Groundwater Flow Conditions Research Articles

Environmental Impact of Synthetic Dyes on Groundwater in Malaysia: Sources, Distribution, Transport Mechanisms, and Mitigation Strategies

Synthetic dyes, extracted from natural sources like insects, plants, coal, and ochre, have become prevalent due to their advantages over natural dyes. However, their production has led to increased environmental pollution, particularly in groundwater. Groundwater contamination from synthetic dyes occurs through advection, dispersion, and retardation. This review aims to highlight the environmental impacts of synthetic dyes on groundwater, elucidate the mechanisms of dye transport, and propose effective strategies for monitoring and mitigating contamination. Urban runoff carries dyes from surfaces such as roofs, parking lots, and roads into stormwater systems, while agricultural runoff transports dyes from products like soil conditioners, fertilizers, and seed coatings into water bodies. In groundwater, dyes move through the aquifer via advection, dispersion, and retardation, all influenced by groundwater flow and geological conditions. The advection process involves the bulk movement of groundwater carrying dissolved dyes, while dispersion causes dyes to spread and dilute over time and distance. Retardation, which involves the adsorption of dye molecules onto soil particles, slows dye movement, prolonging their presence in groundwater. Understanding the sources, distribution, and movement of synthetic dyes in groundwater is crucial for developing strategies to protect water resources and reduce environmental and health impacts. The extensive use of dyes in industrial and domestic activities necessitates comprehensive monitoring and management to ensure sustainable groundwater quality.

Using hydrochemistry and stable isotopes to character the karst water environment in a cave site, South China

For cave sites located within the seasonal fluctuation zone of groundwater, obtaining a comprehensive understanding of the hydrogeological conditions and hydrochemical environment is of utmost importance in assessing the preservation of cultural deposits. However, due to the heterogeneity of karst development, the hydrochemical environment of the overburden karst water-bearing unit may exhibit complex variations. In this study, the characteristics of the water environment in a foot cave system and its surrounding aquifer were investigated at the Zengpiyan site, employing hydrochemistry, hydrogen and oxygen isotope analysis, as well as sulfate isotope analysis, in conjunction with the hydrogeological background. Based on the exposure of the karst cave and the groundwater flow conditions, the water-bearing medium was categorized into five types. The aquifer exhibited either an oxidation or reduction condition, with a distinct "dissolved oxygen hole" observed in the saturated zone of the cave site. Ion concentration analysis revealed that the groundwater was influenced by the prior accumulation of cinders in the upstream region, leading to sulfate contamination within the foot cave system. However, during the groundwater movement from upstream to downstream, the attenuation rate of pollutants displayed significant variations. Notably, the sulfate content was unusually low within the site cave. Hydrogen and oxygen isotopes provided insights into the differing circulation and movement velocities of groundwater within the local environment. Additionally, sulfate isotopes confirmed the sources of sulfate and the occurrence of bacterial sulfate reduction within the site cave. Consequently, an environmental zoning classification was established based on these analyses. Although the concentration of dissolved ions appears low in the anoxic area, it does not imply a diminished environmental risk. Under reducing conditions, these pollutants can be converted into more aggressive gases, posing a substantial threat to the preservation environment of cave sites. Therefore, sufficient attention should be given to this aspect in order to ensure adequate protection.

Adaptive management of borehole heat exchanger fields under transient groundwater flow conditions

Uncontrolled heat extraction by multiple interacting borehole heat exchangers (BHEs) in high-density energy-use districts can lead to undesirable thermal conditions in the subsurface which can affect both system performance and regulatory compliance. The difficulty in controlling heat extraction arises in particular from predictive uncertainties, such as when forecasting trends in energy demand or groundwater flow. In this study, a combined simulation-calibration-optimization framework is introduced to consider BHE fields with the presence of a transient groundwater flow regime. In the first part, a semi-analytical modeling technique is proposed based on temporal superpositioning of variable flow conditions. Two synthetic case studies verify its accuracy under different groundwater fluctuation patterns. The mean absolute error of the proposed model in comparison to numerical calculation does not exceed 0.18 K over ten years of operation. In the second part, the model is augmented by a parameter estimation algorithm that is employed for continuous model updating. The benefit of resolving transient flow conditions is demonstrated by using this approach for monthly optimization of individual BHE heat extraction. The result of dynamic optimization compared to a synthetic case without calibration shows a 10 % lower imposed temperature change in the subsurface.

Shoreline barriers may amplify coastal groundwater hazards with sea-level rise

Subsurface barriers have been proposed to protect coastal aquifers from sea-level rise induced seawater intrusion, but the potential for groundwater emergence near subsurface barriers remains unknown. Here, we investigated how emergence changes groundwater flow conditions and influences the protective performance of subsurface barriers with sea-level rise. We tested the subterranean consequences of sea-level rise for cutoff walls and subsurface dams with cross-shore groundwater flow and salt transport models, investigating how barrier design, aquifer properties, and hydrological conditions control the potential for emergence, groundwater partitioning at the barrier, and seawater intrusion with sea-level rise. We find that most subsurface infrastructure cannot prevent seawater intrusion and emergence simultaneously. Subsurface dams spanning more than half of the aquifer thickness created emergence hazards and subsequent groundwater partitioning for all scenarios tested. Cutoff walls were less effective at reducing seawater intrusion for all opening sizes but could reduce the emergence potential compared to similarly sized subsurface dams. Our results demonstrate the challenging trade-offs in mitigating the coastal groundwater hazards of seawater intrusion and emergence with sea-level rise, where groundwater flooding inland of protective infrastructure would require combinations of subsurface impoundments and other mitigation techniques, such as pumping or drains.

Effect of groundwater dynamics in rain-induced landslides: centrifuge and numerical study

Landslides are a multifaceted phenomenon triggered by rainfall infiltration as a consequence of the decrease in effective stress upon the development of porewater pressure. Although many studies concentrated only on rainfall infiltration as the source of the primary hydrological regime, the impact of groundwater dynamics has been relatively underexplored owing to its elusive nature. Field investigations after the landslide incidents provide insight into the influence of groundwater dynamics and speculate its effect as a secondary hydrological regime is immense. Therefore, this paper uses centrifuge modeling and numerical simulations to study groundwater dynamics in rain-induced landslides. Instrumented model slopes made of silty sand were tested to examine the hypothesis of pre-existing groundwater flow levels and surcharged groundwater flow conditions in rain-induced landslides. It was observed that swiftly rising porewater pressure along the soil–bedrock interface triggered landslides more rapidly under high groundwater flow and immediate surcharged groundwater flow conditions. Deformation analysis confirmed that a voluminous landslide could be expected if the role of groundwater dynamics is higher. A two–dimensional coupled hydromechanical finite element simulation was performed to back–analyze the experimental results and to discuss the failure mechanism. Upon validation, numerical simulation emphasized how the failure was accelerated under low-intensity rainfall if high groundwater flow exists. Furthermore, the study identified that surcharged flow profoundly affects landslide initiation if the slope has a low pre-existing groundwater flow. The outcomes highlighted that groundwater dynamics should be an integral part of the temporal predictability of landslides as they can also govern the magnitude of landslides.

Hydrogeological characterization of low permeability medium for conceptualization of a mine site in Eastern Turkey

The mining site in Eastern Anatolia of Turkey were encounter a significant risk of slope instability within the operational area. One of the processes that govern slope stability is the pore water pressure distribution. The conceptualization and characterization of porous media serve as fundamental prerequisites for the implementation of numerical methods aimed at predicting pore water distribution. This study aims to characterize the hydrogeological properties of water bearing rocks in the active mining site in Eastern Anatolia of Turkey. A total of 21 wells and drill holes were drilled in the study area to conduct in-situ tests, monitoring, and sampling. The large diameter wells drilled in surrounding the carbonate rocks were to determine the groundwater flow and boundary conditions and also wells tapped metasediments and diorite unit for hydraulic testing. The lugeon tests and installation of vibrating wire piezometers were carried out at small diameter drill holes to obtain localized hydraulic conductivity of metasediments and diorite at different depths and monitoring pore water pressure distribution along some critical cross-sections. The results obtained from these tests are used for developing hydrogeological conceptual model for groundwater flow. The results of in-situ tests show that the metasediment and diorite units act as a single hydrostratigraphic unit. The metasediments and diorite have high total porosity and low specific yield indicating that the pore water is retained by electrostatic forces in the medium and it resists flow due to low hydraulic conductivity. The vertical variation in hydraulic conductivity values indicates that the medium is highly heterogeneous.

Investigation on heat transfer performance of energy diaphragm walls under groundwater flow condition

The flow of groundwater affects the transport of heat, subsequently impacting the heat transfer performance of energy diaphragm walls. To investigate the effect of groundwater flow on the thermal performance of energy diaphragm walls in the actual project, a three-dimensional finite element model of the thermo-hydro coupling was established. This model's accuracy was confirmed using in-situ experimental data. Subsequent analyses explored the influence of groundwater flow velocity on the long-term heat transfer efficiency of energy diaphragm walls and the temperature field distribution in both the wall and adjacent soil during winter/summer cyclical operations. Studies have shown that the increase of groundwater flow velocity can promote the migration of heat accumulated in the wall and in the soil around the wall to a position farther away from the wall along the flow direction, thereby promoting the long-term heat exchange efficiency of the thermo-active diaphragm walls. Moreover, as winter and summer operating conditions transition, the previously accumulated heat in the wall and surrounding soil aids in boosting the current mode's heat exchange efficiency. In addition, groundwater flow also facilitates the movement of heat accumulated at the bottom of the excavation face, allowing the ground's temperature field to stabilize faster. This indirectly bolsters the heat exchange efficiency of the energy diaphragm walls. The research results may enrich the understanding of the heat transfer behavior of energy diaphragm walls under actual working conditions.

Impact of a CO2 leak on the release of major and trace elements according to groundwater flow conditions in a shallow freshwater carbonate aquifer: In-situ experiments and modelling

To investigate the role of hydrogeological conditions on the release of major and trace elements during CO2 leakage occurring in shallow freshwater aquifers in a CO2 Capture and Storage context, this paper compares the results of two in-situ CO2 leakage experiments. These experiments were carried out in a shallow freshwater carbonated aquifer located in Saint-Emilion, France, during both low and high-water levels periods. In both experiments, 200 L of carbonated water were injected into a well and groundwater monitoring was carried out downstream.Due to the physical heterogeneity of the aquifer at a small scale, the CO2-rich water plume did not follow the same flow path between the two hydrogeological periods, thus highlighting preferential pathways. It was observed that geochemical changes were not of the same intensity. The concentrations of Ca2+, HCO3−, Mg2+, Fe, Mn, As, Co, Cu, Ba, Sr and V increased during the low-water level experiment while the measured concentrations only reflected the dilution of the gasified water injected during the high-water level period.

Groundwater dilution and flow conditions in sulfuric acid caves: the case study of Frasassi (Italy)

This study analyzes the dilution process of the sulfidic groundwater in the Frasassi caves due to the recharge of O2-rich freshwater and its influence on the sulfuric acid speleogenesis and morphogenesis. The drainage pattern and the seasonal changes of the chemo-physical characteristics of the groundwater through a year-long monitoring and the measurements of the groundwater levels are presented. The inflow of water infiltrating from the karst surface influenced the sulfidic groundwater parameters, reflecting the seasonal meteoric cycle. On the contrary, the Sentino River, which represents the local base level, directly influenced the groundwater only in the most external part of the cave. The water level measurements evidenced a low hydraulic gradient (~3‰), due to the high karstification, and also some differences in the permeability depending on the drainage direction. Most cave pools are isolated on the surface and connected to each other through a network of submerged passages. In the present conditions, a surface layer of bicarbonate water forms above the sulfidic water in a large part of the cave, where it impedes subaerial corrosion by released acidic gases. Conversely, the distribution of residual gypsum deposits and corrosional wall features in the upper old cave levels demonstrate that large interfaces between sulfidic water and cave atmosphere existed during some periods of the cave history. Here, the release of acidic gases (CO2 and H2S) and the production of H2SO4 from H2S oxidation caused the widespread subaerial corrosion which significantly contributed to the morphogenesis. The comparison between these residual morphologies and the active processes shows that morphogenesis in the cave has evolved through time, influenced by hydrodynamic conditions, in turn depending on the general morphological and hydrogeological setting of the whole karst area.

Effect of groundwater flow on thermal performance of SBTES systems

In this study the influence of different groundwater flow conditions on the short- and long-term thermal performance of SBTES system is studied. Numerical analyses of a SBTES system are performed using COMSOL with four groundwater table depths and with four groundwater velocities. The study evaluates the thermal performance of SBTES in terms of the average temperature, heat stored, and system efficiency over a 10-year operational period. The results indicate that high groundwater velocity (1 × 10−5 m s−1) has a detrimental effect on the thermal performance of SBTES, causing significant reduction in the stored heat. Medium groundwater velocity (1 × 10−7 m s−1) with the groundwater table at half the depth of SBTES has an insignificant effect during the initial years of operation but causes significant reduction in heat stored over the long term. The study also highlights the potential of heat loss resulting from high velocity groundwater flow taking place below the SBTES. The findings suggest that groundwater flow plays a critical role in the thermal performance of SBTES, and long-term analysis is necessary to evaluate the impact.

Electrical Resistivity Tomography (ERT) Monitoring of Groundwater Flow Condition Surround Deep Excavation in Slope Area

Indonesia is a country with lots of mountain and hills, conducting deep excavation around slope areas will affect the groundwater. Deep excavation will change the groundwater table and hydrogeological condition. In order to monitoring the groundwater flow from the deep excavation in slope area, Electrical Resistivity Tomography used to monitoring the area surround the deep excavation project. The resistivity distribution in the area can be determined by knowing the condition of the soil around the deep excavation project through ERT (Electrical Resistivity Tomography). By utilizing passive ERT, vital parameters, such as porosity and volumetric water content, can be estimated, enabling the calculation of water saturation maps from inverted resistivity values. The resistivity conditions of the soil are continuously monitored, leading to the identification of patterns in soil resistivity movement, and the detection of potential instabilities at the boundaries between areas with varying water saturation levels.

Potenential for thermal energy from Tunnels beneath Manchester and Crewe: a case study

potenential for thermal energy from Tunnels beneath Manchester and Crewe: a case study

Influence of site characteristics on the performance of shallow borehole heat exchanger arrays: A sensitivity analysis

Using borehole heat exchangers (BHE) to extract shallow geothermal energy has grown rapidly in recent years. How to maintain a long-term balanced, sustainable operation of the BHE arrays becomes a key issue. Site characteristics, including hydrogeological and geothermal conditions as well as spatial distribution of subsurface physical parameters, are generally idealized or partly neglected in practice. To investigate the consequences of such simplifications, a 3D model, based on data from a planned real site, is established to consider groundwater flow, subsurface heterogeneity, and various hydrogeothermal boundary conditions. After verifying the model, a sensitivity analysis is conducted. Nine factors regarding site characteristics are selected, including Darcy flux in the aquifer, thermal conductivity and volumetric heat capacity of the ground, groundwater depth, thermal and hydraulic heterogeneity, geothermal gradient, heat transfer coefficient on the ground surface and seasonal rainfall. Sensitivity results indicate that the annual total heat production is most sensitive to geothermal gradient, followed by Darcy flux, both of which have positive effects. Groundwater depth and heat transfer coefficient have negative effects on annual heat production. Compared to thermal heterogeneity and rainfall, the influence of hydraulic heterogeneity is higher. Uncertainty of annual heat production due to various Peclet numbers is quantified through regression analysis.

Application of 3D numerical simulations to forecast mine seepage and groundwater flow conditions with respect to progressive coal mining activity

Application of 3D numerical simulations to forecast mine seepage and groundwater flow conditions with respect to progressive coal mining activity

Paleohydrogeology of the Horonobe area, Northern Hokkaido, Japan: Groundwater flow conditions during glacial and postglacial periods estimated from chemical and isotopic data for fracture and pore water

Understanding the difference in groundwater flow between glacial and interglacial periods is crucial for predicting the impact of future climate changes on groundwater movement. This study assesses the difference in groundwater flow between the last glacial period (LGP) and the postglacial period (PGP) in fractured mudstones of the Horonobe area, Japan, by combining the data for stable isotopes (δD and δ18O) and Cl− concentration of fracture and pore waters with radiocarbon (14C) age. The isotopic compositions of fractures and pore waters indicate that groundwater at 28–250 m deep in a borehole closest to the recharge area comprises meteoric water, recharged under the same climates as the present. The fracture water has isotopic compositions more similar to meteoric water than the matrix pore water near the fracture. The 14C age of fracture water suggests meteoric water recharge during the PGP. At greater depths in the borehole and sampling points in other boreholes, the isotopic compositions indicate the mixing of glacial meteoric and altered connate water, with the fracture water having comparable isotopic compositions with the matrix pore water. The recharge timing of meteoric water is inferred to be the LGP or before based on 14C dating. These results suggest that the meteoric water recharged during the PGP flows at a shallow depth, whereas the meteoric water recharged during the LGP intruded to greater depths. This result is consistent with previous inferences from surface geophysical and geological surveys that the depths of local valleys during the LGP were greater by < 50 m than the present ones and enhanced the downward hydraulic gradient. Combining the chemical and isotopic compositions of groundwater with 14C age helps assess the groundwater flow during the LGP and PGP in fractured rocks.

A multistage model of preservation in fossil plants from the Llewellyn Formation (Pennsylvanian), St. Clair, Pennsylvania, U.S.A

Exceptionally preserved plant fossils from St. Clair, Pennsylvania, have long been part of museum and private collections. Fossil leaf fragments and stems from the underclay of the Buck Mountain Coal (Reading Anthracite Company quarry), lowest Llewellyn Formation (late Pennsylvanian, Virgilian), combine outer layers of coalified organic material (phytoleim) with strikingly white kaolinite, quartz, and the low-grade metamorphic mineral pyrophyllite in the interior. The surficial dark, coalified material appears to preserve the dense outer layers (cuticle, epidermis, and palisade layer) and some cells of the spongy mesophyll in the fossilized leaves. XRD spectra of separated phytoleim contain graphite peaks. Raman spectra with peaks near 1600 and 1320 cm−1 indicate that the phytoleim is composed of disordered graphitic material. ID/IG ratios from ca. 0.3 to 0.45 are consistent with greenschist facies metamorphic conditions forming the anthracite coal. The interior pyrophyllite is highly crystalline, with large crystals often oriented perpendicular to leaf surfaces. Hydrothermal formation of pyrophyllite requires relatively limited groundwater flow conditions and temperatures between ca. 275 and 350 °C. Although many fossil leaves are compressed, some are near their original thickness. We infer that the remains were replaced prior to significant burial and compression of the sediment by an early-forming mineral phase, possibly pyrite, which was in turn replaced by kaolinite and then pyrophyllite at higher temperature and pressure. Woody structures such as cuticle and veins, which had resisted replacement by the initial low temperature phase, were coalified at higher temperatures.

Characteristics and controls of an offshore freshened groundwater system in the Shengsi region, East China Sea

Offshore freshened groundwater (OFG) has been encountered in continental margins around the world and identified as a potential unconventional water resource. In China, coastal areas and islands face limited freshwater resources. The East China Sea, specifically the region north of Shengsi islands, may contain an OFG system hosted in buried paleochannels associated with the ancient Yangtze river. To assess the OFG potential, characteristics, and controls in this region, we employed an integrated modeling approach. We constructed a 2D geological model of Quaternary sediments based on data from two well sites. By considering sea-level fluctuations over the past 200,000 years, we conducted a paleo-reconstruction of groundwater flow and solute transport conditions on the 2D transect. We compared the simulated present-day distribution of OFG in the model with borehole observations. Our findings indicate that the region was mostly sub-aerially exposed during the simulated period, allowing for potential meteoric recharge. Numerical results demonstrate a high likelihood of a laterally extensive OFG system existing today. The mechanism responsible for its formation appears to be meteoric recharge and offshore directed groundwater flow caused by increased hydraulic gradients during sea-level lowstand. The model suggests that the OFG system forms an oceanward dipping wedge, with the top occurring approximately 50–100 m below the seafloor. Freshwater is likely present down to the basement at around 250 m. The geometry and volume of the OFG system are strongly influenced by the shelf stratigraphy. We estimate the volume of freshwater in the region to range from 0.5 to 1.6 km3 km-1, indicating a viable potential freshwater resource for the Shengsi region and coastal city of Shanghai. To gain further insights, we recommend conducting additional investigations using geophysical techniques.

Deep Hydraulically‐Active Fractures in Sensitive Clay Deposits: Implications for Groundwater Flow and Slope Stability

AbstractLandslides in sensitive post‐glacial marine clays are one of the major geological hazards in Canada, Norway and Sweden. Current hydrogeological conceptual models used for slope stability analyses in these deposits consider simple groundwater flow conditions within a homogenous, isotropic, massive clay deposits, where fractures are surficial features that only exist within a 1–5 m‐thick weathered zone. This study uses cross‐correlation analysis on hydraulic head data from a large network of vibrating‐wire piezometers in clay deposits along the St. Lawrence River and in the Saguenay‐Lac St‐Jean Lowlands, in Quebec, Canada, to show that hydraulically‐active fractures are present to depths of up to 16 m at 4 (possibly 6) of the 7 locations studied. These findings suggest that current conceptual models have a high likelihood of misrepresenting local flow systems, and that further field and modeling work is needed to characterize the extent and influence of these fracture networks.

Modelling Interactions between Three Aquifer Thermal Energy Storage (ATES) Systems in Brussels (Belgium)

Shallow open-loop geothermal systems function by creating heat and cold reserves in an aquifer, via doublets of pumping and reinjection wells. Three adjacent buildings in the center of Brussels have adopted this type of aquifer thermal energy storage (ATES) system. Two of them exploit the same aquifer consisting of Cenozoic sands, and started operation in 2014 and 2017, respectively. A previous hydrogeological model developed by Bulté et al. (2021) has shown how the thermal imbalance of one of the systems jeopardizes the thermal state of this upper aquifer. Here, the interactions with a more recent third ATES system located in the deep aquifer of the Palaeozoic bedrock are studied and modelled. After being calibrated on groundwater flow conditions in both aquifers, a 3D hydrogeological model was used to simulate the cumulative effect of the three geothermal installations in the two exploited aquifers. The results of the simulations showed that although the hydraulic interactions between the two aquifers are very weak (as shown by the different observed potentiometric heads), heat exchanges occur between the two aquifers through the aquitard. Fortunately, these heat exchanges are not sufficient to have a significant impact on the efficiency of the individual geothermal systems. Additionally, this study shows clearly that adding a third system in the lower aquifer with a mean power of 286 kW for heating between October and March and an equivalent mean cooling power between April and September is efficient.

Arsenic mobilization in nZVI residue by Alkaliphilus sp. IMB: Comparison between static and flowing incubation

Arsenate reducing bacteria (AsRB) enhance arsenic (As) release via reducing As(V) to As(III), and As mobility is usually controlled by As(III) re-uptake on in-situ formed secondary iron minerals. The re-uptake of As(III) under groundwater flow conditions significantly impacts the fate and transport of As. Herein, a novel As(V)-reducing bacterium Alkaliphilus IMB was isolated in an As-contaminated soil. Scanning transmission X-ray microscopy showed that dissolved As(V) was mainly bound to the cell walls whereas dissolved As(III) was homogeneously distributed around IMB, indicating that As(V) reduction occurs outside the cell membrane. To explore the effect of IMB on As mobility, IMB was incubated with As-loaded nanoscale zero-valent iron (nZVI) residues under static and flowing conditions. IMB reduced 100% dissolved As(V) to As(III) even in a short contact time (∼1 h) during flowing incubation. The formation of As(III) did not influence As mobility under static condition as evidenced by the comparable concentrations of released As in the presence of IMB (8.5% to total As) and the abiotic control (10% to total As). Biogenic As(III) was re-adsorbed on the solids as shown by the higher ratio of solid-bound As(III) to total As in the presence of IMB (54%) than that in the abiotic control (12%). By contrast, the degree of As(III) re-adsorption was inhibited in the flowing environment, as suggested by the lower As(III) ratio in the solid (31%). This inhibition can be ascribed to the relatively slow adsorption of As(III) compared with the quick reduction of As(V) (∼1 h). Thus, IMB significantly enhanced As release during flowing incubation as shown that 9.8% As was released in the presence of IMB while 2.1% As in the abiotic control. This study found the contrary effect of AsRB on As mobility in static and flowing environments, highlighting the importance of re-adsorption rate of As(III).