Aquifer Types Research Articles

Application of Pumping Tests to Estimate Hydraulic Parameters of Volcanic Aquifers in Lake Tana Basin, Ethiopia

The purpose of this study was to enhance the understanding and sustainable groundwater management of volcanic aquifer systems by estimating key hydrogeological parameters. The transmissivity of a volcanic aquifer system was estimated using analytical solutions based on 68 constant rate and recovery data sets collected from various sources. A combination of hydro-lithostratigraphy and diagnostic plots was employed to identify the aquifer types and flow conditions, which facilitated model selection. Transmissivity of the confined aquifer was modeled using both Theis and Cooper–Jacob methods, with the Theis residual drawdown solution utilized for estimation. For the unconfined aquifer, the Neuman method was used, and the Hantush/Jacob method was employed for leaky aquifers. The results showed that the transmissivity of the Tertiary basalt varied from 0.38 m2/d to 860 m2/d, while the Quaternary aquifer system ranged from 2.33 m2/d to 1.8 × 104 m2/d, indicating an increase in transmissivity with younger volcanic flows. Specific capacity (SC) was estimated for 74 wells and the values ranged from 0.62 to 5860 m2/d. This wide variation of specific capacity and transmissivity showed significant heterogeneity within the volcanic aquifers. This study introduces the innovative application of derivative diagnostic plots in groundwater research, offering an efficient approach for analyzing and interpreting pumping test data to characterize aquifer systems in various hydrogeologic units. This study focuses on aquifer characterization in hard rock formation, demonstrating methods that can be applied to similar geological environments globally. For the Blue Nile basin in general and for the Lake Tana basin in particular, the study result of aquifer characterization will contribute to exploration, development, and improved groundwater management in the region.

Quantitative Classification of Spring Discharge Patterns: A Cluster Analysis Approach

ABSTRACTSprings provide critical water resources that are sensitive to changing climate and catchment processes. In many regions, understanding the temporal variability and spatial distribution of spring discharge is therefore crucial for sustainable water management. Knowledge of these discharge characteristics, organised in a coherent framework, is essential for protecting spring water and preventing shortages. To establish such a framework, we conducted a comparative analysis of long‐term discharge records from 96 springs across Austria. Based on discharge seasonality and autocorrelation, we derived a broad‐scale classification through cluster analysis and explored associations between individual clusters. The identified similarities in discharge patterns were grouped into four distinct spring categories, each demonstrating common behaviour. To determine the main factors influencing discharge across these four groups, we compared their spatial and temporal patterns with regional climate and catchment characteristics. They align with physical drivers of spring discharge, including precipitation frequency and intensity, snow cover duration, and dominant aquifer type. As these factors were not included in the classification procedure, their alignment supports the validity of our statistical approach. We conclude that the quantitative information derived from this analysis provides a valuable complement to traditional spring classification schemes, which are often based on qualitative knowledge. Our proposed strategy refines these classification approaches, enhances objectivity and reproducibility, and promotes conformity across hydrological disciplines.

Groundwater level predictions in the Thames Basin, London over extended horizons using Transformers and advanced machine learning models

This study breaks new ground by using the Temporal Fusion Transformer (TFT) method for groundwater level prediction, addressing the complex dynamics of the Thames Basin aquifer in England. Our research combines extensive hydrological data collected from the Thames Basin with advanced machine learning, where a complex network of rivers and streams substantially affects groundwater dynamics. Unlike previous studies, this research focuses on long-term forecasting with deep learning, offering, for the first time, a 60-day prediction horizon based on daily data. To rigorously examine the model performance and robustness on new, unseen data, we applied the walk-forward validation method and other matrices such as RMSE and R2 coupled with the Holdout technique. The models used were Long Short-Term Memory (LSTM), Attention-based LSTM, LSTM with Bayesian optimisation, Attention-based LSTM with Bayesian optimisation and TFT. They were used on the basin's Chalk, Jurassic Limestone, and Lower greensand aquifers. Whilst both LSTM models were optimised using the Bayesian technique, TFT was applied for its inherent capability in complex time series. Our methodology processed historical groundwater and rainfall data from 2001 to 2023, accounting for the potential lag in aquifer response to the proximity of the river system. The dataset served as training, validation, and holdout for each model, focusing on capturing the dynamic temporal fluctuation. The results clearly showed the superiority of the TFT model in all aquifer types compared to other models across all horizons. The Limestone had the greatest result in the 7-day projections, with an RMSE of 0.02 and R2 of 0.98; Whilst the Chalk and Lower greensand, had RMSEs of 0.03 with R2 values of 0.75 and 0.95, respectively. The Limestone aquifer performed best for the 30-day horizon again (RMSE = 0.06, R2 = 0.85), with the Chalk and Lower greensand aquifer yielding RMSE of 0.04 and 0.12 and R2 values of 0.64 and 0.74, respectively. In the 60 days predictions, the best results were observed in the limestone aquifer with RMSE of 0.09 and R2 of 0.65 in holdout validation. However, in chalk and lower greensand aquifers, the TFT showed RMSEs of 0.05 and 0.15 and R2s of 0.45 and 0.58, respectively. Traditional LSTM models demonstrated limited predictive power compared to the main model TFT, while the attention mechanism slightly improved the accuracy. This study not only sets a new benchmark in hydrological modelling accuracy but also highlights the potential of advanced machine learning in managing complex aquifers and predicting the water table.

3D Hydrogeological Structure Modeling Based on Quantitative Correlation and Identification of Aquifer Types Within Stratigraphic Layers

3D Hydrogeological Structure Modeling Based on Quantitative Correlation and Identification of Aquifer Types Within Stratigraphic Layers

Hydrogeochemical assessment of groundwater in transboundary aquifers along the US-Mexico border and drinking water quality implications for Texas colonias

The groundwater resources in transboundary aquifers are crucial to the development of involved nations. A unified governance strategy based on scientific data is essential for the management of transboundary aquifers. This study presents a comprehensive geochemical analysis of the groundwater quality of private wells along the US-Mexico border in Texas across three transboundary aquifer types. The concentrations of dissolved major ions, trace, and rare earth elements (REE) were measured, and the dissolved organic matter was spectroscopically characterized to evaluate the prevailing water-rock interactions, biogeochemical reactions, and anthropogenic contamination in the groundwater and their susceptibility to future contamination. Groundwater samples were collected from private wells (n = 22) from four representative counties within a section of the Texas-Mexico border (Maverick, Kinney, Dimmit, and Webb Counties). Three distinct aquifer types were revealed from the major ion composition, e.g., a carbonate aquifer within Kinney County (a part of Edwards-Trinity aquifer), an alluvial aquifer with prevailing reducing conditions within Dimmit and Webb Counties (a part of Carrizo-Wilcox aquifer), and an evaporite-rich aquifer within Maverick County. The concentrations of trace elements in the groundwater of each aquifer type were below the MCL of USEPA, however, excessive Sr concentrations were evident mostly in the evaporite-rich aquifer. Our results indicate dissolution of evaporites, and possible anthropogenic contamination may be responsible for the degradation of groundwater quality in Maverick County, raising concern for the viability of the aquifer in the future.

Cross Comparison of GALDIT Method Application in Three Costal Aquifers in Greece

Seawater intrusion into Greece’s coastal aquifers is a prevalent issue. The Greek coastline extends for 15,147 km. Once groundwater sources become contaminated, remediation methods are often challenging, costly, and protracted. This study focuses on three coastal aquifer systems in the Peloponnese region. Initially, the main ions and cations were determined for these aquifers. Hydrochemical analyses revealed elevated concentrations of Na+, Mg2+, Ca2+, SO42−, and Cl−, indicating a significant impact from seawater intrusion. The study evaluates the vulnerability of groundwater to this intrusion. Utilizing Geographical Information Systems (GIS) software (ArcGISPro), maps were created to illustrate each parameter of the GALDIT method. The acronym GALDIT encapsulates the main elements influencing seawater intrusion. Each parameter is analyzed as follows: Groundwater occurrence (including the following aquifer types: unconfined, confined, and leaky confined), Aquifer hydraulic conductivity, depth to groundwater Level above the sea, Distance from the shore (inland distance perpendicular from shoreline), Impact of existing status of sea water intrusion in the area, and Thickness of the aquifer. The final map that emerged from this study shows their vulnerability to seawater intrusion in Peloponnese. Notably, Larissos exhibits lower vulnerability in contrast to the seawater incursion in the other two groundwater systems.

Environmental impact of an anthropogenic groundwater temperature hotspot

Heat emitted by buildings and other infrastructure accumulates in the subsurface. This additional heat can cause a pronounced shift in thermal boundary conditions of the important groundwater ecosystem. Shallow groundwater systems in Central Europe are often inhabited by communities of fauna adapted to cold and stable conditions as well as microorganisms, whose activity is dependent on ambient temperatures. At a local groundwater temperature hotspot of up to 23 °C, caused by a water park, we assessed the environmental impact of this thermal alteration on the shallow groundwater system. The results show that the overall groundwater quality at the site is influenced by anthropogenic land use, compared to wells in a nearby water protection zone. However, neither hydrochemical nor ecological characteristics of groundwater from wells in the vicinity of the water park indicate any significant dependence on temperature. Hence, we conclude that in this eutrophic and anoxic aquifer moderate heat stress does not lead to significant alterations in terms of hydrochemistry as well as microbiological properties. Due to the overall low oxygen concentrations (<1 mg/l), stygofauna is present only occasionally and cannot be used as bioindicators. These results have to be verified for other aquifer types and would benefit from a more in-depth analysis of microbial community composition.

Groundwater Level Prediction Using Machine Learning and Geostatistical Interpolation Models

Given the vulnerability of surface water to the direct impacts of climate change, the accurate prediction of groundwater levels has become increasingly important, particularly for dry regions, offering significant resource management benefits. This study presents the first statewide groundwater level anomaly (GWLA) prediction for Arizona across its two distinct aquifer types—unconsolidated sand and gravel aquifers and rock aquifers. Machine learning (ML) models were combined with empirical Bayesian kriging (EBK) geostatistical interpolation models to predict monthly GWLAs between January 2010 and December 2019. Model evaluations were based on the Nash–Sutcliffe efficiency (NSE) and coefficient of determination (R2) metrics. With average NSE/R2 values of 0.62/0.63 and 0.72/0.76 during the validation and test phases, respectively, our multi-model approach demonstrated satisfactory performance, and the predictive accuracy was much higher for the unconsolidated sand and gravel aquifers. By employing a remote sensing-based approach, our proposed model design can be replicated for similar climates globally, and hydrologically data-sparse and remote areas of the world are not left out.

Improving Fault Zones Hydrodynamic Characterization and Simulation in Karstified Carbonate Environments with GLM and IES Invers Methods

A quantitative and qualitative estimation of groundwater resources is a challenge for water management worldwide. In the specific case of the carbonate karstified aquifer, the high sensitivity of this resource is partially due to its level of permeability. Moreover, the extreme heterogeneity of this type of aquifer makes it complex to define vulnerable areas, especially when fault zones exert a significant influence on groundwater hydrodynamics and transport. Improving the management of this type of aquifer involves better assessment of its hydrodynamics properties. Sustainability and management solutions can be estimated through numerical modeling. In this study hydrodynamic parameter of the fault zone in karstified carbonate environments are estimated from cross-hole pumping test data. These analyses allow the simulation and forecasting of fault zone flow and travel time. For this purpose, a flow and travel time model has been set up using MODFLOW6 and MODPATH7 codes. Inverse modeling of hydrodynamic parameters is performed with the PEST++ code suite, with both the Gauss-Levenberg-Marquardt Algorithm (GLM) and the Iterative Ensemble Smoother (IES) which is a recent approach with few applications so far. Simulation, parameter estimation, and forecasts of drawdown and pollutant travel time through the fault zone have been first evaluated on a synthetic fault zone and are eventually applied to a real-world fault zone of interest in karst carbonate environments. A comprehensive comparison and analysis of GLM and IES results are performed for parameter estimation, parametric and predictive uncertainties, ensuring a thorough assessment of results. The numerical inversion approach provided a spatial parametric estimation of the hydraulic conductivity of the fault zone, along with an uncertainty analysis.This approach demonstrates its ability to estimate the hydrodynamic parameter field with a high level of accuracy within the internal structures of the fault zone. This study constitutes valuable and reproducible insights into the simulation and forecasts of fault zones in karst carbonate aquifers. The findings are a step forward in groundwater flow and travel time simulation of fault zones and provide relevant practical help for the management and protection of water resources in these critical areas of interest.

Tracking abiotic transformation of 1,1,1-trichloroethane to 1,1-dichloroethylene in contaminated groundwater on a national scale

1,1,1-trichloroethane (TCA) is a chlorinated aliphatic compound that was increasingly applied as a replacement for trichloroethylene. TCA can simultaneously follow two abiotic degradation processes: hydrolysis and dehydrochlorination, where the latter lead to the formation of a relatively recalcitrant product 1,1-dichloroethylene (DCE). The abiotic processes are relatively rapid and can be assessed based on the ratio between TCA and DCE. Using national data collected in Israel since the year 2000, this work aimed to examine the abiotic degradation extent of TCA nationally and whether it is affected by the aquifer type and unsaturated zone thickness. We have also examined temporal shifts in TCA and DCE concentrations and tested whether they follow expected trends. Our results show that the abiotic degradation of TCA is significant on a national scale, with higher DCE over TCA concentrations in ≈ 89 % of the wells. Furthermore, in ≈ 85 % of the data points, TCA over DCE concentrations indicate that TCA underwent three or more half-lives. Comparing the different lithologies of contaminated groundwater, higher concentrations are observable in karst relative to unconsolidated aquifers. Nevertheless, the ratio between the two and correspondingly the degradation rates are not affected by lithology. Finally, temporal shifts in TCA and DCE concentrations, as well as the ratio between the two, are different than expected in an idealized closed system. Complexities such as lithological heterogeneity, multiple sources, transport parameters, and more must be considered in interpreting these trends when quantification of the degradation rate is attempted.

Aquifer Leakage Recharge Controls on CBM Production: A Case Study in the Sanjiao Block, Eastern Ordos Basin, China.

Aquifer leakage recharge poses a prevalent challenge in coalbed methane (CBM) development, severely impeding its efficient production. This study focuses on the Sanjiao Block, located on the eastern margin of the Ordos Basin, and provides a comprehensive evaluation of the impact of aquifer leakage recharge on CBM well productivity, employing hydrochemical characteristics and numerical simulation. Fisher's discriminant analysis reveals a close association between external water sources for CBM wells in the Taiyuan Formation and the hydrodynamic environment: in the western stagnant zone, hydrochemical characteristics resemble those from the Shanxi Formation; in the eastern strong runoff zone, water from the Taiyuan Formation directly contributes to CBM well development; in the central weak runoff zone, hydrochemical characteristics suggest mixed water sources from the Shanxi Formation and Taiyuan Formation. The numerical simulation employs orthogonal experiments to quantify the sensitivity of aquifer geological parameters to CBM production, ranked from strong to weak for aquifer types, leakage channel properties, and aquifer physical properties. The fundamental reason for disparities in the efficacy of leakage recharge lies in categorizing aquifers into finite and infinite recharges based on their water supply capacity. The properties of leakage channels, including the location and scale, manifest as effects on the magnitude and shape of gas production characteristics in infinite and finite recharge aquifers, respectively. Furthermore, a discriminant flowchart of CBM production is presented, delineating the production characteristics of CBM wells under the influence of aquifer leakage recharge into six patterns and illustrating their distribution in the study area. This discriminant process provides scientific guidance for analyzing CBM production characteristics and evaluating potential under the influence of aquifer leakage recharge.

Seasonal dynamics of dissolved inorganic nitrogen in groundwater: Tracing environmental controls and land use impact

High levels of dissolved inorganic nitrogen (DIN) in groundwater pose challenges for regions like northern Anhui Province, China, where groundwater is a crucial domestic resource. This study utilized modern geostatistics to explore the spatial and temporal dynamics of DIN in groundwater. Significant seasonal influences on DIN concentrations were identified: ammonium peaks during wet season driven by agricultural activities, while nitrate peaks during the dry season primarily influenced by municipal inputs. This study established a Bayesian Maximum Entropy - Random Forest (BME-RF) model based on Land Use/Land Cover data to infer the spatio-temporal performance of DIN, achieving an interpretation rate above 90 %. It also highlighted the role of hydrogeological conditions and aquifer types in the evolution of DIN. By employing a DIN environmental interaction model, it further analyzed the eco-hydrological drivers and seasonal trends affecting DIN variability, enhancing the understanding of groundwater nitrogen dynamics and their link to environmental factors with low consumption. SynopsisThis study reveals seasonal shifts in groundwater DIN, links them to human activity, and uses the BME model to guide targeted nitrogen fluctuation.

Hydrogeochemical evolution patterns of diverse water bodies in mining area driven by large-scale open-pit combined underground mining-taking Pingshuo Mining Area as an example

Large-scale open-pit combined underground mining activities (OUM) not only reshape the original topography, geomorphology, and hydrogeochemical environment of the mining area, but also alter the regional water cycle conditions. However, due to the complexity arising from the coexistence of two coal mining technologies (open-pit and underground mining), the hydrological environmental effects remain unclear. Here, we selected the Pingshuo Mining Area in China, one of the most modernized open-pit combined underground mining regions, as the focus of our research. We comprehensively employed mathematical statistics, Piper diagram, Gibbs model, ion combination ratio, principal component analysis and other methods to compare the hydrochemistry and isotope data of different water bodies before (2006) and after (2021) large-scale mining. The changing patterns of hydrochemical characteristics of different water bodies and their main controlling factors in mining area driven by OUM were analyzed and identified, revealing the water circulation mechanism under the background of long-term coal mining. The results showed that: (1) The chemical composition of water has changed greatly due to large-scale coal mining. The hydrochemical types of Quaternary and Permian-Carboniferous aquifers shifted from predominantly HCO3-Ca·Mg before intensive mining to primarily HCO3·SO4-Ca·Mg, HCO3-Na, HCO3·SO4-Na·Mg, and HCO3·SO4-Ca·Mg, HCO3-Ca·Na, HCO3·SO4-Mg·Ca post-mining. Variations in the hydrochemical types of surface water were found to be complex and diverse. (2) Coal mining activities promote the dissolution of silicate rock and sodium-bearing evaporites, enhancing the strength and scale of positive alternating adsorption of cations. The oxidation of pyrite, dissolution of silicate weathering, and the leaching of coal gangue were identified as the main reasons for the significant increase of SO42−, while decarbonation in confined aquifers led to a decrease in HCO3−. (3) Results from the principal component analysis and stable isotopes demonstrated the hydraulic connection among surface water, Quaternary aquifers, and Permian-Carboniferous aquifers induced by long-term OUM. The research findings provide a reference basis for the coordinated development of coal and water in the Pingshuo Mining Area and other open-pit combined underground mining areas.

Metagenomic and isotopic insights into carbon fixation by autotrophic microorganisms in a petroleum hydrocarbon impacted red clay aquifer

Autotrophic microorganisms, the pivotal carbon fixers, exhibit a broad distribution across diverse environments, playing critical roles in the process of carbon sequestration. However, insights into their distribution characteristics in aquifers, particularly in those petroleum-hydrocarbon-contaminated (PHC) aquifers that were known for rich in heterotrophs, have been limited. In the study, groundwater samples were collected from red clay aquifers in the storage tank leakage area of a PHC site, a prevalent aquifer type in southern China and other regions. Metagenomics combined with hydrochemical and inorganic carbon isotope analyses were employed to elucidate the presence of microbial carbon fixation and its driving forces. Results showed that there were hundreds of autotrophic microorganisms participating in distinct carbon fixation processes in the red clay PHC aquifers. Reductive tricarboxylic acid (rTCA) and dicarboxylate/4-hydroxybutyrate (DC/4HB), as well as 3-hydroxypropionate (3HP or/and 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB)) were the predominant carbon fixation pathways. The abundances of carbon fixation genes and autotrophic microorganisms were significantly and positively correlated with hydrocarbon concentrations and δ13C of dissolved inorganic carbon (δ13C-DIC) values. This finding indicated that the petroleum hydrocarbon significantly promoted the proliferation of carbon fixation microorganisms, leading to a substantial uptake of inorganic carbon. Therefore, we deduce that this process holds considerable potential for carbon sequestration in PHC-contaminated aquifers.

Groundwater well rehabilitation using hydropuls method: a case study in wonosobo groundwater well

Abstract Hydropuls is one of the groundwater well rehabilitation methods that involves pulsing highly compressed nitrogen gas through screen pipes at an adjustable interval. Nitrogen gas was chosen because of its colorless, odorless, and inert properties. The aquifer lithology of this groundwater well is sand, gravel and breccias (member of Sundoro Volcanics; Qsu) with silty clay as the impermeable layer that makes the aquifer type is confined aquifer. The following methods were used in this well rehabilitation: step tests before, borehole camera before, hydropuls, airlifting, borehole camera after and step test after well rehabilitation. Thin section analysis shows that sediment mostly consists of lithic fragments and plagioclase. The results of the polished section analysis reveal that most of the metallic minerals are magnetite and hematite. The XRF results show that the sediment mostly consists of SiO2, Al2O3 and Fe2O3. According to the XRD results, the sediment is mostly albite. The interpretation of sediment analysis shows that the clogging is caused by iron precipitation. The result is an average increase in specific capacity of 1.43 l/s/m (a 168% increase over the initial conditions) and an average drawdown improvement of 2.56 m (a 114% improvement compared to pre-hydropuls conditions). Borehole camera imaging confirmed that the precipitation on the screen was removed and the screen is in good condition.

APPLICATION OF VERTICAL ELECTRICAL SOUNDING (VES) IN GROUNDWATER AQUIFER ESTIMATION IN THE "SPR" AREA, WONOGIRI DISTRICT, WONOGIRI REGENCY, CENTRAL JAVA

“SPR” area in Wonokarto Village, Wonogiri Regency, Central Java Province, is one area with serious groundwater problems. Regional conditions and significant population growth cause the need for clean water to increase. Efforts to obtain groundwater reserves continue to be made to overcome this problem. Identification of aquifers is carried out using resistivity methods. The research aims to determine the presence and types of an aquifer based on resistivity methods. Using the Schlumberger configuration, data was acquired at ten Vertical Electrical Sounding (VES) points. Results of the research show that in this region, tufa rocks form an aquifer layer in the Quarter Volcan Lava (Qvl) formation, with resistivity ranging from 14.9 to 29.8 Ωm. The “SPR” area has three aquifer types, i.e., surface, shallow, and deep, with (1.5–5) meters, (10.5–25) meters, and (30–129) meters in depth, respectively.

Identifying the origin of springs in weathered-fractured crystalline aquifers using a hydrogeophysical approach

Over the last few decades, important advances have been made in the development of relevant hydrogeological conceptual models for crystalline aquifers, and notably for weathered-fractured crystalline aquifers. Paradoxically and contrary to other types of aquifers, these researches never aimed at characterizing springs, the places were groundwater naturally outflows from such aquifers. With such an objective, our methodological approach consisted first of a lithological and hydrogeological description of the aquifer system based on borehole data and outcrops in a representative weathered-fractured crystalline aquifer (Daloa, Ivory Coast). Next, electrical resistivity tomography (ERT) has been used (after validating the appropriate inversion method) to provide the imagery of the weathering profile both below the plateaus and in the valleys where the springs outflow. Piezometric and river discharge data were also processed notably to determine the direction of groundwater flow. Results demonstrate unambiguously that the isalterites aquifer supplies the springs, and that the underlying fractured layer is not directly implied in this supply. ERT combined with borehole and field lithological data also shows that the lateritic formations (alloterites) present near surface below the plateaus, as well as the upper part of the isalterites, were eroded in the valleys, but not deep enough to let the fractured layer outcrop. This conceptual model for springs not only provides a basis for characterizing such complex aquifers, but also provides technical guidance for spring catchment and groundwater protection in these crystalline areas.

Review: Andesitic aquifers—hydrogeological conceptual models and insights relevant to applied hydrogeology

Research on the hydrogeology of andesitic volcanic aquifers in subduction areas is reviewed. Andesitic aquifers are of high interest in volcanic arc islands and subduction zones, where they constitute a strategic water resource. This review gathers a compilation of worldwide results and case studies to propose a generic hydrogeological conceptual model (GHCM). It is based on the geological conceptual model splitting the volcanic edifice, from upstream to downstream, into central, proximal, medial and distal zones. In this geological structure, the GHCM identifies where the main aquifer types (fractured lava, pyroclastic flows, and the volcano-sedimentary basins downstream) and the typical aquitards (lahars, fine pyroclastic falls and surges, indurated pyroclastic flow, and weathered rocks) are structured and organized. To integrate the evolution of volcanoes and some specific volcanic activities, a specific GHCM for old andesitic volcanoes or andesitic shield volcanoes is detailed. The paper also describes how the GHCM results are of use to hydrogeologists in terms of scale (from the lithological units to the regional scale), to effectively site water wells, and to sustainably manage groundwater resources in such aquifers. Among these various scales, the volcanic “flank continuum” is presented as the most adapted to support groundwater resources management. Several ways to improve this GHCM are suggested, notably to better consider the geological complexity of these aquifers.

Integrating MODFLOW and machine learning for detecting optimum groundwater abstraction considering sustainable drawdown and climate changes

Detecting optimum groundwater abstraction is a challenging objective. This study proposes a new approach for identifying the optimum pumping rates by integrating MODFLOW with machine learning (ML). The adopted strategy has been applied to the Oligocene and Eocene aquifers in the western desert of Minia, Egypt. MODFLOW-2005 model has been utilized to simulate various management scenarios, including current and expected climate scenarios of two Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. The steady-state and transient MODFLOW models were calibrated using the groundwater levels of 37 observation wells with a coefficient of correlation (R2) of 0.986 and 0.988, respectively. The developed model has been run for 80 years, from 2020 to 2100. The results of MODFLOW demonstrated a drawdown in the groundwater level in the two aquifers, about 40, 41, and 42 m, owing to current climate conditions and scenarios of RCP 4.5 and RCP 8.5, respectively, in 2100. Generated data based on the calibrated model has been used to develop the ML models. ML models have been applied to predict the pumping rates using the well coordinates, aquifer type, evapotranspiration, the operating period in days, and drawdown as inputs. For this purpose, four ML models, Gaussian Process Regression (GPR), Support Vector Regression (SVR), Tree, and Artificial Neural Network (ANN)) were developed and evaluated. All ML models demonstrated an effective performance during the training and validation processes, particularly the GPR model, which has the best ability to predict the pumping rates with a correlation coefficient, RMSE, and Mean Absolute Error (MAE) equal to 1.0, 6.53, and 8.04, respectively. Therefore, the GPR model has been utilized to identify the optimum pumping rates. The findings of the GPR model revealed that the optimum abstraction of the Oligocene aquifer is 602266, 625329, and 635061 m3/day, while the Eocene aquifer’s optimal groundwater abstraction is 10229801, 1027906, and 102936 m3/day, considering the current climate, RCP 4.5, and RCP8.5, respectively. Anticipated findings are supposed to be instrumental for decision-makers, offering valuable insights into sustainable groundwater management. The novel integration methodology promotes the efficient use of groundwater, contributing to achieving sustainable development goals (SDGs).

Hydrogeochemical evolution and processes based on multivariable statistical and inverse simulation modeling: A coal mine in the Northern Coalfield, China

ABSTRACT Considering groundwater from the aquifers overlying the bedrock is an important water source for drinking purposes. As such, the investigation of its property is essential. Based on the spatial structure of aquifers in the study area, the aquifers in the Cenozoic strata are divided into three groups. The multivariate statistical approaches are employed to identify the hydrogeochemical processes and hydro-chemical types, and hydrogeochemical inverse modeling is applied to further validate and elucidate the hydrogeochemical process and water–rock interaction. The results are as follows: (1) The hydro-chemical type of the upper aquifer is dominated by the K + Na-HCO3 type, while others have similar water quality types, which are dominated by the K + Na-Cl type and the K + Na-SO4 type. (2) The saturation index of anhydrite, gypsum, halite, and CO2(g) is below zero in three aquifers, indicating that they are unsaturated. While aragonite, calcite, and dolomite in the middle aquifer remain in the unsaturated–saturated state. (3) The cation exchange process accelerating the reduction of Ca2+ concentration and the increase of SO42− concentration occurs in three aquifers, and the dissolution of calcite and dolomite minerals occurs in most cases. This study supports the fundamental evidence for the hydrogeochemical processes and water resource utilization and has a certain practical significance.