Groundwater Behavior Research Articles

Analytical study on 2D groundwater flow in a sloping unconfined aquifer under spatiotemporal recharge

This study presents a two-dimensional (2D) model for simulating groundwater level variations in sloping aquifers, where rainfall is the primary recharge source. The model uses Heaviside functions to represent spatiotemporal surface recharges and is based on the 2D linearized Boussinesq equation. Analytical solutions were derived using an integral transformation method, allowing for analysis of aquifer characteristics, such as anisotropy, slope, and hydraulic conductivity. In contrast to studies that assume total rainfall becomes recharge, this model employs Horton’s infiltration equation for more accurate estimates, showing strong alignment with field data. The results highlight the significant impact of anisotropy on groundwater flow, particularly when the hydraulic conductivity ratio Kx/Ky\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{x}/{K}_{y}$$\\end{document} exceeds 10, leading to predominantly X\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X$$\\end{document}-direction flow, with the flow rate increasing by 1.3 times compared to the scenario where Kx/Ky=1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{x}/{K}_{y}=1$$\\end{document} under slope angles θx=θy=5∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ heta }_{x}={\ heta }_{y}=5^\\circ$$\\end{document}. This model also aids in predicting groundwater behavior in small watersheds without field data.

Convolutional long short-term memory neural network for groundwater change prediction

Forecasting groundwater changes is a crucial step towards effective water resource planning and sustainable management. Conventional models still demonstrated insufficient performance when aquifers have high spatio-temporal heterogeneity or inadequate availability of data in simulating groundwater behavior. In this regard, a spatio-temporal groundwater deep learning model is proposed to be applied for monthly groundwater prediction over the entire Choushui River Alluvial Fan in Central Taiwan. The combination of the Convolution Neural Network (CNN) and Long Short-Term Memory (LSTM) known as Convolutional Long Short-Term Memory (CLSTM) Neural Network is proposed and investigated. Result showed that the monthly groundwater simulations from the proposed neural model were better reflective of the original observation data while producing significant improvements in comparison to only the CNN, LSTM as well as classical neural models. The study also explored the performance of the Masked CLSTM model which is designed to handle missing data by reconstructing incomplete spatio-temporal input images, enhancing groundwater forecasting through image inpainting. The findings indicated that the neural architecture can efficiently extract the relevant spatial features from the past incomplete information of hydraulic head observations under various masking scenarios while simultaneously handling the varying temporal dependencies over the entire study region. The proposed model showed strong reliability in reconstructing and simulating the spatial distribution of hydraulic heads for the following month, as evidenced by low RMSE values and high correlation coefficients when compared to observed data.

A hydrogeophysical conceptual model in the exploration of the "Las Sierras" aquifer: Case of Subwatershed III, southeast sector of Lake Managua, Nicaragua

This study proposes a hydrogeophysical conceptual model in a region southeast of Sub-basin III, which is part of the "Las Sierras" aquifer. The methodology employed combines geological data obtained from wells with geo-electric profiles, thus allowing a more precise representation of an underground valley hitherto unknown, primarily related to the materials of the Middle Las Sierras Group (TQps-M), identified as the main aquifer in the area. The delineation of hydrogeological units was carried out considering geological and geophysical conditions, providing valuable information to understand the distribution and behavior of groundwater in the region. The precise identification and delineation of hydrogeological units enable better management of groundwater resources in the region. This more detailed knowledge enables more effective strategies for the preservation and sustainability of local aquifers.

Groundwater–rock interactions and mixing in fault–controlled karstic aquifers: A structural, hydrogeochemical and multi-isotopic review of the Pontina Plain (Central Italy)

Karstic aquifers represent crucial water resources and are categorized as either stratigraphically or fault–controlled. This study investigates groundwater–rock interactions and mixing processes within one of the largest fault–controlled karstic aquifers in Central Italy, adjacent to the Pontina plain, which is a highly populated area where agricultural activities and climate change challenge the groundwater assessment of a complex aquifer. We conducted structural, hydrogeochemical, and multi-isotopic screening of ten selected springs with different degrees of mineralization (ranging from Ca–HCO3 to Na–Cl hydrofacies), incorporating new analyses and modeling of δ34S(SO4), δ18O(SO4), 87Sr/86Sr, and δ11B. Additionally, the reinterpretation of a seismic section provides a more detailed framework extending to depths of approximately 5–7 km that allows the identification of the geometry of normal faults, which act as pathways for upwelling fluids. Our findings reveal that hydrogeochemical compositions result from multiple interactions between karstic water and deeper fluids that have interacted with different rocks. Concentration (Na/Li) and isotope (SO4–H2O) geothermometers, coupled with geochemical modeling and trace element analysis, enabled the estimation of a water temperature equilibrium of approximately 95.5 °C, with Triassic evaporites generally corresponding to a depth of approximately 3 km and a temperature of 40 °C with magmatic rocks at approximately 1 km depth, which is likely associated with ongoing tectonics and the Quaternary tectonically controlled Volsci Volcanic Field. To obtain the latter estimate, we used a new geothermometer activity based on the equilibrium between analcime and pollucite. Furthermore, this multidisciplinary approach enhances the understanding of groundwater behavior in fault–controlled karstic aquifers, where mantle-derived CO2 dissolved in groundwater is the driving force behind water–rock interactions. Given the potential for further variations in mixing, which may worsen water quality and increase aquifer vulnerability, periodic monitoring of these processes is essential in a human-impacted environment amidst ongoing climate change.

Corrosive behavior of copper canisters under air and aerobic groundwater at early stages of deep geological disposal

Copper oxidation at low temperatures below 140 °C and its effects on corrosive behavior in aerobic groundwater are investigated to estimate the intactness of canisters at early stages of disposal. The Cu coupon surface is covered by fine particles that form thin oxide layers after 30 d of oxidation; a thin Cu2O layer of thickness <100 nm is formed after oxidation at 40 °C; after oxidation at 140 °C, the Cu2O surface changes to a CuO layer of thickness <500 nm. The thickness of the Cu surface oxidized at 90 °C is between those of the surfaces oxidized at 40 and 140 °C. All Cu coupons exhibit similar current densities ranging from 0.77 to 1.87 μA cm−2, although the corrosion potential of the Cu coupon layered with Cu2O is higher than that of the others. Long-term oxidation tests for 406 d reveal no significant changes in the Cu surface at temperatures below 90 °C, indicating no significant change in the electrochemical behavior. The results of this study suggest that the storage of canisters at temperatures below 90 °C has no significant effect on the degradation of canister performance in long-term disposal.

Assessing the Impact of Groundwater Recharge on Underground Reservoir Replenishment in Eastern Uttar Pradesh, India

Groundwater is considered a fresh resource of water and its uses have tremendously increased in the recent past due to an increase in population, rapid urbanization, and industrialization. In India, the groundwater level is declining in some parts of the country due to over-exploitation, low or negligible recharge of aquifer systems, and unsustainable development of groundwater resources. The groundwater modeling is an important tool for studying the past and present groundwater behavior and in the development of future strategies for sustainable groundwater management plans. To study the Impact of groundwater recharge on the replenishment of underground reservoir, Ballia district of Uttar Pradesh has been selected which is one of the districts of the most populous state of India, Uttar Pradesh. An attempt has been made to develop a groundwater model using Modflow software to simulate the groundwater trends and predict future groundwater heads. The calibration and validation of the model were done for 5 years and 3 years respectively. The correlation coefficient for calibration and validation was found 0.85 and root mean square errors vary from 2.89 to 3.2m variation in future trends of groundwater heads. The results of the study show that the developed model can be effectively used to predict the future groundwater heads. The groundwater flow was observed from the northwest to southeast direction. It was predicted from the study that groundwater draft will increase by 10% with a decrease in groundwater level by approximately 0.24 m in the north-west direction by the year 2025. However, no impact was observed in the south side of the district and it was predicted that the groundwater level would remain the same in this zone during the next 3 years.

Influence of precipitation infiltration recharge on hydrological processes of the karst aquifer system and adjacent river

Understanding the hydrological processes of the karst aquifer system (KAS) and adjacent river can further accurately evaluate karst water storage. However, the mechanism of the KAS and adjacent river hydrological processes under precipitation infiltration recharge conditions, the micro-flow behavior of groundwater in the KAS, and changes in media saturation remain unclear. This study coupled the KAS and adjacent river through the Volume of Fluid (VOF), simulated the flow behavior of groundwater in different medium of the KAS and coupled the free flow process of the adjacent river by using the multiphase Darcy-Brinkman-Stokes (DBS) equation, applied the van Genuchten-Mualem and van Genuchten-modified Mualem equations to characterize the seepage processes in soil. The results indicate that the saturation of different porous media controlled by recharge intensity directly influences the flow behavior and flow paths of the porous media. The main groundwater flow path under low precipitation intensity (b=3) is primarily the lower porous medium, while under moderate precipitation intensity (3<b≤8), the main flow path of groundwater is the karst conduit. During heavy precipitation (8<b≤12), due to the limited capacity of karst conduit, they cannot bear the large amount of groundwater supplied from upper porous medium. The peak conduit saturation in laminar flow is 0.3 lower than that in turbulent flows. Under laminar flow conditions, the conduit drainage leads to a rapid decrease in saturation, making it easier for porous media to recharge to the conduit and discharge towards the adjacent river. The turbulent state conduit maintains a high saturation recession, but the discharge is consistently lower than laminar flow. The variation process line of average flow velocity and interfacial flow velocity are obtained using the DBS method and N-S simulation method respectively. There is a certain discrepancy between the simulation results of the two methods since the N-S simulation scheme dose not consider the water retention characteristics of the porous medium.

Assessing groundwater behavior and future trends in the Ardabil Aquifer: A comparative study of groundwater modeling system and categorical gradient boosting hybrid model

Rapid population growth and rising demand have led to increased groundwater extraction, underscoring the importance of effective water resource management. While groundwater models are practical tools, their reliance on extensive hydrogeological and hydrological data can pose challenges when such data is unavailable or inaccessible. In this study, two modeling approaches were employed for the prediction and characterization of groundwater behavior in Ardabil Plain from October 2010 to March 2021. Initially, groundwater behavior was modeled using Modflow. Subsequently, the groundwater behavior was modeled within the same time frame using the hybrid CatBoost-AOA model. Groundwater levels were then determined using these two models until the year 2031. The CatBoost-AOA hybrid method showed the highest agreement (correlation coefficient: 0.9977). Modflow and CatBoost models predicted a decline of 0.77 and 0.85 m, respectively, until 2031. This study aims to guide sustainable development planning, with CatBoost-AOA providing a simplified and efficient alternative for accurately forecasting groundwater fluctuations.

Groundwater vulnerability and risk assessment coupled with hydrogeochemical analysis in the Taza aquifer (Morocco)

This study assesses the vulnerability of aquifers to increased contamination, influenced by rapid peri-urbanization and deficient sanitary infrastructure. The research focuses on the Taza aquifer in northeastern Morocco, where we applied the DRASTIC and GOD models. We further enhanced the DRASTIC method by the addition of a Fracture Index (F) ‘’DRASTICF‘’ to incorporate the effects of tectonics and geological discontinuities on groundwater behavior. The vulnerability mapping was performed for two distinct dry and wet periods of 2016 and 2021 respectively. Moreover, the use of hydrogeochemical analysis of 22 groundwater samples helped to identify potential sources of pollution and to understand the hydrogeological process. The results indicate a dynamic in vulnerability between these two periods due to changes in the recharge parameter and groundwater depth. The comparison between obtained vulnerability maps and nitrate concentrations reveals vulnerable zones that closely resemble regions affected by nitrate pollution. This area is predominantly classified as of high vulnerability at 27 %, associated with an estimated pollution level of 36%. The findings underscore also the importance of integrating the fracture index into the assessment of aquifer vulnerability alongside the different models. This integration offers an enriched perspective for effectively managing risks associated with groundwater contamination. The risk maps of groundwater contamination were also established by overlapping the vulnerability map with the land use layer. The main hydrogeochemical facies determined in the Piper Diagram allowed classifying the waters as Ca–Mg–HCO3 type. The significant correlations indicated that groundwater mineralization in the study area originates from the dissolution of limestone and evaporated formations. The water quality within the study area shows substantial variability, ranging from excellent to unsuitable, primarily due to the leaching of fertilizers and wastewater.The different results can be very helpful to the farmers, and local authorities for better groundwater sustainable management.

Groundwater exhibits spatially opposing trends during the Australian Millennium Drought

The adverse impacts of Australia’s Millennium Drought on both surface and groundwater hydrological systems are extensively documented. During the Millennium Drought, the Murray Basin experienced a severe rainfall deficit. Our study revisited groundwater table trends in 451 wells within the Murray Basin during the drought from 1997 to 2009. These trends varied, 70% showed significant downward shifts, 19% were insignificant, and 11% even displayed upward trends. The results from K-means clustering analysis indicate a markedly slow recuperation of groundwater levels post-drought. We used multiple regression models to link interannual groundwater dynamics with climate variables, revealing climate as the primary driver of declining groundwater levels. This connection is influenced by land cover and thickness of the vadose zone, resulting in hysteresis effects and spatial variations. In cases with a thick vadose zone and minimal evapotranspiration, the influence of the Millennium Drought on the groundwater system is reduced. The increasing trends may also be related to lateral recharge from mountainous areas, human activities in adjacent irrigation districts, and east-west geostress. Our findings reveal the complex interactions between climate, land characteristics, and groundwater behavior during and after the Millennium Drought, holding significant implications for understanding hydrological processes under extreme drought conditions and for the sustainable management of water resources.

Evaluating tidal impact on ground source heat exchanger performance under fluctuating groundwater levels

Coastal regions undergo dynamic changes due to tidal forces, posing distinct challenges for groundwater management and utilization of ground source heat pump (GSHP) systems. This study examines the impact of tidal fluctuations on groundwater levels and the performance of ground heat exchangers (GHEs), specifically focusing on the suitability of horizontal directional drilling (HDD) technology in high-tidal zones. Itoman City in Okinawa Prefecture, Southern Japan, serves as an ideal location for this study due to its complex coastal hydrogeological conditions and increasing interest in renewable energy solutions. Employing a comprehensive approach involving field experiments, FEFLOW software simulations, and model validation, we aim to elucidate the intricate relationship between tidal dynamics, groundwater behavior, and GHE performance. Furthermore, our investigation assesses the effectiveness of HDD-GHEs installed in highly tidal-affected zones to determine the optimal installation depth for this type of GHE in coastal regions. According to our research, the layer at a depth of 30 m is most affected by tidal influence and fluctuations in groundwater levels in coastal regions. This layer is the most suitable for installing horizontal HDD-GHEs, with an average heat exchange rate of about 89 W/m. This rate is approximately four and two times higher than the depths above and below this layer, respectively, due to groundwater saturation and flow in the formation. Furthermore, we noticed that the heat exchange rate increases from the top to the bottom of this layer, but the extent of this increase diminishes as the depth increases. This is because deeper depths are less affected by tidal fluctuations in groundwater levels.

Hydrogeochemical Behavior of Shallow Groundwater around Hancheng Mining Area, Guanzhong Basin, China

A total of 18 samples of shallow groundwater around the Hancheng mining area in the Guanzhong Basin were collected from 1–4 May 2018. According to the analysis of hydrochemical data, the Gibbs semi-logarithmic diagram and Piper diagram were used to research the hydrogeochemical behavior of shallow groundwater around the Hancheng mining area in the Guanzhong Basin. The results of the groundwater hydrochemical analyses shown on the Gibbs and Piper plots are as follows: The chemical composition analysis showed that the main cation components were Mg2+, Ca2+, Na+, and K+, the anion components were HCO3−, Cl−, and SO42−. A measure of 89% of the groundwater samples in this area were freshwater, the HCO3− were mainly dolomite, calcite, and gypsum dissolved precipitation resulted. Na+ and Cl− came from the dissolution of halite. Most of the groundwater was of the SO4·Cl-Ca·Mg type, accounting for 61.1%. The main ion chemistry of the shallow groundwater in this area is controlled by rock weathering, and pyrite oxidation is a significant factor affecting the SO42− concentration. These research results will help analyze the formation mechanism of chemical components and provide some basic data for the evolution of mine water in this area in the future.

Artificial intelligence in groundwater management: Innovations, challenges, and future prospects

The integration of Artificial Intelligence (AI) in groundwater management is a transformative stage, characterized by innovation and challenges. This research paper explores the multilayered application of AI in this field, dividing its contributions, addressing its associated challenges, and revealing the prospects of future potential. AI-driven innovations are designed to revolutionize groundwater management, providing precise predictive modeling, real-time monitoring, and data integration. However, these innovations face challenges such as interpretability issues, specialized technical expertise requirements, and limited data quality and quantity for effective AI model performance. In the future, AI holds significant promise in groundwater management. Advanced AI models can yield improved predictions of groundwater behavior, identify vulnerable areas prone to pollution and depletion, prompt proactive interventions, and foster collaborative platforms among scientists, policymakers, and local communities. Collaborative platforms driven by AI offer potential for synergistic engagement among scientists, policymakers, and local communities, collectively guiding groundwater resource management. Embracing AI's potential while addressing its challenges remains pivotal for sustainable and resilient groundwater management practices. By embracing AI's potential while addressing its challenges, the landscape of groundwater resource management will continue to evolve.

A Case Study of Groundwater Potential for Agricultural Sustainability in Ambala District, Haryana by using Geospatial Approach

This study focuses on analyzing the behaviour of groundwater in the Ambala District using a Geographic Information Systems (GIS) approach. The Ambala District, located in 30.2862° N, 76.9643° E faces challenges related to groundwater availability and sustainability due to increasing water demand and potential environmental impacts. The research integrates various datasets, including hydrogeological parameters, groundwater level measurements, land use/land cover data, and geological information specific to the Ambala District. These datasets are processed and analyzed using GIS tools, enabling the identification of spatial patterns, trends, and relationships associated with groundwater behaviour. The analysis encompasses key aspects such as groundwater recharge areas, flow direction, aquifer characteristics, and vulnerability to contamination. By overlaying different thematic layers and conducting spatial analysis, the study identifies areas with high potential for groundwater recharge, areas of groundwater flow convergence or divergence, and regions prone to contamination risks from anthropogenic activities.

Spatial Characterization of Shallow Structures in the Revell Batholith Integrating Seismic Imaging Techniques

The Revell Site, located in Northwestern Ontario within the Canadian Shield, is being assessed as a potential Deep Geological Repository (DGR) for Canada’s used nuclear fuel. Effective DGR establishment requires comprehensive subsurface assessment, particularly in evaluating structural stability, hydrogeological attributes, geological composition, and geochemical properties. Key among these considerations is understanding the three-dimensional characteristics of structural features to ensure the site’s suitability for long-term containment of radioactive materials. This case study focuses on imaging and characterizing structures within the predominantly intact biotite granodiorite-tonalite host rock at the Revell Site. Borehole data reveals these structures as mostly sub-horizontal mafic intrusions, with thicknesses of up to 3.5 m. They appear either as separate, discrete entities or in stacked configurations. Despite their limited thickness, most of these intrusions exhibit discernible attributes in surface seismic images due to their distinct physical properties. Some, however, exhibit velocity variations that decrease their overall reflectivity properties. An integrative approach employing surface seismic, Vertical Seismic Profiles (VSP), and borehole data facilitates the spatial identification of over 30 of these mafic structures. This comprehensive characterization not only lays the foundational framework for future discrete fracture network models but also provides important support for simulations related to fluid flow dynamics, groundwater behavior, contaminant dispersion, and heat transport mechanisms within the Revell Site. This study underscores the critical role of in-depth subsurface characterization in ensuring the secure, long-term management of radioactive materials in DGRs.

Lithology controls on the mixing behavior and discharge regime of thermal groundwater in the Bogexi geothermal field on Tibetan Plateau

Geothermal springs within the same geothermal system are naturally considered with similar output manifestation, but usually distinct. A low temperature geothermal spring group (Bogexi) on eastern Tibetan Plateau was investigated and compared with the boiling geothermal spring group (Rekeng) in the same fault zone to get insights into the reasons behind. The Bogexi geothermal springs have quite lower output temperature (25.0–65.3℃) than the boiling Rekeng geothermal springs (84.5–90.0℃). Although all these two geothermal spring groups have the same hydrochemical facies of HCO3-Na, the Bogexi geothermal springs present lower concentration of Na+ and trace elements. The geothermal waters of Bogexi were originated from the precipitation and glacier/snow meltwater of the eastern Haizi mountains with the recharge elevation of 4,400–4,700 m. These recharged waters infiltrate into the geothermal system that with the reservoir temperature of 160-180℃ and are heated by tectonic deformation heat in the depth of 3,100–3,400 m. Lithology determines the fissures development in the shallow and furtherly controls the mixing behaviors and discharge characteristics of geothermal springs in the discharge area. As a result, the thermal groundwaters of Bogexi are mixed with great quantity of shallow cycling cold water with the mixing proportion averaging at 73–76 % during the ascending process, leading to their lower output temperatures and distinct hydrochemical and isotopic features from the boiling Rekeng geothermal springs. A conceptual model was proposed to portray the genesis of low temperature geothermal springs in high temperature geothermal system. The recharged water percolates downward and is heated in the deep thermal reservoir. Heated waters are enriched of chemical elements during this process and then flow upwards under the driving of hydraulic pressure. While the lithology determines the circulation of cold water in the discharge area. Karst lithology, usually with developed fissures and channels, can provide more favorable conditions for cold water cycling in the shallow part than other lithology. This leads to considerable cold water mixed into the upward-flowing geothermal groundwater, and differs these geothermal springs from other ones in the same fault zone in output temperature and hydrochemcial features. This research can improve the understanding of formation mechanism of output discrepancies of various springs within one geothermal system.

Different groundwater behaviour in deep karst boreholes: the case of Jadro spring basin (Dinaric karst, Croatia)

The paper analyzes the data of groundwater level (GWL), groundwater temperature (TW), and electrical conductivity (EC) measurements in three deep piezometers (B1, B2, B3) in the Jadro spring basin, taken from October 2010 to December 2021. The variation of these parameters is analyzed at different time scales: annually, monthly, daily (24 hours), and hourly. They are compared with the data of the same parameters measured at the Jadro Spring. The analysis of the maximum observed rise and fall rates of the GWL showed that the piezometers were drilled in very different karst environments. Piezometer B1 is located in a karst matrix where the water flows predominantly in a diffuse laminar (slow-flow) regime. Piezometers B2 and B3 are located in a fault line where numerous large karst underground formations occur and rapid turbulent water flow takes place. The mean annual flows of the Jadro Spring strongly depend on the mean annual GWL-s in each of the piezometers. For much of the year (about 99%), the GWL in all three piezometers is more than 210 m below the ground surface. As the measuring sensors are located near the bottom of the piezometers, the groundwater temperature is almost stagnant. It is always at 12.5 ºC in piezometer B1 and behaves almost identically in piezometer B3. Water temperature is the highest in piezometer B2 and hovers around the average value of 13.5 ºC. At the Jadro Spring, the average water temperature is 12.95 ºC. The electrical conductivity values are the highest in piezometers B2 and B3, with an average of around 0.5 mS/cm. They are lower in piezometer B1, where they range around an average value of 0.465 mS/cm, while at the Jadro Spring, they vary from 0.40 mS/cm to 0.48 mS/cm, with an average value of 0.44 mS/cm. A distinct seasonal pattern in groundwater level behavior is evident across all piezometers. However, no discernible upward or downward trend is observed.

Assessment of Groundwater Response Scenarios for Surrounding Areas After Filling the Proposed Badush Dam Reservoir, Northern Iraq

In the current study, the depth of groundwater was detected in (39) wells in the banks surrounding Tigris River between Mosul and Badush dams, and then the maps of depth and level of groundwater were drawn. To predict the response of groundwater behavior in the banks of Badush reservoir in the strips adjacent to the river when starting the filling process, the lines of selected water levels in Badush dam were plotted on the map of groundwater equipotential lines to detect the areas confined between the water level in the reservoir and the same level for groundwater. It is assumed that these areas are affected by the bank storage; therefore, they are prone to leakage or geotechnical problems within the zone of engineering facilities foundations including Badush Dam itself, the regulatory dam and infrastructure projects. In the pre-storage stage, it is noted that the area of influence of the bank storage is very limited and does not exceed 2 km2 on each side of the river in the area very close to the dam. When the water level raises more at the beginning of the storage, the area of influence of the bank storage will extend towards the upstream close to the river meandering. The effect on the eastern bank (left) will be wider compared to the situation in the western bank (right) where the effect is limited. The eastern side is characterized by having a higher population density and more urban establishments; therefore, the foundations of these establishments will be more affected. The area affected by the bank storage continues to widen towards upstream with the increase in the level of the dam reservoir until the effect reaches the maximum limit and approaches the shoulders of the regulatory dam, when the water levels in Badush reservoir are more than 245 m above sea level (a. s. l.). The variation in the groundwater extension effect with the continuous or gradual filling of reservoir requires monitoring and caution during filling, for fear of affecting the geotechnical properties of the soil and rocks within the foundations zone, and thus affecting the stability of the two dams.

Experimental study on mix proportion optimization of anti-calcium dissolution shotcrete for tunnels based on response surface methodology

Aiming at the issue of crystallization and blockage of drainage system due to the massive calcium loss from the tunnel shotcrete, a self-designed tunnel seepage crystallization modelling system was developed. This system was produced in conjunction with the initial tunnel support shotcrete construction and drainage pipe installation, and is capable of simulating both the seepage process of groundwater in the shotcrete and the process of crystallization in the drainage pipe. Based on three different mechanisms of anti-crystallization, which include absorbing free calcium, reducing the porosity and increasing hydrophobicity, antialkali agent, nano-calcium carbonate, and silane were selected to test, respectively. Firstly, the suitable dosing ranges of these three external admixtures for resisting calcium loss in shotcrete were determined by single factor tests, which were 7%–11%, 4%–8%, and 0.3%–0.5%, respectively. Thereafter, the response surface method was employed to evaluate the interaction of antialkali agent, nano-calcium carbonate and silane on calcium loss in shotcrete, and to establish the relationship between them, and thus to determine the admixture ratio that can effectively reduce calcium loss crystallization in shotcrete, with the optimal admixture amounts of antialkali agent being 9.242%, nano-calcium carbonate 4.889% and silane 0.366%. Lastly, the reliability of the model test results was verified by the microscopic analysis, and the results showed that the total amount of calcium dissolution in the optimized group could be reduced by 75% compared with the blank control group, and was basically consistent with that derived from the response surface regression model, validating the high accuracy of the buildup response surface regression model. The present study can provide some ideas and references for reducing the seepage crystallization behavior of groundwater in the initial tunnel support shotcrete.

KEY ROLE OF FOSSIL SEAWATER IN NEOGENE SEDIMENTARY ROCKS FOR LANDSLIDE OCCURRENCES IN THE NORTHERN PART OF CENTRAL JAPAN

The south-western area of Niigata Prefecture has the highest landslide densities in Japan. Saline groundwater emerges from several landslides in this area and is an influential factor in the occurrence of these landslides. The geochemical approaches to groundwaters and application of the electromagnetic surveys for landslide slopes revealed the hydrogeological structure of the large-scale landslides which was located on the outlet of saline waters from deep reservoirs and landslide-prone area where wide zonal distributions of saline water at depths of more than 50–100 m and fresh water at depths of shallower than 50–100 m. It is most likely that the saline groundwater behavior emerging in large-scale landslides is controlled by injections of the geo-pressured saline waters from deep reservoirs. The injection of the geo-pressured waters into the landslide mass likely results in excess pore pressure, which is a possible cause of landslide occurrence. On the other hand, the shallow fresh groundwater is inferred to be meteoric water of origin that replaced the saline groundwater, which likely weakened the shear strength of bedrocks, resulting in landslides. Thus, pore saline water plays an important key role in the occurrence of landslides, both large-scale landslides with low frequency and common landslides.