Search Results (115)

Reliable estimates of aquifer properties are needed for groundwater resources management and for engineering applications. Pumping tests conducted in fractured aquifers using an open borehole may not produce a proper characterization of the aquifer properties leading to the failure of engineering solutions. In this work, we apply a radial flow model to reproduce the time drawdown curves recorded at an observation borehole instrumented with multi-level piezometers drilled in the Permo-Triassic sandstone, which is a complex fractured hydraulic unit. The radial flow model and the optimization code PEST are used to estimate the aquifer hydraulic parameter values. The model is then used to investigate the implications of replacing the multi-level piezometers with an open borehole. The results show that the open borehole does not only significantly alter the groundwater head and flow patterns around the borehole, but the analysis of the time drawdown curve obtained would produce estimates of aquifer properties that bear no relationship with the actual hydraulic properties of the aquifer. For engineering control studies, the pumping test must be carefully designed to account for the presence of fractures, and these must be represented in the analysis tools to ensure the correct characterization of the hydraulic system. Full article

Foundation pit pumping induces groundwater drawdown both inside and outside the pit, consequently causing surrounding land subsidence. Based on actual engineering cases, this study established a three-dimensional numerical model using ABAQUS software (version 6.14-4) to systematically investigate the temporal evolution of groundwater drawdown and land subsidence during pit pumping, while quantifying the relationship between drawdown and subsidence stabilization time under different parameters. The key findings are as follows: (1) land subsidence stabilization time (50 days) is governed by external phreatic layer response, reaching 2.3 times longer than isolated aquifer conditions (22 days); (2) medium-permeability strata (0.01–10 K_0,AdII) showed peak sensitivity to drawdown–subsidence coupling; (3) pumping from a confined aquifer extends the subsidence stabilization time by a factor of 1.1 compared to phreatic aquifer conditions. These findings provide valuable insights for the design and risk assessment of dewatering strategies in foundation pits within multi-aquifer systems. Full article

Hydraulic tomography (HT) based on the successive linear estimator (SLE) offers the high-resolution characterization of aquifer heterogeneity but conventionally requires prolonged pumping to achieve steady-state conditions, limiting its applicability in contamination-sensitive or low-permeability settings. This study bridged theoretical and practical gaps (1) by identifying spatial periodicity (hole effect) as the mechanism underlying divergences in steady-state cross-correlation patterns between random finite element method (RFEM) and first-order analysis, modeled via an oscillatory covariance function, and (2) by validating a novel short-term sampling strategy for SLE-based HT using field experiments at the University of Göttingen test site. Utilizing early-time drawdown data, we reconstructed spatially congruent distributions of hydraulic conductivity, specific storage, and hydraulic diffusivity after rigorous wavelet denoising. The results demonstrate that the short-term sampling strategy achieves accuracy comparable to that of long-term sampling strategy in characterizing aquifer heterogeneity. Critically, by decoupling SLE from steady-state requirements, this approach minimizes groundwater disturbance and time costs, expanding HT’s feasibility to challenging environments. Full article

Managing groundwater flow in crystalline basement aquifers (CBAs) remains challenging due to their dependence on secondary permeability fields characterized by high spatial variability. This study combines pumping and tracer tests to estimate the hydraulic properties and connectivity in four bedrock wells within a CBA in Southwestern Nigeria. The pumping tests caused drawdowns up to 4.13 m and 12.60 m in observation and pumping wells, with significant drawdowns only in three of four wells, revealing poor connection with the fourth well. The time-drawdown plots confirm double porosity effects suggesting fracture and matrix flow and release of water from a fractured dyke. Fracture and matrix hydraulic conductivities exceeded 7.9 × 10⁻⁷ m/s and 1.00 × 10⁻¹⁰ m/s, while the aquifer yield ranged from 0.08 to 0.34%. Groundwater flow velocity and dispersivity of 5.80 × 10⁻⁴ m/s and 2.60 m were estimated from the tracer test, while a Peclet number of 3.25 suggests dominant advective flow. Calculated sustainable yield shows that each well could provide water for up to 1600 people under controlled low pumping at 0.50 l/s with higher rates possible using larger diameter wells. These results confirm high variability in groundwater flow within CBAs, justifying the need to characterize them effectively. Full article

In water-rich strata, a traditional vertical barrier exhibits certain limitations when applied to deep foundation pit construction under complex geological conditions, such as it is difficult to completely cut off deep and thick aquifer, which may pose potential risks during pit dewatering. To address the above challenge, this study introduced a mixed barrier system in which the horizontal barrier (HB) was set at the bottom of the foundation pit and was combined with the enclosure wall to collectively retard groundwater seepage into the pit. Based on an actual project in Tianjin, this study established HB models with varying numbers of its layers using ABAQUS 6.14 software. It systematically investigated the effect of HB on groundwater drawdown, ground surface settlement, and enclosure deflection during foundation pit dewatering. The research shows that HB can significantly reduce the magnitude of external water level drawdown by altering groundwater seepage paths while effectively controlling soil settlement. Furthermore, it exhibits favorable overall restraining effects on wall deformation. Varying the number of horizontal barrier layers (L) exhibits an insignificant effect on water-blocking and subsidence-control performance. However, the constraint effect on the enclosure shows a correlation with L. Full article

A more precise definition of groundwater dynamics is an urgent issue for developing reliable plans to assist in the sustainable management of these resources. The combination of remote sensing input data with groundwater flow models emerges as a tool capable of representing these dynamics and simulating important conditions for developing adequate groundwater exploitation plans. These technologies allow for a more detailed and accurate analysis of the interactions between the factors influencing aquifers’ behavior, such as climate variability and anthropogenic pressure on water resources. Thus, the present study aims to develop a numerical model of groundwater flow in the aquifers of the Recife Metropolitan Region, state of Pernambuco, in Brazil, to evaluate the dynamics of these waters and the piezometric level drawdowns between 2004 and 2023. The FREEWAT platform, which applies the MODFLOW-2005 code, was used to simulate the study area. The results showed the entry of seawater into some formations and drawdowns that reached more than 100 m at some points, indicating the urgent need for management strategies to mitigate salinization and preserve the quality of the region’s groundwater resources. Full article

Groundwater resources are becoming increasingly scarce, especially in arid regions of western Kazakhstan. By 2070, the domestic and drinking water demands will increase from 640 to 901 thousand m³/day. This deficiency may be overcome by utilizing the Zhem Artesian Basin’s Cretaceous Albian–Cenomanian aquifer complex. The hydrodynamic interactions between the 123 known aquifer segments and recharge zones of these promising, exploitable, high-quality groundwater sources are unclear. While MODFLOW is a nominal platform for groundwater flow assessment, which is usually used for the simulation of simple hydrological scenarios, in this study, integrating several different scales and functional modules over a GIS platform enabled delineation and the forecast of this multi-layer aquifer complex. The MODFLOW simulation assessed exploitable groundwater resources and reservoir interactions, enabling the establishment of a simultaneous operation to the Zhem aquifer complex and its neighboring reservoirs. The model suggests that the total exploitable groundwater resources may grow to 629.4 thousand m³/day during the next 50 years. The simultaneous drawdown model suggests a water level decrease of up to 80 m at the end of this period, which will cause a river flow reduction of approximately 6% of the average long-term river flow. Thus, the assessed exploitable groundwater resources will cover more than 70% of the future regional water demand. The mathematical model developed may be used for monitoring and forecasting groundwater head and water balance changes and may be applied to attain a more detailed groundwater resource transfer scheme with economic criteria. Full article

Groundwater levels were monitored before, during and after groundwater pumping to understand the impacts of groundwater extraction on Abercorn Spring, a recharge spring in the Great Artesian Basin (GAB) in southeast Queensland, Australia. We measured the wetted area of the spring during this time to understand if changes in hydrology affected the water available for vegetation communities. Sustained groundwater extraction >20 km upgradient of the spring resulted in (1) rapid drawdown of the source aquifer, causing a reduction in aquifer pressure; (2) a small decline (0.35 m) in water level at the spring; and (3) a significant change (p = 0.0001) in wetted area in winter. Recovery of water levels and wetted area of the mound spring took over three years after pumping ceased. Our study demonstrated that significant changes to the wetted area occurred with only a minimal drawdown at the springs. Abercorn Springs have a natural low variability in water level (<0.2 m), implying a stable and predictable biological community. This natural range is less than half the water level change that is currently considered for impact assessment in artesian springs in the Queensland section of the GAB, highlighting the need to incorporate updated information to inform future management of both recharge and discharge springs. In the case of Abercorn Springs, long-term monitoring and research have led to refinement of license conditions for groundwater extraction, thereby mitigating further impacts to the springs and demonstrating adaptive management. Full article

This study presents a novel approach that integrates the Kalman filter and genetic algorithms to obtain the hydraulic parameters of a confined aquifer with precision, eliminating noise that is not normally considered in traditional procedures; these parameters are necessary for the design of wells, the calculation of water balances and the numerical modeling of aquifers. The Theis solution for horizontal radial groundwater flow to an extraction well within a confined aquifer is implemented in the Kalman filter to calibrate the hydraulic transmissivity and the storage coefficient, minimizing the differences between drawdown estimates and the Theis solution by means of genetic algorithms. The estimate error variances provided by the method allowed for the quantification of an approximate average drawdown measurement error of 0.12 m and 0.02 m, respectively, during the execution of two pumping tests. Full article

To ensure the stability of deep foundation pits in confined aquifers, dewatering is often required. However, pumping from confined aquifers in large deep foundation pit groups may lead to significant environmental deformations. Therefore, field pumping and recharge tests are required to guide design of groundwater and environmental deformation control scheme. Focusing on a super-large deep foundation pit group in Shanghai, single-well pumping, multi-well pumping, and recharge tests were conducted in distinct geological zones (normally consolidated area and paleochannel zone). The hydraulic connectivity and spatiotemporal patterns of groundwater drawdown and soil settlement were systematically analyzed. The results show that: (1) There exists a certain hydraulic connection between the first and second confined aquifers. In the paleochannel area, the aquitard between the micro-confined and the first confined aquifer is insufficient to completely block hydraulic connectivity. (2) The ratio of ground surface settlement to groundwater drawdown is about 3.4 mm/m, and the deep soil settlement is significantly or even greater than the surface settlement, so it is necessary to strengthen the monitoring of deep settlement. (3) Recharge can elevate the groundwater and reduce settlement; however, it is difficult to eliminate the variation in settlement along the vertical direction. Full article

Groundwater recharge is critical for sustainable water management in water-scarce regions like North Algeria, where climate change and urbanization exacerbate resource challenges, particularly in the populous Algiers watershed. This study evaluates groundwater recharge potential using the Analytical Hierarchy Process (AHP) and its fuzzy extension (FAHP), integrated with Geographic Information Systems (GIS), to map recharge zones. Employing open-source data, AHP and FAHP assessed factors such as lithology, slope, and rainfall, classifying the watershed into high, moderate, and low recharge potential zones. Results show AHP identifying 44.01% (528.95 km²) as high, 52.82% (634.93 km²) as moderate, and 3.18% (38.14 km²) as low potential, with FAHP yielding similar outcomes (44.35%, 52.47%, and 3.17%, respectively). Validation using borehole drawdown data confirmed a 73.3% accuracy and an AUC of 0.72, indicating moderate to good reliability. High recharge zones were concentrated in the central and northern areas with permeable soils and gentle slopes, moderate zones dominated the region, and low zones were minimal. This study concludes that both AHP and FAHP are effective for preliminary recharge assessments, with AHP favored for its simplicity, though FAHP excels with uncertain data. Limited high-resolution hydrogeological data highlight the need for further refinement, yet the approach offers a replicable framework for managing groundwater in arid, urbanized regions facing similar environmental pressures. Full article

In order to exploit the deep underground space, the construction of ultra-deep excavation in Shanghai is growing rapidly. In multi-aquifer strata, deep excavations typically require dewatering of confined aquifers to ensure engineering safety. However, existing studies have seldom conducted in-depth analysis on the influence of the soil parameters and construction measures on the deformation of retaining structures. In this study, a three-dimensional hydro-mechanical numerical model was developed to evaluate the performances of excavation and dewatering of the foundation pit. The model was validated by comparing the calculated and measured wall deflections and groundwater drawdowns of a 45 m ultra-deep double-wall excavation in Shanghai. According to the characteristics of soil stratification and construction activities, three parameters were selected for subsequent analysis, including the hydraulic conductivity of aquitard below the bottom of the pit, the pumping rate in the second confined aquifer and the construction of TRD wall. The stress distributions on both sides of the diaphragm wall were examined to elucidate the deformation mechanism. The results indicate that the aquitard hydraulic conductivity directly affects the effective stress of the overlying aquifer, which plays a crucial role in resisting wall deflection. An increase in the hydraulic conductivity leads to smaller effective stress, greater wall deflection and larger ground settlement. While an appropriately increased pumping rate enhances effective stress, over-pumping may induce excessive wall deflection at depth and disproportionate ground settlement. The TRD wall is quite useful in terms of waterproofing but the effect on deformation control is limited. The findings of this study provide valuable insights for engineering practices and the optimization of deep excavation construction measures in multi-aquifer strata. Full article

As shallow coal resources in China become increasingly depleted, deep coal mining in complex geological areas has become an inevitable trend. However, the technical challenges associated with deep mining are becoming more significant, particularly the issues related to mine water hazards. This study utilized hydrogeological data from the III3 Mining Area in the Zhuxianzhuang Coal Mine, Anhui Province, and employed GMS (Groundwater Modeling System) software to construct a numerical karst water flow model under deep mining conditions. By simulating variations in the flow field, the study verified the drainage potential of the limestone water at the base of Seam 10 and assessed the water conductivity and connectivity of the F22 fault. The following conclusions were obtained: The simulation effectively captured the formation process of the karst water drawdown cone in the study area. The observed water level variations in different monitoring wells aligned well with the engineering reality after validation. The limestone water at the base of Seam 10 in the III3 Mining Area exhibited good transmissivity, weak recharge, and high drainage potential. Although the F22 fault is a normal fault with a maximum displacement of 550 m, offsetting formations from Seam 3 to the Ordovician limestone, its connectivity and water conductivity are poor, exhibiting significant water-blocking properties. The specific capacity (q) ranges from 1.40 × 10⁻⁴ to 3.26 × 10⁻³ m³/(s·m), and the hydraulic conductivity (K) ranges from 2.10 × 10⁻⁵ to 6.80 × 10⁻⁵. Under deep coal mining conditions, the extraction of coal disturbs the underlying limestone, generally resulting in an increase in its permeability coefficient compared to pre-mining conditions. The permeability coefficient (K) from the measured data before mining impact ranged from 0.000067 to 0.0022, while the simulated values after mining impact ranged from 0.0021 to 0.09. Additionally, mining activities affect the hydraulic head, flow rate, and flow paths of the karst water; the floor karst water is easily drainable, effectively reducing water pressure and the inrush coefficient, thus lowering water hazard risks. Although the mining area is affected by the large F22 fault, its water-resisting properties under sufficient drainage conditions prevent direct connectivity between the coal seam and the aquifer, avoiding water hazards. As global coal resources continue to be exploited, deep mining will inevitably become a common trend in coal extraction worldwide. This study develops a hydrogeological model tailored to deep mining under fault conditions, offering a solid theoretical foundation and practical reference for the prevention and management of mine water hazards on a global scale. This advancement contributes to the development of sustainable mining practices across the global industry. Full article

Long, narrow, deep excavations commonly encountered in practice, such as those for subway stations, require effective groundwater management to prevent disasters in water-rich areas. To achieve this, a cut-off curtain and pumping well are typically employed during long, deep foundation pit dewatering. The unsteady groundwater flow behavior in the confined aquifer must consider the influence of the cut-off curtain during dewatering. This paper establishes a two-dimensional analytical model to describe transient groundwater flow in a confined aquifer with a cut-off curtain. Both the dewatering well pumped at a steady discharge inside the pit and the cut-off curtain are partially penetrating in the anisotropic confined aquifer. With the help of the Laplace and Fourier cosine transformations, the semi-analytical drawdown solution for the model is derived and validated against numerical solution and unsteady pumping test data. It is shown that the inserted cut-off curtain depth and the structural parameters of the pumping well significantly affect the drawdown inside the pit. Sensitivity analysis reveals that, regardless of whether the observation is made inside or outside the curtain, the drawdown is very sensitive to the change in pumping rate, aquifer thickness, storage coefficient, and horizontal hydraulic conductivity. Additionally, drawdown near the cut-off curtain outside the pit is sensitive to the vertical hydraulic conductivity of the aquifer, the width of the pit, and the interception depth of the cut-off curtain, while drawdown far from the curtain outside the pit is not sensitive to the location and length of the well screen. Full article

The Water–Ecosystem–Agriculture (WEA) relationship is pivotal to the sustainable development of arid and semi-arid areas. The WEA nexus in these areas is essential for making policies towards sustainable development. This study aims to explore the WEA nexus in three large inland river basins (Heihe River Basin, Shiyang River Basin, and Shule River Basin) in the Hexi Corridor, Northwest China, using an integrated hydrological modeling approach. The integrated model was calibrated and validated against observed streamflow data, achieving Nash–Sutcliffe Efficiencies ranging from 0.83 to 0.94 in the validation period. The major findings are as follows. First, altering the amount of irrigation water significantly affects hydrological and ecological processes in both midstream and downstream areas, influencing the WEA nexus. For example, a 20% reduction in irrigation demand led to a 0.46 billion m³/year recovery in midstream groundwater storage and a 4.3% increase in downstream ecosystem health, but resulted in a 5.4% decrease in midstream agricultural productivity. Second, intense trade-offs among agricultural productivity, ecosystem health, and groundwater sustainability were identified. These trade-offs are highly sensitive to water management strategies, particularly those affecting groundwater sustainability. Third, implementing stricter groundwater-level drawdown constraints significantly improved groundwater sustainability and ecosystem health. Fourth, this study highlighted unique WEA nexus characteristics in each of the three basins. This study provides insights into the understanding the complex WEA nexus, and the quantitative results underscore the trade-offs and synergies within the WEA nexus, providing a foundation for informed decision-making in water resource management. Full article