Groundwater Flow Research Articles

Tracing metal sources and groundwater flow paths in the Upper Animas River watershed using rare earth elements and stable isotopes

Groundwater flow paths and processes that govern metal mobility and transport are difficult to characterize in mountainous bedrock watersheds. Despite the difficulty in holistic characterization, conceptual understanding of subsurface hydrologic and geochemical processes is key to developing remediation plans for locations affected by acid mine drainage, such as the Upper Animas River watershed in southwestern Colorado, USA. Stable isotopes of water and rare earth elements were utilized to evaluate groundwater flow and metal sources within this complex catchment. Stable isotope samples collected from draining mine adits and springs display systematic spatial variation wherein sample sites at higher elevations have greater seasonal variability than sites at lower elevations. The Upper Cement Creek watershed, where multiple draining mines are present, displays the lowest seasonal variation in stable isotopic signatures, potentially indicating the presence of a large, well-mixed volume of groundwater storage or interbasin groundwater flow. Rare earth elements display statistically significant variation between different alteration styles in the catchment. Overprinting of regional propylitic alteration is evident based on enrichment of middle rare earth elements in acidic springs and mines that are not spatially associated with surficial exposures of acid generating alteration styles. Europium anomaly and middle rare earth enrichment signatures from two flooded mine tunnels on opposite sides of a watershed divide indicate connections to the same subsurface flooded mine workings.

Coupled Effects of Fault-Related Groundwater Flow and Pore Water Pressure: Unraveling the Mechanisms of Deformation and Failure in Gentle Slopes

Coupled Effects of Fault-Related Groundwater Flow and Pore Water Pressure: Unraveling the Mechanisms of Deformation and Failure in Gentle Slopes

Controls on coastal saline groundwater across North America

Abstract Groundwater is crucial to sustaining coastal freshwater needs. About 32 million people in the coastal USA rely on groundwater as their primary water source. With rapidly growing coastal communities and increasing demands for fresh groundwater, understanding controls of continental-scale coastal groundwater salinity is critical. To investigate what hydrogeological factors (e.g., topography, hydraulic conductivity) control coastal saline groundwater at continental scales, we have simulated variable-density groundwater flow across North America with the newly developed Global Gradient-based Groundwater Model with variable Densities (G3M-D). The simulation results suggest that under a steady climate and pre-development conditions (i.e., steady 30-year mean groundwater recharge, no withdrawals nor sea level rise) saline groundwater is present in 18.6% of North America's coastal zone, defined as up to 100 km inland and up to 100 m above mean sea level. We find that the coastal zone is particularly vulnerable to containing saline groundwater at low hydraulic gradients (<10-4) and large hydraulic conductivities (>10-2 m day-1). To analyze model parameter sensitivities, i.e., which parameters control the resulting distribution of saline groundwater, we utilize the inherent spatial model variability. We find that hydraulic gradient, topographic gradient, hydraulic conductivity, and aquifer depth are important controls in different places. However, no factor controls coastal groundwater salinization alone, suggesting that parameter interactions are important. Using G³M-D based on G3M, a model that previous work found to be strongly controlled by topography, we find no controlling influence of recharge variability on the saline groundwater distribution in North America. Despite a likely overestimation of saline interface movement, the model required 492 000 years to reach a near-steady state, indicating that the saline groundwater distribution in North America has likely been evolving since before the end of the last ice age, approximately 20 000 years ago.

Rock strength and stress dependence of local flow-path connectivity within faults or fractures: a preliminary overview of virtual and in-situ hydraulic tests

Abstract Global flow path connectivity along faults or fractures depends on the degree of local flow path connectivity within each fault or fracture and is a key control of groundwater flow and solute transport. However, the mechanical controls on spatial variations in local flow path connectivity within individual faults or fractures are poorly understood. Local flow path connectivity is quantifiable by the laboratory-scale flow dimensions (n lab) within individual faults or fractures, with a lower n lab indicating lower local flow path connectivity. Virtual hydraulic tests were performed on modeled individual fractures to derive a relationship between n lab and a mappable indicator, the ductility index (DI), defined by the mean stress, groundwater pressure, and rock tensile strength. The derived relationship was verified with data obtained from in-situ hydraulic tests of natural faults in rocks with low matrix permeability, poor swelling capacity, and few fracture mineral fillings, also incorporating the effect of linkage among faults in the field. The test results demonstrated that local flow path connectivity within faults or fractures can be high (n lab > 1.5) when DI < 2 but is generally low (n lab < 1.5) when DI > 2, depending on the level of effective-normal-stress-dependent (DI-dependent) fracture-normal displacement. This relationship between n lab and DI is valid even when the value of DI is varied, or the faults are sheared. These findings can be used to help map spatial variations in local flow path connectivity within faults or fractures from limited borehole data.

The force of Forchheimer – the contributions of Philipp Forchheimer to groundwater hydrology

ABSTRACT Philipp Forchheimer must be considered one of the most important founding fathers of modern geohydrology. Connected to his name are the Forchheimer law, which describes non-Darcian flow in porous media, and the Dupuit-Forchheimer groundwater flow assumption. Probably unbeknownst to most current hydrologists, he introduced many more important concepts, which still are cornerstones of our field of study today. The most important is the Laplace equation, which forms the basis of all quantitative modelling of groundwater flow. Flow nets, the method of images and the refraction of flowpaths at layer boundaries are further concepts useful today. Through his work in several countries, many papers and textbooks on hydraulics, the latter translated into several languages, and, finally, his connection with the famous Vienna school of soil mechanics, he left a scientific legacy that is very much alive, although many are unaware that it goes back to Philipp Forchheimer.

Deciphering Groundwater-Surface water Interactions using Environmental Tracers in a Tropical Lake, Southwest India

This study focuses on identifying GW-SW interaction locations in a tropical lake - Vellayani Lake (VL), Southwest India, utilizing stable water isotopes (s18O, sD) and chloride mass balance approach. The northern lake region was identified as a critical groundwater discharge “hotspot” with pronounced discharge (2.14×106 - 3.82×106 m³/yr), prompting targeted management interventions. This reaffirms the critical role of groundwater inflow in sustaining the lake’s water balance. Additionally, the application of machine learning (ML) techniques refined the classification of Lacustrine Groundwater Discharge (LGD) and non-LGD sites while predictive modeling utilizing Sensitivity Indices enhanced the understanding of prominent factors influencing lake volume. K-means clustering and Random Forest (RF) classification, achieved high accuracy (90%) and a kappa value of 0.8 in distinguishing groundwater discharge and non-discharge sites. Predictive modeling and sensitivity analysis revealed precipitation as the most influential factor, with a ±20% change causing a 16.69% variation in lake volume. Groundwater discharge exhibited a sensitivity index of 0.5320, further emphasizing its critical role in maintaining lake hydrological balance. This integrated approach provided valuable insights into the critical role of nearshore groundwater recharge in maintaining lake hydrological balance and facilitates the identification of suitable areas for groundwater recharge structures. For practitioners and policymakers, this integrated approach offers a robust framework for identifying critical GW-SW interaction zones, prioritizing groundwater recharge areas, and designing sustainable water management strategies, especially in data-scarce regions, paving the way for improved resource management in similar tropical lake environments.

Interdependence Between River Aquifer Groundwater Flow and Temperature–Depth Profiles: Type Curves Based on Pi Theorem and Numerical Simulations

Interdependence Between River Aquifer Groundwater Flow and Temperature–Depth Profiles: Type Curves Based on Pi Theorem and Numerical Simulations

Modeling Groundwater Resources in Data-Scarce Regions for Sustainable Management: Methodologies and Limits

Groundwater modeling in data-scarce regions faces significant challenges due to the lack of comprehensive, high-quality data, impacting model accuracy. This systematic review of Scopus-indexed papers identifies various approaches to address these challenges, including coupled hydrological-groundwater models, machine learning techniques, distributed hydrological models, water balance models, 3D groundwater flow modeling, geostatistical techniques, remote sensing-based approaches, isotope-based methods, global model downscaling, and integrated modeling approaches. Each methodology offers unique advantages for groundwater assessment and management in data-poor environments, often combining multiple data sources and modeling techniques to overcome limitations. However, these approaches face common challenges related to data quality, scale transferability, and the representation of complex hydrogeological processes. This review emphasizes the importance of adapting methodologies to specific regional contexts and data availability. It underscores the value of combining multiple data sources and modeling techniques to provide robust estimates for sustainable groundwater management. The choice of method ultimately depends on the specific objectives, scale of the study, and available data in the region of interest. Future research should focus on improving the integration of diverse data sources, enhancing the representation of complex hydrogeological processes in simplified models, and developing robust uncertainty quantification methods tailored for data-scarce conditions.

Sources and Pathways of PFAS Occurrence in Water Sources: Relative Contribution of Land-Applied Biosolids in an Agricultural Dominated Watershed.

This study evaluated PFAS occurrence in rural well water and surface water relative to land application of biosolids in a tile-drained agriculture-dominated watershed. Spatial data were used to identify potentially vulnerable rural wells based on their proximity to biosolid-permitted land and location with respect to groundwater flow. Water was collected from 103 private wells in Greater Tippecanoe County Indiana and 168 surface water locations within the Region of the Great Bend of the Wabash River watershed. Overall, results indicate that surface water (∑PFAS ≤ 169.4 ng/L) is more vulnerable to PFAS contamination than well water (∑PFAS ≤ 15.7 ng/L). Short-chain perfluoroalkyl acids made up 72% of the ∑PFAS in both water sources. Nonetheless, long-chain homologues were detected more frequently in surface water (94%) than well water (82%). Hierarchical cluster analysis identified biosolid-applied fields, WTTPs, and industrial discharges as PFAS sources in first-order streams with high ∑PFAS. Temporal trends revealed an inverse relationship between streamflow and concentrations in surface water sites impacted by point discharges and vice versa for diffuse sources, thereby providing complementary evidence of potential sources. The well water data set did not show a distinct spatial trend between ∑PFAS and distance from biosolid application or well characteristics.

Radionuclide transport and retardation in uplifting granitic rocks: Part 2 – Modelling coupled processes in uplift scenarios

Uplifting fractured granitic rocks occur in substantial areas of countries such as Japan. Some of these areas might be considered when siting a deep geological repository for radioactive wastes. A repository site would be selected in such an area only if it is possible to make a safety case, accounting for the changing conditions during uplift. The safety case must include robust arguments that chemical processes in the rocks around the repository will contribute sufficiently to minimise radiological doses to biosphere receptors. Numerical modelling is an important aspect of making these arguments. To provide confidence in the safety arguments, numerical models need to be sufficiently realistic, but also parameterised conservatively (pessimistically). However, model development is challenging because uplift involves many complex couplings between groundwater flow, chemical reactions between water and rock, and changing rock properties. The couplings would affect radionuclide mobilisation and retardation, by influencing diffusive radionuclide fluxes between groundwater flowing in fractures and effectively immobile porewater in the rock matrix (rock matrix diffusion, RMD) and radionuclide partitioning between water and solid phases, via: (i) mineral precipitation/dissolution; (ii) mineral alteration; and (iii) sorption/desorption. It is difficult to represent all this complexity in numerical models while showing that they are parameterised conservatively. Here we present a modelling approach, illustrated by simulation cases for some exemplar radioelements, to identify realistically conservative process conceptualisations and model parameterisations.

Wetland vegetation zoning as a response to groundwater complex systems.

This research investigates the interplay between groundwater flow systems and the zoning of wetland species. We aimed to elucidate the relationship between these factors through comprehensive field evaluations encompassing plant composition, piezometric levels, and flow direction; groundwater chemistry, vertical and horizontal, at different depths (0.15m, 2m, 4m, and 6m) during both rainy and dry seasons. Our findings reveal distinct patterns. The plant diversity in the FP site was related to low ion concentration. In contrast, the dominance of T. geniculata in the TH site correlated with species adapted to sulfate and chloride (SO42- and Cl-) tolerance. In the CTC site, the dominance of C. jamaicense was linked to local groundwater flow and significant surface water inflows. At the same time, T. domingensis prevailed in the TC site due to sodium chloride facie inhibiting C. jamaicense seed germination. Our study highlights the role of groundwater chemical composition in shaping wetland ecosystems by influencing species tolerance and how the spatial distribution of groundwater discharge and seasonal changes contribute to distinct vegetation patches within wetlands. The relationship between groundwater systems, the water's chemical composition, and vegetation is strongly dependent. This can explain mortality and changes in vegetation composition in wetlands in different parts of the world, stressed by climate change effects (rain pattern alteration).

Socioeconomic and Environmental Impacts of Eucalyptus Plantations in Ethiopia: An Evaluation of Benefits, Challenges, and Sustainable Practices

Eucalyptus was first introduced to Ethiopia in the late 19th century to address the scarcity of firewood and construction wood in the capital city. Since then, it has spread across the country and has become an important source of income for many households while also reducing the need for deforestation. Despite concerns raised by environmentalists about its eco‐hydrological impact, the plantation has expanded to cover a vast area of the nation, including farmlands and mountainous regions. Currently, around 506,000 hectares of land in Ethiopia are covered by Eucalyptus plantations. The growth of Eucalyptus plantations can be attributed to various socioeconomic, ecological, and biological factors, including the increasing demand for wood and wood products. However, this growth has also led to negative environmental consequences such as reduced surface and groundwater flow, decreased crop productivity, soil fertility degradation and depletion, and high water consumption, which can result in water scarcity. To address these environmental impacts, it is essential to select appropriate species and sites and implement proper silvicultural and land use planning before planting. Additionally, promoting renewable energy sources and planting environmentally sound fast‐growing indigenous and exotic tree species can help reduce the adverse effects of Eucalyptus on the environment.

Groundwater Flow under Irrigation Canals Lied on Inclined Cut-off Walls with Different Angles

Groundwater Flow under Irrigation Canals Lied on Inclined Cut-off Walls with Different Angles

Corrigendum to “Investigating Steady Unconfined Groundwater Flow using Physics Informed Neural Networks” [Advances in Water Resources Volume 177 (2023), 104445

Corrigendum to “Investigating Steady Unconfined Groundwater Flow using Physics Informed Neural Networks” [Advances in Water Resources Volume 177 (2023), 104445

Occurrence and enrichment mechanisms of groundwater hexavalent chromium in typical loess area of China.

Understanding the geochemical mechanisms governing hexavalent chromium (Cr(VI)) in groundwater is essential for mitigating health risks. However, the processes driving Cr(VI) accumulation and migration in loess regions remain insufficiently understood. This study investigated the occurrence, release, and migration mechanisms of Cr(VI) across different groundwater environmental units (GEUs) in the south-central Loess Plateau, China. This study used combined approach of isotopic analysis, multivariate statistical methods, hydrochemical graphical methods, and GIS technology to reveal the origins and processes influencing Cr(VI) hydrogeochemistry within these GEUs. The results revealed significant spatial variability in Cr(VI) concentrations among the GEUs, ranging from below the detection limit to 300μg/L, with nearly 40% of samples exceeding the WHO limit. Pronounced enrichment of Cr(VI) was observed in the fissure-pore water of the loess tableland and pore water of the alluvial plain. Cr(VI) enrichment and release in the GEUs were facilitated by oxidative conditions (high Eh, SO42-/HCO3-, Mn-oxide presence) and cation exchange processes under slightly alkaline conditions (pH>7.80). Key hydrogeological processes and geomorphological factors, including lateral runoff recharge, slow groundwater flow in the loess tableland, vertical recharge, extensive water-rock interactions, and hydraulic gradients were identified as critical divers of Cr(VI) migration and enrichment across different GEUs. Under reductive conditions, Cr(VI) was reduced to Cr(III), particularly in the pore water of the alluvial plain, but competitive adsorption with nitrate allows the enrichment of Cr(VI) in groundwater, particularly in the fissure-pore aquifer. A conceptual model was developed to elucidate Cr(VI) sources and migration mechanisms in groundwater, offering a framework for risk mitigation and management of groundwater in loess regions.

Ensemble modeling of the two-dimensional stochastic confined groundwater flow through the evolution of the hydraulic head’s probability density function

Ensemble modeling of the two-dimensional stochastic confined groundwater flow through the evolution of the hydraulic head’s probability density function

Unsteady flow analysis in a double-suction pump as turbine impeller based on finite-time Lyapunov exponent

Pump as turbine (PAT) is an excellent energy recovery device. Understanding the flow characteristics of the key component, the impeller, is essential for further optimization and design of PAT. To analyze the unsteady flow characteristics inside the impeller of a double-suction PAT from a Lagrangian perspective, numerical simulations were conducted using the shear stress transport k–ω turbulence model for the design conditions. The finite-time Lyapunov exponent (FTLE) method was employed to extract the two-dimensional and three-dimensional Lagrangian coherent structures (LCSs) of the impeller over one cycle of unsteady velocity field. Results indicate that with time, the scale of the FTLE field gradually decreases, suggesting enhanced flow stability, reduced mixing efficiency, smoother flow structures, and increased flow convergence. In the two-dimensional perspective, high FTLE values concentrate at the inlet region of the passage, pressure side of the blades, and outlet region of the passage, spreading gradually over the entire blade surface, while low FTLE values predominantly concentrate on the blade surface with a diminishing area. The flow separation occurs at the leading edge of the impeller, the suction side of the impeller and the inlet region of the flow channel. In the three-dimensional perspective, different LCSs show varied changes at specific FTLE values, reflecting the impact of FTLE variation on the distribution of LCSs and indicating the evolution of flow states in fluid dynamics. Each moment of LCS exhibits a growth–stability–dissipation status transition. The FTLE method effectively reveals the flow variations inside the impeller of a double-suction PAT, offering a new perspective and tool for analyzing the turbulent structures in the complex flow field of PAT.

Groundwater Quality Assessment and Modeling Using Water Quality Index and Mathematical Models: Case Study of Bam Province, Burkina Faso

In light of groundwater's fundamental role in providing drinking water to populations in the Sahel, its management and monitoring are vital for predicting and mitigating future crises. The goal of this study is to assess the groundwater quality in Bam province using the Water Quality Index (WQI), and to predict these indices through the application of Artificial Neural Networks (ANN) and traditional Multiple Linear Regression (MLR) techniques. In this context, a variety of physicochemical parameters such as Total Hardness (TH), pH, Electrical Conductivity (EC), calcium, magnesium, sodium, potassium, ammonium, bicarbonate, chloride, sulphate, nitrite, nitrate, phosphorus, and fluoride were collected from 154 boreholes, analysed, and used to calculate the WQIs. These parameters were employed as inputs, while the WQIs served as the output target for the models. The data were arranged in ascending order based on the indices, with 70% of the data reserved for training the models and 30% for testing. The groundwater quality in the study area, characterized by its geological heterogeneity and discontinuous fractures affecting groundwater flow, is predominantly excellent, with 95.45% of the samples having WQIs below 50. The remaining 4.55% is split between good (3.90%) and poor (0.65%) quality, with WQIs ranging from 50–100 and 100–200, respectively. In terms of predictive modeling, the ANN method provided the most accurate results, with R² (coefficient of correlation) = 0.99, RMSE (Root Mean Scare Error) = 0.0037, and MAE (Mean Absolute Error) = 0.0032 for the training set, and R² = 0.96, RMSE = 4.46, and MAE = 3.27 for the testing set. By comparison, the traditional method showed lower accuracy with R² = 0.61, RMSE = 2.71, MAE = 2.02 for the training set, and R² = 0.93, RMSE = 7.97, MAE = 6.32 for the testing set. The slight decrease in model accuracy during the testing phase is attributed to the challenge of modeling strong indices with weaker ones, as well as the geological heterogeneity and discontinuities that complicate groundwater quality prediction. However, this does not affect the model’s ability to predict extreme situations, such as water pollution events.

Study on numerical simulation of groundwater flow field and slope stability in multi-aquifer open pit mine

Water is one of the most important influences on slope stability in open pit mines. In order to solve the problem of slope stability analysis in multi-aquifer open pit mines, the open pit mine in Block I of Thar Coalfield in Pakistan with multiple aquifers was taken as the research background. The groundwater flow field at different excavation phases was analyzed by numerical simulation method. Based on the seepage theory of groundwater, the distribution law of hydrostatic pressure in phreatic aquifer and confined aquifer was analyzed. Based on the rigid body limit equilibrium method, the slope stability analysis method under the action of hydrostatic pressure of multiple aquifers was proposed. Based on the water level distribution within the slope body obtained by numerical simulation, the slope stability at different excavation phases was calculated, and the influence of aquifers on slope stability was analysed. The research results show that: With the excavation and drainage of the mine pit, the groundwater flow field in the open pit mining area changes significantly, and a descending funnel was formed at the mine pit. When mining reached the pit bottom boundary, the water level dropped by about 155–163 m in the mining area. The hydrostatic pressure action of aquifer on slope is related to water level, quantity and location of aquifer. Under the condition of considering hydrostatic pressure of aquifer, the slope stability coefficients are all reduced. And the slope stability coefficients of the three different mining phases were reduced by 6.74%, 11.87%, and 5%, respectively. The more aquifers the sliding surface crosses, the greater the effect of hydrostatic pressure on slope stability. When mining to the boundary, the combined sliding surface passed through two aquifers, and the slope stability coefficient decreased by 5% under the hydrostatic pressure condition, and the arc sliding surface passed through three aquifers, and the slope stability coefficient decreased by 8.74% under the hydrostatic pressure condition. The stability of slope with arc sliding mode is more affected by aquifer hydrostatic pressure than that with combined sliding mode. When mining to the floor of the coal seam roof confined aquifer, the stability coefficient of slope with combined sliding surface decreased by 11.87%, while that with arc sliding mode decreased by 16.32%.

Predictive simulation of groundwater contamination due to landfill leachate: A case study on the Robinson Deep Landfill, Johannesburg, South Africa

Groundwater contamination from municipal solid waste landfills is a global issue, including South Africa. The Robinson Deep landfill (RDL) in Johannesburg lacks necessary leachate collection and handling facilities, has a shallow groundwater table, and no groundwater quality forecast tool. This situation poses a risk of groundwater contamination. This study aimed to construct groundwater flow and contaminant transport models to predict contamination from leachate migration at RDL. Visual MODFLOW Flex software was used for model construction and verification. Heavy metal concentration observations (Al, Cd, Mn, and Pb) from boreholes BH-1, BH-2, BH-3, and BH-H near the RDL were used to calibrate and validate the contaminant transport model (CTM). The result of the CTM predictive simulations for 2030 show Mn and Pb concentrations in the BH-H groundwater could reach 4.28 mg/L and 6.85 mg/L, respectively, exceeding permissible limits of 0.01 mg/L for Pb and 0.4 mg/L for Mn. The simulations indicate that the RDL threatens groundwater quality, especially in the northern areas of the landfill. Based on these findings, a recommendation is made for future studies on assessment and modelling of groundwater quality to focus on areas where increased concentrations of Pb and Mn are predicted. Further, it is recommended that precautionary preventive measures be implemented to mitigate possible contamination of groundwater in the northern areas of the landfill.