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Understanding how groundwater level changes affect the permeability of bedrock aquifer‐aquitard systems is important for groundwater management, yet this relationship remains poorly understood. This study focuses on Tangshan in the northeastern North China Plain, utilizing tidal response analysis to investigate the dynamic interplay between groundwater level trends and permeability variations in bedrock aquifer‐aquitard systems. High‐frequency groundwater level data from two monitoring wells were employed to reveal a significant positive correlation: rising groundwater head leads to increased permeability of the bedrock aquifer‐aquitard system, primarily due to adjustments in groundwater head. This research provides direct evidence that both climate variability and human activities can influence bedrock aquifer‐aquitard permeability through changes in the groundwater head. The findings highlight the importance of integrating models of dynamic permeability induced by hydrological processes into groundwater resource management frameworks and hazard assessments, particularly in regions experiencing groundwater level recovery, such as the North China Plain.

Existing groundwater flow models for leaky aquifer systems rarely consider the consolidation effects of aquitards. Neglecting these effects can significantly impact the accuracy of groundwater flow simulations within such systems. To address this issue, this paper develops a model that describes unsteady flow within a leaky aquifer system incorporating nonlinear consolidation. The flow in both unconfined and confined aquifers is radial one‐dimensional Darcian flow, whereas the flow in the aquitard is vertical one‐dimensional non‐Darcian flow, considering nonlinear consolidation. The finite difference method is used to solve the model, and the difference between the results obtained with and without considering consolidation effects is examined. The findings indicate that the groundwater head in the confined aquifer, when considering the effects of consolidation, is higher than that in the confined aquifer without consolidation effects. Initially, this difference in confined groundwater head increases rapidly with time, and then progressively decreases. The magnitude of this difference is positively correlated with the aquitard's compressibility index and permeability index, as well as with the pumping rate. Conversely, it is negatively correlated with the aquitard's threshold hydraulic gradient and initial void ratio, the confined aquifer's hydraulic conductivity and specific storage, and the unconfined aquifer's hydraulic conductivity and specific yield. During the early period of pumping, the difference is positively correlated with the aquitard's initial vertical hydraulic conductivity; however, this correlation reverses in the late period of pumping. Finally, a case study is employed to validate the effectiveness of the developed model. Key Points We develop a model that describes low‐velocity non‐Darcian flow with nonlinear consolidation in a leaky aquifer system Characteristics of aquitard consolidation influenced by nonlinear consolidation and low‐velocity non‐Darcian flow are investigated The influences of various factors on the differences in results, with and without considering consolidation effects, are analyzed

The ambitious agricultural development projects in Egypt and the associated horizontal expansion into the core desert lands and desert fringe zones around the Nile Valley primarily depend on water availability. This study investigates the vertical recharge from the deep Nubian Aquifer System (NAS) toward the shallow aquifers, including the Carbonate and Quaternary aquifers in southern Egypt. While this connectivity has been studied locally through case studies, the present study integrates stable isotope data from all previous studies, together with analyses from vastly distributed new groundwater samples, remote sensing, and geophysical methods to better understand groundwater dynamics and aquifer connectivity over a regional domain. Findings show that: (1) the depths to the basement surface range from 350 to 4700 m below the land surface, (2) the major structural trends are E-W, NW–SE, NE-SW, ENE, NNW, and WNW trends, (3) the contribution ratios from the deep NAS to the overlying aquifers range between 10 and 98% as estimated using isotope mass balance calculations, and (4) the intersection of NW, ENE, and NE structural trends, which show similar trends between surface faults and deep faults, indicating vertical continuity, plays a major role in aquifer connectivity along the western desert fringes of the Nile River, particularly south of latitude 26°30′N. These findings indicate that the relatively thin sedimentary cover overlying the NAS south of latitude 26°30′N facilitates the upwelling of the NAS groundwater along with the intersection of the NW, ENE, and NE fault systems. Given the consensus of high hydraulic heads of the NAS compared to the overlying aquifers, the study suggests that a large-scale vertical upwelling at the deduced intersecting structural trends throughout the entire Limestone Plateau is worthy of further investigation. Such vertical upwelling could bring significant groundwater resources to shallow levels, as long as the NAS maintains its higher heads, and thus supports desert greening projects in Egypt. The findings also highlight the necessity of examining similar mechanisms in other desert environments with multiple aquifer systems.

This paper discusses the geological and hydrogeological features of Quaternary deposits in Tianjin as well as the geohazards related to groundwater hydrology in this region. The soft soil deposits, comprising silt, sand, silty clay and clay, are composed of four aquifer groups. In the first aquifer group, one phreatic aquifer and two confined aquifers have relationships with underground construction in the urban area. These three aquifers are separated by two aquitards and collectively form a multi-aquifer system. During geotechnical construction, potential geohazards present are related to the groundwater, which include water-in-rushing, quicksand and piping hazards. To prevent the aforementioned geohazards, dewatering is conducted; however, groundwater pumping may result in large settlements of the surrounding ground. To reduce pumping-induced settlement, the dewatering–waterproofing system has been adopted. According to the characteristics of the subsoil, excavation depth and the surrounding environment, the dewatering system can be divided into five patterns. In the first four patterns, when pumping is conducted in the excavation pit, the groundwater head in the adjacent aquifers outside the pit decreases due to the leakage effect of the aquitards located between the aquifers. In the fifth pattern, waterproof curtain has cut off the aquifers completely and dewatering in the pit cannot result in settlement around excavation pit. To avoid geohazards related to groundwater hydrology, countermeasures recommended include construction of an effective waterproof curtain, selection of a reasonable excavation dewatering pattern and withdrawal of required groundwater.

An integrated hydro-geophysical and hydrochemical investigation was conducted to delineate aquifer geometry, assess groundwater potential, and evaluate water quality in the southern part of Wadi Qena, Eastern Desert, Egypt. Eighteen time-domain electromagnetic (TDEM) soundings, ground magnetic profiles, pumping-test data, and six groundwater chemical analyses were jointly interpreted. The integrated datasets reveal five geo-electrical layers and identify two main aquifer systems: a shallow Quaternary aquifer (50–300 m depth; 4.9–86 Ω m) and a deeper Nubian Sandstone aquifer (300–650 m depth; 4.7–17.6 Ω m). Magnetic modeling delineates a variable basement surface (350–850 m) that controls aquifer thickness and the spatial distribution of transmissive zones. Areas of deep basement lows coincide with high-transmissivity wells (655–1170 m 2 /day) and low resistivity, indicating thick, well-connected sandstone bodies. Hydrochemical data (TDS: 1447–1607 mg/L; Na–Cl facies) indicate increasing salinity toward the northwest, consistent with upward leakage along magnetic lineaments and the dissolution of salt-bearing formations. The integrated interpretation demonstrates that combining TDEM, magnetic, and geochemical approaches provides a robust framework for identifying productive aquifers, understanding salinity sources, and optimizing groundwater development in arid terrains.

The extraction of groundwater can generate land subsidence by causing the compaction of susceptible aquifer systems, typically unconsolidated alluvial or basin-fill aquifer systems comprising aquifers and aquitards. Various ground-based and remotely sensed methods are used to measure and map subsidence. Many areas of subsidence caused by groundwater pumping have been identified and monitored, and corrective measures to slow or halt subsidence have been devised. Two principal means are used to mitigate subsidence caused by groundwater withdrawal—reduction of groundwater withdrawal, and artificial recharge. Analysis and simulation of aquifer-system compaction follow from the basic relations between head, stress, compressibility, and groundwater flow and are addressed primarily using two approaches—one based on conventional groundwater flow theory and one based on linear poroelasticity theory. Research and development to improve the assessment and analysis of aquifer-system compaction, the accompanying subsidence and potential ground ruptures are needed in the topic areas of the hydromechanical behavior of aquitards, the role of horizontal deformation, the application of differential synthetic aperture radar interferometry, and the regional-scale simulation of coupled groundwater flow and aquifer-system deformation to support resource management and hazard mitigation measures.

A series of hydrogeologic framework model (HFM)‐based steady‐ and transient‐state numerical simulations is performed first using a coupled subsurface flow‐transport numerical model to analyze groundwater flow and salt transport in an actual three‐dimensional complex coastal aquifer system before and during groundwater pumping. A series of analytic hierarchy process (AHP)‐based multi‐criteria evaluations is then performed applying a multi‐criteria decision‐making approach to determine optimal pumping location and rate for a new pumping well in the complex coastal aquifer system during groundwater pumping. The complex coastal aquifer system is composed of six anisotropic fractured porous geologic media (five rock formations and one fault) and three isotropic porous geologic media (three soil formations) and shows high geometric irregularity and significant heterogeneity and anisotropy of the nine geologic media. Results of the steady‐state numerical simulations show successful model calibration with 26 measured groundwater levels and two observed seawater intrusion front lines. The latter two are determined by spatial interpolation and extrapolation of electrical conductivity logging data and electrical resistivity survey data, respectively. Based on the status and prospect of necessary water uses and available groundwater resources, the field observations of groundwater and seawater intrusion, and the analyses of the steady‐state numerical simulation after the model calibration, six candidate pumping locations are selected for the new pumping well. In addition, from six preliminary individual transient‐state numerical simulations, maximum pumping rates at the six candidate pumping locations are calculated first, and a set of six incremental candidate pumping rates is then assigned at each of the six candidate pumping locations. Results of the transients‐state numerical simulations show that groundwater flow and salt transport are spatially and temporally changed, and seawater intrusion is further intensified by groundwater pumping. In addition, the magnitudes of such spatial and temporal changes and intensification are significantly different depending on the candidate pumping locations and rates. Results of the steady‐ and transient‐state numerical simulations also show that both complexity (geometric irregularity, heterogeneity, and anisotropy including the fault) and topography have significant effects on the spatial distributions and temporal changes of groundwater flow and salt transport in the coastal aquifer system before and during groundwater pumping. In addition, results of statistical estimations of the mesh Peclet and Courant numbers confirm acceptabilities of minimizing numerical dispersion in the steady‐ and transient‐state numerical simulations. Based on the analyses of the transient‐state numerical simulations, eight multiple criteria are chosen to judge, prioritize, and rank the six candidate pumping locations and six candidate pumping rates for optimal pumping. Results of the multi‐criteria evaluations determine the optimal pumping location and rate for the new pumping well among the six candidate pumping locations and six candidate pumping rates. In addition, results of consistency checks confirm consistencies of judgments in the multi‐criteria evaluations. Key Points Numerical simulations with successful model calibration show that spatial and temporal changes in groundwater flow and salt transport significantly depend on candidate pumping locations and rates Statistical estimations of the mesh Peclet and Courant numbers confirm acceptabilities of minimizing numerical dispersion in the numerical simulations Multi‐criteria evaluations determine optimal pumping location and rate, and consistency checks confirm consistencies of judgments in the multi‐criteria evaluations

The Kingdom of Saudi Arabia is facing challenges related to water scarcity, however, the Cambrian-Ordovician Saq Aquifer System, in Al Qassim Province, provides vital water resources. This article assesses the petrophysical properties and hydrochemical characteristics of the aquifer system utilizing downhole cam recording and geostatistical analysis. The evaluation aims to assign the hydrogeological attributes, groundwater potential, and associated risks using an open-petrophysical aquifer system approach. The petrophysical evaluation appraises the prevailing lithology, zonation, hydrogeological properties, and salinity patterns. Sandstones with low shale content and dispersed distribution possess effective porosity that is fully saturated with groundwater containing calcium and bicarbonate ions. The majority of groundwater samples exhibit simple dissolution or lack prevailing ionic concentrations, indicating an ancient marine water genesis and a fossilized water type. The resistivity-depth profiles reveals three potential water-bearing aquifers including a disconnected compartment of an unconfined aquifer, a continuous compartment of a confined aquifer, and a continuous compartment of an unconfined aquifer. Petrophysical and hydrochemical parameters have been analyzed using geostatistical methods to assess their spatial variability and reduce potential sampling errors. Three distinct risk segments (RSs) with varying levels of risk characterize the aquifer system. RS-A represents a potential aquifer with low risk, RS-B poses moderate risks, and RS-C carries high risks. A fairway map of the aquifer system assigns geologic-hydro related factors that influence aquifer assessment and risk mapping. Segment-A is deemed an attractive long-term investment opportunity with low risk, while Segment-B offers a good investment opportunity with moderate risk. Segment-C provides a fair investment opportunity but entails high risks related to petrophysical qualities, hydrochemical characterizations, and irrigation utilities. The extraction and utilization of groundwater present promising investment opportunities, while employing a petrophysical approach can effectively evaluate and manage groundwater resources for sustainable utilization.

Coastal groundwater dynamics and solute transport were influenced by multiple factors including aquitards, tides, evaporation, and slope breaks in coastal aquifers. However, quantification of the impacts of these factors on groundwater flow and salinity distribution remains a challenge. In this study, both field observations and numerical modeling were applied to investigate hydraulic heads and groundwater salinity in a tidal flat with large‐scale seepage faces at Laizhou Bay, China. Results showed that seepage‐face evaporation increased groundwater salinity landward and promoted groundwater and salt exchange within the intertidal zone significantly in comparison to the case without evaporation. Seawater infiltrated the aquifer on the left of the slope break and discharged on the right, forming a groundwater circulation cell, which notably influenced leakage flow between unconfined and confined aquifers through the aquitard. The aquitard prevented approximately 85% of inland freshwater discharge near the slope break, resulting in the formation of two atypical freshwater discharge tubes in the upper and middle intertidal zones. Two additional groundwater circulation cells developed in the lower intertidal zone due to the spring‐neap tidal cycle. The outflow and inflow fluxes over a spring‐neap tidal cycle were numerically estimated to be 1.46 and 1.27 m2/d, respectively, with evaporation accounting for 45% of the outflow flux. These findings provide significant insights for further investigations on groundwater dynamics and solute transport in multi‐layered coastal aquifers, and have strong implications for biogeochemical processes within the intertidal zone. Plain Language Summary The coastal aquifer serves as a crucial connection between terrestrial and marine systems, with groundwater flow and salt transport in coastal regions influenced by factors such as topographic variations (e.g., slope break), tides, aquitards (low‐permeability layers among permeable layers), and evaporation. Quantification of these complex processes is a challenge. Here, we combined field observations and numerical simulations to quantify the effects of slope break, tides, aquitard, and evaporation on groundwater flow paths and salinity distribution beneath a tidal flat. It was found that evaporation may significantly increase groundwater salinity landward, and promoted the mass exchange between groundwater and seawater on the tidal flat surface. The combined effects of slope break, spring‐neap tidal cycle, and aquitard notably altered the pathways of groundwater flow and solute transport in coastal aquifers. These may profoundly influence the biogeochemical conditions in multi‐layered coastal aquifers, with important implications for coastal management and environmental protection. Key Points Seepage‐face evaporation significantly increases groundwater salinity and promotes groundwater/salt exchange within the intertidal zone Two new freshwater discharge tubes and three groundwater circulation cells develop due to the aquitard, spring‐neap tidal cycle, slope break Significant exchanges of groundwater and solutes occur between unconfined and confined aquifers via leakage under the slope break

The Cunene Province (Southern Angola) is facing recurrent and pluriannual droughts. Surface water supply could be reinforced using the groundwater resources of the multilayered aquifer systems (MAS) hosted in the siliciclastic sediments of the Kalahari Group. The MAS were first identified in the early 2000s in Northern Namibia and recently in the Cunene Province, by studies of the PLANAGEO project based on modern processing and reinterpretation of legacy data from the 1960s and 1970s (electrical resistivity data and deep boreholes). This article presents the results of a time domain electromagnetic (TDEM) survey conducted in the Cunene Province to: (i) contribute to the design of the hydrogeological conceptual model of the transboundary MAS, namely their geometry and extension; (ii) validate the reprocessing of the legacy data; and (iii) guide the future location of boreholes. Results depict the geometry of the sedimentary basin and the characterization of the MAS, with particular emphasis on the intermediate and deep aquifers. The borehole siting, based on the interpretation of the new TDEM data and the legacy data (clay markers in borehole logs), was successful, with a good agreement between estimated and observed horizons of the deep aquifers. However, the presence of clayey layers, a clay-rich matrix in the detrital deposits and saline/brackish groundwater led to uncertainties in the interpretation of the electrical transects. As such, recommendations are made to improve future data collection and mapping of the MAS.