwater (58%) and that only 31% of the potential is exploitable. The groundwater potential map shows that 46% of the study area is suitable for drilling.

Drilling boreholes in sulphureous groundwater areas: elements of some case studies in Portugal

In Portugal there is a special market niche, which is the medical spa sector. These are supplied by special groundwater, being the sulphureous type water, the most frequent water in this activity. These waters essentially have a long geohydraulic circuit, associated to granite massifs, in confined to semi-confined aquifer systems of the fissural type, and natural discharge sites are often associated with structurally very complex areas, with faults sometimes of great thickness, that lead to sudden variations, from very fresh rock to clay. However, this situation is very favourable to unexpected collapses of the borehole under construction, with terrible problems to overcome, sometimes leading to involuntary deviations in the spatial position of the drilling in progress. On the other hand, because one of the current solutions is the use of cementations, associated with re-drilling, there is also the problem, of the difficulties of cement grouts in a common situation, not gaining strength, due to the chemical composition of sulphureous groundwater. It should be noted that these aquifer systems have the potential to provide natural hot water, when the boreholes reach great depths and can leverage geothermal uses, at the same time as uses in medical spas. Therefore, it is necessary to know these aquifer systems well, to lead to more efficient projects in the future. Therefore, in that sense, after presenting the typical chemical composition of the sulphureous groundwaters understudy, the experiences acquired in the drilling of some boreholes in Portugal, namely in the Carvalhal Medical Spa, Longroiva Medical Spa, Águas do Graben, Unhais da Serra Medical Spa, and the new mineral water of Granjal (Santa Comba Dão), are briefly presented. The comparison of the objectives defined at the beginning with the results obtained is generically presented, namely the depth of drilling, giving emphasis to the problems of collapse of the walls of the boreholes, cementing, additives, among others. At last, some final notes are presented in the sense that the drillings in this type of hydrogeological systems, in the future come to be increasingly efficient and reach greater depth, not only to acquire water with quality freer of interferences with fluids of superficial aquifers, but also, in the sense of reaching temperatures that make the use of geothermal energy viable.

Small-magnitude earthquakes triggering fluid vents in a pressurised CO2 system, Caprese Michelangelo (Central Italy)

The CO2-(N2)-rich pressurised Caprese Reservoir (Northern Apennines, central Italy) is a structural system controlled by a subsurface fold anticline. Mud volcano-like structures and cold gas seeps lie along steep, ∼NE-trending faults, which are intimately connected to the deep fluid reservoir. In August 2010, five vents erupted mud flows after a local, small magnitude seismic sequence (MLmax 3.2). Although the exact dates of such paroxysmal episodes are unknown, they occurred within 55 days after the main shocks. These eruptions are evidence of triggered responses of mud volcano-like vents induced by earthquakes with small magnitude (ML3.0–3.2). Static stresses at the erupted vents are negligible, thereby dynamic strain is inferred to be the sole triggering mechanism. The main earthquakes produced a near-vent peak ground velocity (PGV) of ∼0.5 cm s−1 (ML3.2) and ∼ 0.2 cm s−1 (ML3.0). Although small, they are similar to other PGV values that triggered eruptive events in similar systems worldwide. A potential triggering mechanism can be searched in the enhanced permeability of fluid pathways produced by the passage of seismic waves. Fluid pressurization within the antiformal-shaped Caprese Reservoir by seismic wave focusing can also have played a significant role. This implies that seismic waves carrying even small perturbing stresses have the ability to stimulate hydrogeological systems to produce eruptions. Furthermore, our investigations allowed to assess the relationship between distance and earthquake magnitude for an M ∼ 3 event, and corroborate the validity of some existing empirical triggering thresholds of mud volcano-like systems even in the case of small earthquake magnitudes.

Bayesian Model Averaging Ensemble Approach for Multi-Time-Ahead Groundwater Level Prediction Combining the GRACE, GLEAM, and GLDAS Data in Arid Areas

Accurate groundwater level (GWL) prediction is essential for the sustainable management of groundwater resources. However, the prediction of GWLs remains a challenge due to insufficient data and the complicated hydrogeological system. In this study, we investigated the ability of the Gravity Recovery and Climate Experiment (GRACE) satellite data, the Global Land Evaporation Amsterdam Model (GLEAM) data, the Global Land Data Assimilation System (GLDAS) data, and the publicly available meteorological data in 1-, 2-, and 3-month-ahead GWL prediction using three traditional machine learning models (extreme learning machine, ELM; support vector machine, SVR; and random forest, RF). Meanwhile, we further developed the Bayesian model averaging (BMA) by combining the ELM, SVR, and RF models to avoid the uncertainty of the single models and to improve the predicting accuracy. The validity of the forcing data and the BMA model were assessed for three GWL monitoring wells in the Zhangye Basin in Northwest China. The results indicated that the applied forcing data could be treated as validated inputs to predict the GWL up to 3 months ahead due to the achieved high accuracy of the machine learning models (NS > 0.55). The BMA model could significantly improve the performance of the single machine learning models. Overall, the BMA model reduced the RMSE of the ELM, SVR, and RF models in the testing period by about 13.75%, 24.01%, and 17.69%, respectively; while it improved the NS by about 8.32%, 16.13%, and 9.67% for 1-, 2-, and 3-month-ahead GWL prediction, respectively. The uncertainty analysis results also verified the reliability of the BMA model in multi-time-ahead GWL predicting. This highlighted the efficiency of the satellite data, satellite-based data, and publicly available data as substitute inputs in machine-learning-based GWL prediction, particularly for areas with insufficient or missing data. Meanwhile, the BMA ensemble strategy can serve as a powerful and reliable approach in multi-time-ahead GWL prediction when risk-based decision making is needed or a lack of relevant hydrogeological data impedes the application of the physical models.

Environmental Impact Assessment of the Subsurface in a Former W-Sn Mine: Integration of Geophysical Methodologies

Associated with the exploitation of metallic minerals in Europe during the 20th century, several mining areas were abandoned without adequate environmental intervention. Furthermore, these areas lack studies to characterize the impact of pollution on the hydrogeological system. The area surrounding the tungsten mine of Regoufe, in northern Portugal, is one such area exploited during the Second World War. The accumulation of sulfide-rich tailings may have caused an acid mine drainage (AMD), where the leaching processes caused by seepage water led to soil contamination, evidenced by its acid character and anomalous concentrations of some Potentially Toxic Elements (PTE) reported in previous studies. The present research proposes an innovative approach that seeks the integration of different geophysical techniques to characterize the impact of mining activity on the subsurface. Electrical resistivity (ER) and electromagnetic (EM) were used to measure subsurface electrical properties. In addition, seismic refraction and Multichannel Analysis of Surface Waves (MASW) were performed to characterize the geometry, depth, and geomechanical behavior of the soil and rock bodies. The integration of these techniques allowed the interpretation of hydrogeological sections and a 3D resistivity volume to gain insight into the distribution of potentially contaminating fluids and tailings material present in the mining valley.

QUANTITY AND QUALITY OF GROUNDWATER OF INTERMOUNTAIN BASIN OF KORÇA IN ALBANIA AND IMPLICATION FOR SUSTAINABLE MANAGEMENT

Korça intermountain basin is the largest of its kind in Albania and from the hydrogeological point of view represents a semiclosed intermountain basin developed in Pliocene-Holocene granular unconsolidated deposits, which maximal thickness is about 300 m. The aquifer consists of intergranular gravelly to sandy layers containing artesian groundwater and the drilling wells are free flowing on most of the basin surface. The main recharge of the intergranular aquifer comes mainly from the rivers and torrents flowing from mountain gorges around the Korça Plain. The natural groundwater drainage of Korça basin is realized through the vertical leakage in the area of the former Maliq marsh. Hydrochemistry of the aquifers show the presence of four main hydrochemical facies which are related mainly to the hydrochemistry of the recharge sources and to the solution processes and ion exchange. In the central part of the basin the water supply wells of the cities Korça and Maliq are located. The natural renewable groundwater resources of the basin are relatively restricted, but the volume resources (or static water resources) are abundant (about 1.1 × 10–9 m3). The perspective of their exploitation is very important, but respecting the “basin yield” concept that is defined as the maximum rate of withdrawal that can be sustained by the hydrogeological system of groundwater basin without causing unacceptable changes to any other environmental component of the basin. To face the problems related to the intensification of the groundwater pumping systematic observations of the hydraulic reaction of the basin and of the possible groundwater quality deterioration and other negative environmental impacts must be organized. The purpose of the present study is for the first time to analyze the abundant basin wide hydrogeological data and to evaluate: (1) geometry and hydraulic parameters of the aquifers: (2) groundwater hydrodynamic conditions; (3) their chemical composition and (4) the natural groundwater resources and the possibility to intensify the groundwater pumping in close relation to the environmental impact.

Effects of structure and volcanic stratigraphy on groundwater and surface water flow: Hat Creek basin, California, USA

Hydrogeologic systems in the southern Cascade Range in California (USA) develop in volcanic rocks where morphology, stratigraphy, extensional structures, and attendant basin geometry play a central role in groundwater flow paths, groundwater/surface-water interactions, and spring discharge locations. High-volume springs (greater than 3 m3/s) flow from basin-filling (<800 ka) volcanic rocks in the Hat Creek and Fall River tributaries and contribute approximately half of the average annual flow of the Pit River, the largest tributary to Shasta Lake. A hydrogeologic conceptual framework is constructed for the Hat Creek basin combining new geologic mapping, water-well lithologic logs, a database of active faults, LiDAR mapping of faults and volcanic landforms, streamflow measurements and airborne thermal infrared remote sensing of stream temperature. These data are used to integrate the geologic structure and the volcanic and volcaniclastic stratigraphy to create a three-dimensional interpretation of the hydrogeology in the basin. Two large streamflow gains from focused groundwater discharge near Big Spring and north of Sugarloaf Peak result from geologic barriers that restrict lateral groundwater flow and force water into Hat Creek. The inferred groundwater-flow barriers divide the aquifer system into at least three leaky compartments. The two downstream compartments lose streamflow in the upstream reaches (immediately downstream of the groundwater-flow barriers) and gain in downstream reaches with the greatest inflows immediately upstream of the barriers.

Modeling the groundwater level for an arid aquifer under different groundwater management scenarios

Groundwater is considered the only source of water in arid climate regions. Additionally, population growth is stressing the groundwater resources in the study area, especially in these regions leading to excess groundwater exploitation to meet the demands (domestic, and agricultural). Thus, the groundwater level may decline in the future causing a water scarcity problem. In order to overcome this problem, it is worth necessary to perform mitigation measures prior to raising the groundwater level by augmenting the groundwater in the hydrogeological system. Mitigation measures might be reducing the abstraction rate and installing new artificial recharge sites. To assess the potential of these measures, numerical modeling can be applied. Gaza strip aquifer was chosen as a case study due to the following reasons: arid aquifer, significantly stressed due to over-exploitation of groundwater. Different researchers have already proposed different management scenarios considering these mitigation measures, but most of them considered unreliable management scenarios to predict future groundwater. Some of them reduced the abstraction rate which will lead to the loss of agricultural lands. Whereas, the others increased the artificial recharge rate which is unfeasible to implement in the study area for the next 20 years. Hence, we applied numerical modeling in this article to predict the future groundwater level based on these mitigation measures taking into account reliable management scenarios according to the study area’s current situation . The results indicate that combining both reducing the abstraction rate and increasing the artificial recharge is so promising and they were compared with the latter obtained by the previous researchers.

Analytical strategies to measure gadolinium as a wastewater marker in surface and groundwater systems

The increasing use of gadolinium (Gd)-based contrast agents in magnetic resonance imaging and the recalcitrant behavior of Gd during municipal wastewater treatment have led to increased concentrations of the tracer in aquatic environments. These anthropogenic Gd emissions to wastewater and, subsequently, to surface and groundwater systems can be exploited to calculate groundwater travel times and mixing ratios, identify wastewater inputs, and calibrate groundwater models. However, analytical complexity, costs, and the time needed to directly measure anthropogenic inputs hinder the practical use of Gd. While direct measurements with inductively coupled plasma-mass spectrometry (ICP-MS) are highly efficient and feasible, only total Gd can be detected with this approach. In unknown hydrogeological systems, the differentiation between total, anthropogenic, and geogenic Gd by interpolating rare earth element patterns requires complex sample pre-treatment and pre-concentration. Direct measurements of Gd can be obtained using anion-exchange chromatography coupled to ICP-MS but the limit of quantification will be higher. Here we provide guidelines for selecting the optimal method for the analysis of Gd as a wastewater tracer in surface-groundwater systems.•The cost-effectiveness of existing analytical strategies to measure Gd when used as a wastewater tracer in surface-groundwater systems is addressed•A novel analytical strategy for direct determination of total Gd is presented

Automation of hydrogeological monitoring in mines: Methods and procedures

The article presents the concept of hydrogeological monitoring automation. The concept includes substantiation of monitoring systems with regard to permeation fluid dynamics and pore pressure distribution in 3D space; multilevel system; measurement process digitalization; promptness of data reading and transfer along telecommunication channels; dispatching control and interpretation of data on the induced and natural processes. A brief review of the modern theoretical framework to provide software/hardware for automation of a hydrogeological monitoring system is given. The approaches to determining the spatial boundaries, basic schemes of digital hydrogeological monitoring system arrangement, quantitative characteristics of recording devices at the monitoring stations and their location based on the degree of permeation flow deformation, as well as values of hydraulic gradients are recommended. The design features of the monitoring stations with their vertical, inclined and horizontal location, and their equipment with vibrating wire and strain gauges are presented. Measuring and telecommunication systems and the preferred field of application of vibrating wire and strain gauges are characterized. The methods of interpretation of digital hydrogeological monitoring data are described, in particular, division of pore pressure into hydrostatic, sub-hydrostatic, supra-hydrostatic. The recommendations are given for determining the values of hydraulic gradients, specific flow rates by monitoring station, reference profile and adjacent sections. The technological process of forecasting mechanical suffosion on the basis of the conceptual hydrogeological model and granulometric characteristics of uncohesive soils, graphical analysis of calculated and destructive hydraulic gradients, visualization of relationships between the calculated and destructive hydraulic gradients as maps and 3D isosurfaces are given. The research data are illustrated by a case-study of implementation and 3D representation of the predictive model of mechanical suffosion development in the tailings dump wall during its reconstruction up to the design elevation.

The hydrogeological karstic chalk system of the Yport springs (Seine-Maritime, France): investigations and resource exploitation

Abstract The small town of Yport in the northern part of the Pays de Caux, Normandy, is located on the shore of the English Channel between Étretat and Fécamp, at the outlet of a long dry valley that incises the chalk plateau. Eight hundred metres to the east, at the base of a cliff, is a cluster of springs, the ‘Fontaines d'Yport’, that emerge on the foreshore. Given their high discharge, measured at between 1 and 2.5 m 3 s −1 , the Le Havre authorities have been interested in these springs since the 1960s, in determining their origin, locating the karst conduit, developing them, and investigating the boundaries and vulnerability of the groundwater basin. Today, one third of the drinking water that supplies the Le Havre conurbation comes from the Yport wells, and investigations into their vulnerability and protection of their resource continues.

Application of geothermometric and hydrochemical methods to the investigation of thermal water of sources in the Northeastern of Algeria case of Setif city

Thermal water in northeastern Algeria (Setif) is a promising, sustainable resource of energy. To date, thermal water has not been used as a source of renewable energy in Algeria as no clear strategy has yet been developed for its use. In this study, eight samples of thermal water springs distributed within the area of Setif city were assessed, and their physical and chemical parameters (such as temperature, potential of hydrogen, electrical conductivity, and major ionic composition, including the K+, Na+, Ca2+, Mg2+, Cl−, SO42− and HCO3−) were measured. The results show that the temperature, potential of hydrogen and the electrical conductivity range between 30 and 52 °C (as measured in field), 6.92 and 7.35, and 1170 and 3160 µS/cm, respectively. Furthermore, the results indicate the existence of four hydrogeochemical facies dominating the hydrogeological system, which are SO4–Ca, Na–SO4, HCO3–Na and Cl–Na. The interaction with Jurassic limestone and the existence of evaporates along the upwelling system, respectively, control this. Due to the high variation of temperature, different geothermometers were used to estimate the geothermal reservoir temperature, the application of silica geothermometer (Quartz), because it is the most suitable in our case, gives temperatures estimated at the origin of the order of 80° C. It is higher than that measured at emergence, it reflects an average dissipation of 48° C. According to an analysis of these findings and the geothermal gradient in the area, two aquifer systems of the thermal complex are supplied by a reservoir that is stored in fissured Jurassic limestone that is more than 2600 m deep.

DNA-Based Tracers for the Characterization of Hydrogeological Systems—Recent Advances and New Frontiers

Tracer technologies based on naturally occurring substances or intentionally introduced compounds have a broad spectrum of applications in hydrogeological research and subsurface resource management. DNA (deoxyribonucleic acid)-based tracers, with unlimited unique variations and exceptional specificity, could potentially map the complex intricacies of subsurface flow networks in greater detail than traditional tracer methods. Here, we review recent advances in DNA-based tracer research involving modern culture-independent (i.e., molecular) measurement techniques for subsurface/flowpath characterization purposes. The two broad categories of DNA-based tracers, i.e., synthetic and naturally occurring, are further classified into four specific types: “naked DNA”, “encapsulated DNA”, “barcoding microbial communities”, and “indicator microbial communities”. We summarize and compare the basic methodological workflows for each type of DNA-based tracer and provide an overview of research developments in the past two decades, covering both laboratory/field-scale experiments and data interpretation methods. Finally, we highlight remaining questions and challenges for each type of DNA-based tracer in terms of practicality. Future research directions are also identified, including the application of emerging DNA tracer methods to a wider range of geological formations. Fundamental characteristics of these novel tracers need to be better understood, and their applicability under a broader range of engineering scenarios requires further validation.

Modelación multi-escala para la comprensión de los sistemas de flujo en un acuífero multicapa, Urabá-Colombia

Numerical modelling is a valuable tool which allows the characterisation of groundwater flow behaviour, its interactions, and the representation of different flow systems that occur in an aquifer. A regional-scale model requires general information to describe the flow trends. In contrast, local and intermediate-scale models require a more detailed knowledge of the flow boundaries, and more field information. In order to understand the groundwater flow in the aquifer system of the Eje Bananero del Urabá Antioqueño-Colombia, a multi-scale numerical model was implemented using MODFLOW®. This was performed following modelling protocols on three spatial scales in which the regional model provided the boundary conditions for the intermediate pattern, and the intermediate pattern for the local model. Finally, we represented some details that relate local and intermediate flows to regional flows, in which surface-groundwater interactions involving both shallow and deep ascending flows became evident. The results obtained in this work show the potential of multi-scale modelling as a tool to recognise and understand the groundwater flows in a layered aquifer system, which provide grounds for decision-making and proper management of hydrogeological systems.