Journal of Groundwater Science and Engineering

Impact of water table on hierarchically nested groundwater flow system

Jun Zhang, Rong-zhe Hou, Kun Yu, Jia-qiu Dong, Li-he Yin

2024, 12(2): 119-131. doi: 10.26599/JGSE.2024.9280010

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Abstract:
Water table configuration gives rise to hierarchically nested groundwater flow systems. However, there remains a lack of comprehensive understanding regarding the controlling factors of water table and its impact on flow systems. Moreover, it remains challenging to identify characteristics of water table space variation through limited groundwater observations at the regional scale. Based on two ideal two-dimensional cross-section analytical models, this study presents a simplified approach to preliminarily assess the nonlinear interactions between water table variation and three driving factors: Topography, geology and climate. Two criteria, C1 and C2, are utilized to address issues at different scales ranging from basin to local: (i) the influence of various factors on water table configuration; and (ii) the influence of water table on groundwater flow pattern. Then, the Ordos Plateau is taken as an example to explore the role of the water table in nested groundwater systems using the provided approach and criterion. The application of this approach in the Ordos Plateau demonstrates its appropriateness as a practical method for preliminarily determining the characteristics of water table configuration and its impact on flow systems. The study explores the mechanism influencing spatial variation in the water table and improves understanding of the interaction between topography, geology, and climate on groundwater flow patterns.

A combined method using Lattice Boltzmann Method (LBM) and Finite Volume Method (FVM) to simulate geothermal reservoirs in Enhanced Geothermal System (EGS)

Xiang Gao, Tai-lu Li, Yu-wen Qiao, Yao Zhang, Ze-yu Wang

2024, 12(2): 132-146. doi: 10.26599/JGSE.2024.9280011

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Abstract:
With the development of industrial activities, global warming has accelerated due to excessive emission of CO₂. Enhanced Geothermal System (EGS) utilizes deep geothermal heat for power generation. Although porous medium theory is commonly employed to model geothermal reservoirs in EGS, Hot Dry Rock (HDR) presents a challenge as it consists of impermeable granite with zero porosity, potentially distorting the physical interpretation. To address this, the Lattice Boltzmann Method (LBM) is employed to simulate CO₂ flow within geothermal reservoirs and the Finite Volume Method (FVM) to solve the energy conservation equation for temperature distribution. This combined method of LBM and FVM is implemented using MATLAB. The results showed that the Reynolds numbers (Re) of 3,000 and 8,000 lead to higher heat extraction rates from geothermal reservoirs. However, higher Re values may accelerate thermal breakthrough, posing challenges to EGS operation. Meanwhile, non-equilibrium of density in fractures becomes more pronounced during the system's life cycle, with non-Darcy's law becoming significant at Re values of 3,000 and 8,000. Density stratification due to buoyancy effects significantly impacts temperature distribution within geothermal reservoirs, with buoyancy effects at Re=100 under gravitational influence being noteworthy. Larger Re values (3,000 and 8,000) induce stronger forced convection, leading to more uniform density distribution. The addition of proppant negatively affects heat transfer performance in geothermal reservoirs, especially in single fractures. Practical engineering considerations should determine the quantity of proppant through detailed numerical simulations.

Delineation of groundwater potential zones using remote sensing and Geographic Information Systems (GIS) in Kadaladi region, Southern India

Stephen Pitchaimani V, Narayanan MSS, Abishek RS, Aswin SK, Jerin Joe RJ

2024, 12(2): 147-160. doi: 10.26599/JGSE.2024.9280012

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The primary objective of this research is to delineate potential groundwater recharge zones in the Kadaladi taluk of Ramanathapuram, Tamil Nadu, India, using a combination of remote sensing and Geographic Information Systems (GIS) with the Analytical Hierarchical Process (AHP). Various factors such as geology, geomorphology, soil, drainage, density, lineament density, slope, rainfall were analyzed at a specific scale. Thematic layers were evaluated for quality and relevance using Saaty's scale, and then integrated using the weighted linear combination technique. The weights assigned to each layer and features were standardized using AHP and the Eigen vector technique, resulting in the final groundwater potential zone map. The AHP method was used to normalize the scores following the assignment of weights to each criterion or factor based on Saaty's 9-point scale. Pair-wise matrix analysis was utilized to calculate the geometric mean and normalized weight for various parameters. The groundwater recharge potential zone map was created by mathematically overlaying the normalized weighted layers. Thematic layers indicating major elements influencing groundwater occurrence and recharge were derived from satellite images. Results indicate that approximately 21.8 km² of the total area exhibits high potential for groundwater recharge. Groundwater recharge is viable in areas with moderate slopes, particularly in the central and southeastern regions.

Modelling the monthly hydrological balance using Soil and Water Assessment Tool (SWAT) model: A case study of the Wadi Mina upstream watershed

Hanane Mebarki, Noureddine Maref, Mohammed El-Amine Dris

2024, 12(2): 161-177. doi: 10.26599/JGSE.2024.9280013

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Modelling the hydrological balance in semi-arid zones is essential for effective water resource management, encompassing both surface water and groundwater. This study aims to model the monthly hydrological water cycle in the Wadi Mina upstream watershed (northwest Algeria) by applying the Soil and Water Assessment Tool (SWAT) hydrological model. SWAT modelling integrates spatial data such as the Digital Elevation Model (DEM), land use, soil types and various meteorological parameters including precipitation, maximum and minimum temperatures, relative humidity, solar radiation and wind speed. The SWAT model was calibrated and validated using data from January 2012 to December 2014, with a calibration period from January 2012 to August 2013 and a validation period from September 2013 to December 2014. Sensitivity and parameter calibration were conducted using the SWAT-SA program, and model performance evaluation relied on comparing the observed discharge at the outlet of the basin with model-simulated discharge, assessed through statistical coefficients including Nash-Sutcliffe Efficiency (NSE), coefficient of determination (R²) and Percent Bias (PBAIS). Calibration results indicated favourable objective function values (NSE=0.79, R²=0.93, PBAIS= −8.53%), although a slight decrease was observed during validation (NSE=0.69, R²=0.86, and PBAIS= −11.41%). The application of the SWAT model to the Wadi Mina upstream watershed highlighted its utility in simulating the spatial distribution of different components of the hydrological balance in this basin. The SWAT model revealed that approximately 71% of the precipitation in the basin evaporates, while only 29% contributes to surface runoff or infiltration into the soil.

Developing three-dimensional groundwater flow modeling for the Erbil Basin using Groundwater Modeling System (GMS)

Jwan Sabah Mustafa, Dana Khider Mawlood

2024, 12(2): 178-189. doi: 10.26599/JGSE.2024.9280014

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This study presents the development of a comprehensive three-dimensional groundwater flow model for the Erbil Basin utilizing the Groundwater Modeling System (GMS). The Erbil Basin, situated in the Kurdistan Region of Iraq, is a vital water resource area facing increasing water demands and environmental challenges. The three-dimensional nature of the groundwater flow system is crucial for accurately understanding and managing water resources in the basin. The modeling process involved data collection, geological and hydrogeological characterization, conceptual model development, and numerical simulation using GMS software MODFLOW 2000 package. Various parameters such as hydraulic conductivity, recharge rates, and boundary conditions were integrated into the model to represent the complex hydrogeological conditions of the basin. Model calibration was performed by comparing simulated groundwater levels with observed data from monitoring wells across the basin, using the automatic calibration method of automated Parameter Estimation (PEST). Pilot points were applied to adjust the hydraulic conductivity in the model area spatially. Sensitivity analysis was conducted to assess the influence of key parameters on model predictions and to identify areas of uncertainty. The developed three-dimensional groundwater flow model provides valuable insights into the dynamics of groundwater flow, recharge-discharge mechanisms, and potential impacts of future scenarios such as climate change and water resource management strategies. It serves as a useful tool for decision-makers, water resource managers, and researchers to evaluate different management scenarios and formulate sustainable groundwater management policies for the Erbil Basin. In conclusion, this study demonstrates the effectiveness of using GMS for developing three-dimensional groundwater flow models in complex hydrogeological settings like the Erbil Basin, contributing to improved understanding and management of groundwater resources in the region.

Characteristics and genesis of groundwater salinization in coastal areas of the Lower Reaches of Oujiang Basin

Mei-hui Zhang, Shi-yang Zhou, Dan-dan Liu, Ying Zhang, Yu-xi Zhang, Xi Chen, Hui-wei Wang, Bei Li, Wei Kang, Bing Yi, Wan-peng Shi

2024, 12(2): 190-204. doi: 10.26599/JGSE.2024.9280015

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The coastal areas of the lower reaches of Oujiang River Basin are rich in groundwater resources. However, the unsustainable exploitation and utilization of groundwater have led to significant changes in the groundwater environment. Understanding the characteristics and genesis of groundwater salinization is crucial for preventing its deterioration and ensuring sustainable utilization. In this study, a comprehensive approach combining the ion ratio method, mineral saturation index method and multivariate statistical analysis was employed to investigate the hydrochemical characteristics and main controlling factors in the study area. The findings reveal that: (1) Groundwater samples in study area exhibit a neutral to slightly alkaline pH. The predominant chemical types of unconfined water are HCO₃-Ca·Na, HCO₃·Cl-Na·Ca and HCO₃·SO₄-Ca·Na, while confined water mainly exhibits Cl·HCO₃-Na and Cl-Na types. (2) Salinity coefficients indicate an increase in salinity from unconfined to confined water. TDS, Na⁺ and Cl^– concentrations show an increasing trend from mountainous to coastal areas in unconfined water, while confined water displays variability in TDS, Na⁺ and Cl^– concentrations. (3) Groundwater salinity is mainly influenced by water-rock interactions, including the dissolution of halite and gypsum, cation exchange, and seawater intrusion etc. Additionally, human activities and carbonate dissolution contribute to salinity in unconfined water. Seawater intrusion is identified as the primary factor leading to higher salinity in confined water compared to unconfined water, with increasing cation exchange and seawater interaction observed from unconfined to confined water.

Research progress on temperature field evolution of hot reservoirs under low-temperature tailwater reinjection

Xin Wang, Guo-qiang Zhou, Yan-guang Liu, Ying-nan Zhang, Mei-hua Wei, Kai Bian

2024, 12(2): 205-222. doi: 10.26599/JGSE.2024.9280016

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This paper focuses on the study of the evolutionary mechanism governing the temperature field of geothermal reservoir under low-temperature tailwater reinjection conditions, which is crucial for the sustainable geothermal energy management. With advancing exploitation of geothermal resources deepens, precise understanding of this mechanism becomes paramount for devising effective reinjection strategies, optimizing reservoir utilization, and bolstering the economic viability of geothermal energy development. The article presents a comprehensive review of temperature field evolution across diverse heterogeneous thermal reservoirs under low-temperature tailwater reinjection conditions, and analyzes key factors influencing this evolution. It evaluates existing research methods, highlighting their strengths and limitations. The study identifies gaps in the application of rock seepage and heat transfer theories on a large scale, alongside the need for enhanced accuracy in field test results, particularly regarding computational efficiency of fractured thermal reservoir models under multi-well reinjection conditions. To address these shortcomings, the study proposes conducting large-scale rock seepage and heat transfer experiments, coupled with multi-tracer techniques for field testing, aimed at optimizing fractured thermal reservoir models' computational efficiency under multi-well reinjection conditions. Additionally, it suggests integrating deep learning methods into research endeavors. These initiatives are of significance in deepening the understanding of the evolution process of the temperature field in deep thermal reservoirs and enhancing the sustainability of deep geothermal resource development.

Groundwater and environmental challenges in Asia

Yan-pei Cheng, Fa-wang Zhang, Hua Dong, Xue-ru Wen

2024, 12(2): 223-236. doi: 10.26599/JGSE.2024.9280017

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Asia stands out as the most populous and geographically diverse region globally. The pressing issues of water resource development and the resulting ecological impacts are exacerbated by the region's rapid population growth and economic expansion. Groundwater, a vital source of water in Asia, faces significant disparities in distribution and suffers from unsustainable exploitation practices. This study applies groundwater system theory and categorizes Asia into 11 primary groundwater systems and 36 secondary ones, based on intercontinental geological structures, climate, terrain, and hydrogeological characteristics. As of the end of 2010, Asia's assessed groundwater resources totalled 4.677×10⁹ m³/a, with exploitable resources amounting to 3.274×10⁹ m³/a. By considering the geological environmental impacts of groundwater development and the distinctive characteristics of terrain and landforms, six categories of effect zones with varying distribution patterns are identified. The current research on Asia's groundwater resources, environmental dynamics, and human impacts aims to provide a theoretical foundation for sustainable groundwater management and environmental conservation in the region.

2024 Vol. 12, No. 2

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