Groundwater Zone Research Articles

Groundwater delineation for sustainable improvement and development aided by GIS, AHP, and MIF techniques

Exploration of groundwater is an integral part of viable resource growth for society, economy, and irrigation. However, uncontrolled utilization is mainly reported in urban and industries due to the increasing demand for water in semi-arid and arid regions of the world. In the background, groundwater demarcation for potential areas is vital in meeting necessary demand. The current study applied an integrated method comprising the analytical hierarchy process (AHP), multiple influence factors (MIF), combined with a linear regression curve and observatory well data for groundwater prospects mapping. Thematic maps such as flow direction, flow accumulation, elevation map, land use land cover, slope, soil texture, hill shade, geomorphology, normalized vegetation index, and groundwater depth map were generated utilizing remote sensing techniques. The relative weight of each parameter was estimated and then assigned to major and minor parameters. Potential zones for groundwater were classified into five classes, namely very good, good, moderate, poor, and very poor, based on AHP and MIF methods. A spatially explicit sensitivity and uncertainty analysis method to a GIS-based multi-criteria groundwater potential zone model is presented in this research. The study addressed a flaw in the way groundwater potential mapping results are typically presented in GIS-based multi-criteria decision analysis studies, where discrete class outputs are used without any assessment of their certainty with respect to variations in criteria weighting, which is one of the main contributors to output uncertainty. The study region is categorized based on inferred results as very poor, poor, marginal, and very good in potential ground quality 3.04 km2 is considered extremely poor, 3.33 km2 is considered poor, 64.42 km2 is considered very good, and 85.84 km2 is considered marginal zones, which shows reliable and potential implementation. The outcomes of AHP and MIF were validated by linear regression curve and actual water table in a study area. The study results help to formulate the potential demarcation of groundwater zones for future sustainable planning and development of groundwater sources. This study may be helpful to provide a cost-effective solution to water resources crises. The current study finding may be helpful for decision-makers and administrative professionals for sustainable management of groundwater resources for present and future demands.

Controlling Factors of Groundwater Salinization and Pollution in the Oasis Zone of the Cherchen River Basin of Xinjiang

Groundwater is a vital resource for local human life and production in the oasis zone of the Cherchen River Basin of Xinjiang. Understanding the controlling factors of groundwater salinization and pollution is of great significance for the sustainable utilization of groundwater resources and protection of the ecological environment in desert oasis areas. In light of this, a total of 36 single structure unconfined groundwater samples and 54 multi-layered structure unconfined and confined groundwater samples were collected from the oasis zone of the Cherchen River Basin and evaluated for the distribution characteristics and pollution status of major ions. Hydrogeochemical methods (e.g., Piper diagram, multivariate statistics, Gibbs model, and relationships among ions) were used to determine the main controlling factors of groundwater salinization and pollution. Differences in hydrogeochemical zonation were found from the single structure unconfined aquifers in sloping plains of piedmont areas to the multi-layered structure unconfined and confined aquifers in alluvial-proluvial plain areas, and Cl-Na (87.8%) was the main hydrochemical type in the groundwater of the study area. The quality of single structure unconfined groundwater was starkly better than that of the multi-layered unconfined and confined groundwater, which was mainly caused by Na+ (mean value of 9 969 mg·L-1), Cl- (13 687 mg·L-1), and SO42- (5 840 mg·L-1). Moreover, the natural hydrogeochemical process was the main reason for the deterioration of groundwater quality. The hydrochemistry was mainly controlled by the water-rock interaction and evaporation processes. The mineral dissolution of silicates and evaporites was an important source of chemical ions in the groundwater. Furthermore, the chemical weathering of evaporites combined with the processes of evaporation and cation exchange had a significant influence on the salinization of multi-layered unconfined and confined groundwater in alluvial-proluvial plain areas. In addition, synthetic fertilizers were the main pollution sources of NO3- in groundwater in the intensive agricultural zones.

Mapping Groundwater Potential (GWP) in the Al-Ahsa Oasis, Eastern Saudi Arabia Using Data-Driven GIS Techniques

Searching for new sources of water is becoming one of the most important aspects of scientific research, especially in areas prone to drought, like Saudi Arabia. The study aim was to delineate groundwater potential zones within the Oasis of Al-Ahsa, in Saudi Arabia’s eastern region, and to identify the optimum factors that control the availability of groundwater zones. This was achieved through examining the effect of ten environmental variables on groundwater recharge, namely: slope, topographic wetness index (TWI), land cover (LC), elevation, lineament density (Ld), drainage density (Dd), rainfall, geology, and soil texture. The variables were prepared from a variety of data sources, including spatial data (i.e., DEM and Landsat-8 image), in addition to other complementing data sources for appropriate parameters extraction. Two weighted overlay methods were used, namely the simple additive weight (SAW) as well as the optimum index factor (OIF) in order to categorize the optimal set of parameters for computing GWP and identifying its zones. Two GWP maps were obtained and validated through comparison with the locations of existing wells at GWP zones. The study findings have assured the cogency of the SAW map, where it was found that nearly 45–48% of the resultant zones were characterized as in the “moderate” class, whereas around 21–37% of the entire zones area were classified within the “high” class. The soil texture parameter was determined as being the most influencing parameter for GWP mapping followed by the “geology” parameter; however, the “lineament density” (Ld) was the least important factor. Furthermore, the OIF method has facilitated the identification of the optimal parameter combination for delineating groundwater potential (GWP) zones, which included “Ld”, “land cover”, and “TWI”. The study findings and methodology can serve as a potential model for other similar regions, supporting sustainable water resource management locally as well as globally.

Characterizing 226Ra and its daughters in coastal zone groundwater of a typical human-activity affected bay: occurrence, safety, and source evaluation.

Due to their extremely toxic properties, 226Ra and it daughters (222Rn, 210Pb, and 210Po) in drinking groundwater require monitoring. Recent studies have reported exceptionally high levels of natural 210Po (up to 10,000Bq/m3), 226Ra, and 222Rn isotopes in groundwater. This study aims to provide background data on 226Ra and its daughter radionuclides in the typical agricultural-industrial Dongshan Bay (DSB) before the construction of Zhangzhou Nuclear Power Plant (Zhangzhou NPP). The measurement results indicate that no abnormally high activities of 210Po and 210Pb were detected in the investigated wells. Strong positive correlations between 210Pb and 210Po, as well as between 222Rn and 210Pb activities, suggest that the origins of 210Pb and 210Po in groundwater are strongly influenced by the decay of the parent radionuclides 222Rn and 210Pb, respectively. In the DSB coastal zone groundwater, significant deficiencies of 210Po relative to 210Pb and 210Pb relative to 222Rn were observed, providing further evidence that 210Po and 210Pb are also effectively scavenged due to their geochemical properties (specifically particle affinity) within the groundwater-aquifer system. A systematic comparison among all relevant water bodies in the DSB revealed that the activity concentrations of 210Pb and 210Po in groundwater were the highest, except for rainwater. Based on the evaluation of 210Pb sources, the results imply that submarine groundwater discharge (SGD) is an important pathway for transferring radionuclides (such as 210Pb) from land to the nearshore marine environment, even though the study area has a lower 210Pb background groundwater. By considering all the 210Pb's sources in the DSB, we found low 210Pb background groundwater discharge still needs to be taken into account for small-scale bays. This is because SGD was calculated to be one of the most important 210Pb sources in the bay during observation season. Regardless of whether the system is in a normal state or a nuclear accident emergency state, greater attention should be paid to the groundwater discharge of radionuclides into the ocean.

GEOELECTRIC SIGNATURES FROM A LEACHATE PLUME MAPPED FROM A BASEMENT COMPLEX TERRAIN IN AKURE, NIGERIA

In this study, we investigated the implications of a leachate plume within an aquifer system, unravelling the intricate dynamics that govern contaminant transport and dispersion. An integrated approach of geophysical investigations is used to establish the impact of an open-waste disposal site around Aromed, in a part of Akure, in the Precambrian Basement Complex of Southwestern Nigeria. Investigations using eight (8) Vertical Electrical Sounding (VES) and Double-Dipole Resistivity Tomography (ERT) along two (2) traverses were conducted. The geoelectric interpretation and the inverted two-dimensional electrical resistivity tomography (ERT) images provided insights into the underlying geological composition, identifying three distinct units: the topsoil, the weathered column, and the fractured Basement/fresh Basement bedrock. The geoelectric tomography structures in the 2-D interpretation reveal that the dumpsite area exhibits low apparent resistivity estimated to be between 12 to 71 ohm-m in both the topsoil and the weathered column aquiferous zone. These values closely agree with results from the geoelectric sections, which range between 11 - 68 ohm-m, respectively. The relatively low apparent resistivity results are suggestive to be due to the presence of leachate’s chemical composition from the open waste disposal sites, which are suspected to be generated from the dissolution of ions of iron and other conductive minerals producing the leachate plume. The probable leachate depth of migration as revealed by the 2-D tomography structures varies from about <1 – > 14 m beneath the dumpsites. The leachate migration, which is structurally controlled, has a southward flow, majorly in the orientation with the observed structures. The subsurface depression-relief is also attributed to influence the direction of leachate flow. In conclusion, it is suggested that groundwater in the aquiferous zones in the vicinity of the dumpsites have entered a significant pollution level; hence water in the aquifer is not safe for consumption.

Remote sensing, GIS, and analytic hierarchy process-based delineation and sustainable management of potential groundwater zones: a case study of Jhargram district, West Bengal, India.

The present investigation delineates groundwater potential zones (GPZ) in the Jhargram district through an integrated approach employing analytical hierarchical process (AHP), remote sensing, and geographical information systems (GIS). Twelve parameters were utilized for GPZ analysis based on the Groundwater Potential Index, subsequent to multicollinearity testing. Classification of GPZ yielded five distinct categories: very poor, poor, moderate, good, and very good. Validation through receiver operating characteristics (ROC) and cross-validation with borewell yield data affirmed prediction accuracies of 78.4% and 84%, respectively. Spatial distribution analysis revealed that 30.39%, 30.86%, and 13.19% of the surveyed area fell within the poor, moderate, and good potentiality zones, respectively, whereas 15.86% and 9.69% were categorized as very poor and very good GPZs. Sensitivity analysis highlighted the significance of geology, elevation, geomorphology, slope, and lineament density as influencing parameters; elimination of any single parameter engendered significant alterations in the GPZ classification. The investigation culminated in the formulation of a block-wise sustainable groundwater management blueprint designed to inform policy initiatives.

Delineating hydro-geologically constrained groundwater zones in the Himalayan River basins of India through an innovative ensemble of hypsometric analysis and machine learning algorithms

Delineating hydro-geologically constrained groundwater zones in the Himalayan River basins of India through an innovative ensemble of hypsometric analysis and machine learning algorithms

Assessment of groundwater vulnerable zones using conventional and Fuzzy-AHP DRASTIC for Visakhapatnam district, India

Given the increasing impact of extreme climate change and the unpredictability of monsoons, the importance of preserving groundwater resources has never been more critical. Conducting a thorough groundwater vulnerability assessment enables one to pinpoint the zones most susceptible to contamination and take proactive measures to safeguard them. This paper is an attempt to enhance the conventional DRASTIC method by integrating Fuzzy Logic and Analytical Hierarchy Processes (FAHP) and applying this approach to the Visakhapatnam district. Spatial data for the seven parameters used in this study were created and analyzed using ArcGIS. The study determines and compares the groundwater vulnerability index using both the conventional DRASTIC method and the FAHP-DRASTIC method. Based on the index values, the groundwater zones in the study area have been classified into five categories: Very Low, Low, Medium, High, and Very High Vulnerability. Model validations were conducted using the ROC-AUC technique against Nitrate concentration. The results reveal that the FAHP-DRASTIC model, with an AUC of 0.92, is the most suitable model for the present study.

Geospatial Mapping of Groundwater Potentiality in Sooriyawewa Divisional Secretariat Division by Utilizing GIS

The dry zone of Sri Lanka is affected by drought conditions owing to a lack of rainfall. Hence, mapping the distribution of groundwater potential zones is vital for water management. The Hambantota district, which is in the dry zone is a severely afflicted area due to lack of rainfall, and Sooriyawewa divisional secretariat area faces water scarcity. Therefore, this study aims to map groundwater potentiality in the Sooriyawewa divisional secretariat division using a geographical information system. For this study, spatial interpolation techniques, weighted overlay analysis, georeferencing, and digitizing methods were used. In this study, the annual average rainfall, geology, geomorphology, drainage density, lineament density, land use land cover, slope, and soil maps were prepared, and integrating those maps, the final groundwater potential zones map was prepared by using ArcMap 10.5 software. The study found that there were no high-potential groundwater zones in the Sooriyawewa divisional secretariat division and it already consists of low and moderate ranges. Therefore, the final groundwater potential zone map was categorized as very low, low, and moderate. The Percentages of area Coverage according to classes as, very low 2%, low 91%, and moderate 7%. This study can be highly helpful in identifying the groundwater potential zones in the Sooriyawewa divisional secretariat division and in preventing water scarcity because identified groundwater potential zones can be used for effective water management and provide essential information to responsible authorities for decision-making. Furthermore, the identified potential zones can be used for rainwater harvesting and can be used properly for future consumption.

Unveiling groundwater potential zones as catalyst for multidimensional poverty reduction using analytical hierarchical process and geospatial decision support systems (S-DSS) approach in the semiarid region, Jigawa, Nigeria

Integrating agricultural production with the identification and use of groundwater resources has been shown to reduce multidimensional poverty in semi-arid regions. Poverty reduction and socioeconomic growth depend on sustainable water supply, especially in developing countries with limited rainy seasons. Poverty eradication is a top priority among the 17 Sustainable Development Goals (SDGs), and its reduction in the 21st century has led to significant advances in research. This study used remote sensing, geographic information system (GIS), and geospatial decision support system (S-DSS) approaches to uncover potential groundwater zones. The Analytic Hierarchy Process (AHP) integrates geospatial data to create a groundwater potential zone map and suggests the best land requirements for groundwater abstraction for poverty alleviation programs. The groundwater potential zone maps indicate that the majority of the region was in the high-potential zone, covering 59.75% of the total area, followed by a moderate-potential zone at 23.21%, an extremely high-potential zone at 14.6%, a low-potential zone at 2.44%, and an extremely low-potential zone at 0%. In addition, the study emphasizes the need for alternative water sources and infrastructure development in dry seasons in areas with fewer drainage systems and proposes measures such as rainwater harvesting structures and small reservoirs. Diversifying income sources by promoting alternative livelihoods can help reduce poverty and vulnerability to fluctuations in agricultural productivity. The integration of socioeconomic data into the S-DSS framework will provide a comprehensive understanding of the complex relationship between groundwater resources, poverty, and socioeconomic development, enabling informed decision-making in water resource management for poverty reduction initiatives and the achievement of the 2030 Agenda for Sustainable Development Goals.

Understanding the Deep Structure of the Essaouira Basin Using Gravity Data: Hydrogeological Inferences for a Semiarid Region in Central-Western Morocco

The Essaouira Basin, located in central western Morocco, faces a significant threat of water shortage due to both the substantially reduced rainfall caused by climate change and the continuously increasing demand for this essential resource. Groundwater resources are being increasingly exploited to meet the needs of the population, whether for agricultural or domestic purposes. Therefore, it has become necessary to intensify investigations across the entire basin, particularly through indirect methods such as geophysical techniques, to accurately delineate the productive zones. In this context, the present study was undertaken to investigate the deep structure of this basin with the aim of comprehending the functioning of its aquifer system. This study is based on the interpretation of gravity data covering the Essaouira Basin. In addition to their qualitative analysis, these data underwent a methodological approach involving transformations to extract meaningful insights. The observed anomalies were interpreted in terms of (i) thickness variations within the slightly folded sedimentary series of the basin; (ii) Paleozoic basement topography; and (iii) the presence of salt deposits. In fact, among the negative anomalies, some coincide with evaporitic deposits that are known either from the geological outcrops or the seismic surveys carried out in the Essaouira Basin within the framework of petroleum exploration programs, while others coincide with areas of increased thickness of sedimentary sequences. The latter include synclines and basement depressions, where the accumulation of groundwater tends to occur; as a result, they constitute suitable zones for the drilling of water extraction wells. Groundwater flows observed in some existing wells are consistent with this hypothesis. The results of the contact analysis approach implemented within the framework of the study reveals the Essaouira Basin is affected by a fault network whose main direction is parallel to the Atlantic margin (i.e., NNE–SSW). This implies that the extensional tectonic phase responsible for initiating the rifting of the Central Atlantic in the Triassic era has primarily impacted the structural configuration of this basin. This study demonstrates the strong potential of the gravity method as a tool to delineate the deep structure of sedimentary basins and to identify potentially productive groundwater zones. The final results will provide important support to decision makers in sustainable groundwater management, especially in vulnerable areas.

Computation of Groundwater Quality of Baramati with the help of Fuzzy Water Quality Index (FWQI)

One of the natural resources having the latent for home, agrarian, and engineering use is surface and groundwater. Due to humanoid and certain natural reasons, the eminence of the groundwater serving Baramati City and Tehsil has deteriorated. Agriculture is using more pesticides and fertilizer, therefore this supply is being affected. Municipal water pollution can be caused by “septic boilers”, “bathe sewage”, “polluted aquatic”, “improper discarded management”, “public excretion”, “improper waste structure”, “public sewage discharges”, and “unorganized solid waste disposal”. The current study will improve the accuracy of the water quality index for areas in Baramati Tehsil that are affected by industry and drinking water supplies. The groundwater zones were created using a weighted index overlay analysis, which assigned weights based on several classes of individual water quality metrics and drinking water standards. Based on few observations, fuzzy logic offers an effective and practical tool for categorizing drinking water quality. This study's objective is to provide a fuzzy logic-based water quality indicator for basin-wide reservoirs. For a weight-based fuzzy quality index, a minimum of 6 physico-chemicals are needed.

Field investigation of the transport and attenuation of fugitive methane in shallow groundwater around an oil and gas well with gas migration

‘Fugitive’ or ‘stray’ gas migration from deeper formations due to well bore integrity failure has prompted concern regarding environmental impacts. Unintended methane (CH4) migration can increase greenhouse gas emissions and affect groundwater quality in the critical zone. Although the CH4 transport in shallow aquifers has been investigated at experimental injection sites, no intensive groundwater studies have been published around an oil and gas well that has been leaking for a significant period of time. In this field study, groundwater samples were collected from sixteen groundwater monitoring wells (1.25 m below ground surface) installed around a suspended oil and gas well with decadal scale gas migration (estimated ~0.2 m3/day). Stray CH4 distribution and preferential pathways in the shallow groundwater zone were evaluated though high-resolution profiling of equivalent concentrations of hydrocarbon gases (C1-C6; >85 % CH4 at the study site) and bulk formation electrical conductivity to 6.0 m below ground surface. The highest dissolved CH4 concentration (0.074 mmol/L or 1.18 mg/L) in groundwater (1.25 m bgs) was observed immediately downgradient (1.25 m) of the oil and gas well head. Similarly, high-resolution profiling data also revealed the occurrence of relatively high CH4 concentrations in shallow groundwater along the groundwater flow direction and below fine-grained layers up to 10 m distance from the well head. Microbial DNA analysis from groundwater showed significant community shifts, with the highest relative abundance and diversity of methanotrophs observed in the vicinity of the oil and gas well. This study supports findings from experimental injection and laboratory studies, which also found that significant CH4 transport i) dominantly occurs in the groundwater flow direction, and ii) laterally as free phase below fine-grained layers. The occurrence of CH4 concentrations below saturation after more than two decades of gas migration suggests limited impacts have occurred in the shallow subsurface investigated.

The significance of morphometric analysis of Shimsha River, Karnataka, India to understand the hydrological and morphological characteristics

AbstractMorphometric analysis is crucial for advancing in various fields, including geomorphology, hydrology, environmental sciences, and geological studies. The objective of the present study is to understand the hydrological and morphological characteristics of the Shimsha River, which flows through the fluvial deltaic plain in the semiarid environment of Karnataka. Remote sensing and geographic information system have been used as mapping and efficient tools for drainage basin morphometry. The emphasis is laid on geological, geomorphological, hydrological, and fluvial features under linear, aerial, shape, relief, geometric, morphotectonic, and social morphometric parameters. The basin area is about 8741 km2, with a dendritic to subdendritic pattern. The sinuosity index is 1.6, which indicates meandering in nature. Areal parameters suggest that the drainage basin has a moderate surface permeability, homogenous lithology, run‐off, erodibility, low relief conditions, infiltration rate, and a well‐developed drainage network. Shape parameter indicates that the basin is subelongated with flatted peak flow and longer duration. Relief factor indicated low relief and intermediate stage of the incision rate. The river has an asymmetry factor is 38.65 and it shows that the channel has shifted southwest. The river shows a perfectly graded profile, with a considerable amount of incision and deposition along its profile showing tectonically unstable, based on the spatial distribution of the potential groundwater zone of about (5260 km2), other waterbody masks covered (285 km2). Standard visual interpretation techniques were applied to recognize and interpret the land use and land cover patterns. A basin rich in clay‐rich soil may lead to a massive flood. Essentially, physiographical and structural conditions controlled the stream order of the basin. The increase in the stream length ratio from lower to a higher order. That indicates a mature geomorphic stage of the study area. Rainfall and local lithology impact the development of segments of the stream.

Assessment of Groundwater Potential in a Mountainous Area Using Machine Learning and GIS, Rherhaya Basin, High Atlas, Morocco

Mountainous regions are vital for recharging aquifers in plain areas downstream, but understanding the geological, hydrogeological, and climatic factors is crucial to comprehend groundwater processes in these regions. Several parameters, including lithology, topography, secondary porosity, geological structures, and climatic conditions, affect the potential of groundwater in mountainous aquifers. Traditional groundwater modeling tools face several challenges in handling large amounts of real-time data, such as extracting useful features, quantifying uncertainty, and identifying links between different variables. Recent technological advances in artificial intelligence, particularly machine learning, provide solutions for hydrogeological research and applications. This paper focuses on modeling potential zones of groundwater sources using various methodologies based on GIS, spatial remote sensing, and machine learning. The study evaluated three models, Random Forest, Support Vector Machine, and Logistic Regression, in identifying potential groundwater zones in the Rherhaya watershed. More than 200 localized spring points were needed to ensure efficient model learning. The Support Vector Machine model demonstrated the highest performance during the 70/30% split, with a ROC-AUC of 84.4% for the test data. The study identified four critical conditioning factors of groundwater potentiality, including Topographic position index, River Distance, Valley Depth, and Plane Curvature. The models also highlighted the distance to rivers as a significant factor, particularly in the upstream portion of the watershed. The very low potentiality class occupied the largest area (over 32%), followed by low (between 24 and 29%), moderate (12–19%), high (10–14%), and very high (only 9–12%) classes. Only the Support Vector Machine model predicted that 12% of the catchment area had high potential for groundwater resources, indicating its superior performance in identifying high-potential zones. The results offer valuable insights that can aid decision-makers in effectively managing water resources in vulnerable areas.

Seasonal hydrology and gas transport in a composite cover on sulfide tailings

This study presents the field performance of a five-layer composite cover to mitigate acid mine drainage in legacy sulfide tailings in northern Ontario, Canada. Installed in 2008, this cover comprised sand, clay, geosynthetic clay liner, sand, and waste rock layers. To evaluate the effectiveness of the cover in reducing water and oxygen ingress, groundwater and vadose zone hydrological characterization, stable water isotope analysis, pore-gas measurements, oxygen flux calculations, and variably saturated flow modeling were conducted. The results indicate that the clay layer stayed nearly saturated in the spring, fall, and winter, but temporary desiccation occurred during the summer. Compared to uncovered tailings, the cover significantly lowered diffusive oxygen flux. In the summer, fall, and winter, the capillary barrier effect of the cover functioned effectively and inhibited percolation. Atmospheric pore-gas oxygen concentrations at one out of the three monitoring locations indicate potential cover imperfections that enabled oxygen transport into the tailings. In the spring and early summer, snowmelt infiltration resulted in percolation that compromised the capillary barrier effect, as well as lateral drainage. The resulting increase in water saturation in the cover limited oxygen transport. Despite potential cover imperfections, this composite cover reduced oxygen and water ingress a decade after installation.

Monitoring hydrological changes with satellite data: Spring thaw's effect on soil moisture and groundwater in seasonal Freezing-Thawing zones

Due to the dense vegetation coverage in mountainous areas and difficulties in field monitoring in mid-high-latitude freezing-thawing zones, satellite and remote sensing technologies can be used to monitor long-term global hydrological changes. This study uses multiple satellite data of snow water equivalent (SWE), soil moisture (SM), and groundwater storage anomaly (GWSA) to analyse their spatial–temporal changes in the seasonal freezing-thawing Tumen River Basin. Water transformation during the thawing period is determined through groundwater level fluctuations and correlation analysis methods; thus, the recharge effects of snowmelt and seasonally frozen soil thawing on soil moisture and groundwater are identified. The snow begins to melt in February, and snow water equivalent decreases gradually from upstream to downstream after reaching the peak. Furthermore, seasonally frozen soil melts gradually from March. Soil moisture downstream is higher than that in the upper and middle reaches. Additionally, the GWSA increases gradually in the thawing period, which is high in mountainous areas and low in plains. The Spearman correlation coefficient among ΔSWE, ΔSM, and ΔGWSA is more significant than 0.5 and dependent on altitude. With snow and frozen soil melting, vertical infiltration and meltwater percolation increase soil moisture and GWSA. This phenomenon is predominant at low altitudes (<600 m) and pore phreatic groundwater in the middle and lower reaches. However, snowmelt is the dominant factor in groundwater recharge at high-altitude upper reaches. For seasonal freezing-thawing zones, a close water transformation was observed between snow melting, soil water thawing, and groundwater in spring. Thus, the environmental and ecological impact of spring snowmelt and floods in freezing-thawing zones can be monitored using multi-source data.

Organic Solvent Contamination in Groundwater Around Natural Gas Plants

Alberta is a province that has vast deposits of natural gas. However, in its natural form it is considered sour in that it has impurities, i.e., it contains hydrogen sulphide (H2S), carbonyl sulfide (COS), carbon dioxide (CO2), mercaptans and organic sulphides. To enable the marketing of the natural gas these impurities must be removed using organic compounds and solvents. As a result of spills, leakage during processes, seepage from unlined storage ponds some of these solvents have contaminated groundwater around natural gas processing facilities. Remediation of the organic solvents is a difficult problem. To achieve an understanding of the processes involved in their degradation, a hydrogeochemical assessment of a site can be done using existing data from the site to track the development of groundwater redox zones across the different hydrostratigraphic units (HSU). This is relevant because the oxidation is hypothesized to have contributed to the biodegradation of the compounds. The objective of this global assessment is to assign a groundwater redox zone for each sample, with special emphasis placed on defining the oxidative groundwater zone (OGZ) due to its relevance to biodegradation. Ideally, the oxic groundwater zone would be defined based on the concentration of molecular oxygen (i.e., dissolved ) in groundwater (McMahon and Chapelle 2008). However, molecular oxygen, normally measured as ‘dissolved oxygen’, was not routinely measured as a field parameter in this study and therefore was unavailable to define the OGZ. The scheme adopted considers the concentrations of terminal electron acceptors (TEA) present in groundwater and measured in commonly measured parameters including oxygen, nitrate, and sulphate and dissolved metals (manganese and iron). These TEA's are consumed under progressively more reducing conditions after oxygen reduction is complete in the order: nitrate reduction, manganese reduction, iron reduction, sulphate reduction, and finally carbonate reduction (one form of methanogenesis). The results show that redox zonation is heterogeneously distributed across the site, both within and between HSUs. Multiple lines of hydrogeochemical evidence support buffered aerobic biodegradation at the site.

Identifying groundwater prospect zones through earth observation techniques in Bilate watershed, Rift Valley Lakes Basin, Ethiopia

ABSTRACT Groundwater is one of the most valuable natural resources gifted to mankind, especially in surface water-scarce locations. Most parts of Ethiopia dependent on the amenity for common needs, irrigation, etc. The lack of a scientific approach to its exploitation and management makes the resource underutilized. Therefore, Remote sensing (RS) and Geographic information systems (GIS) were utilized to decipher potential groundwater zones (PGWZ) existing in the Bilate watershed of the nation to economize, speed up and technicalize the system. The ground truth of the results obtained was verified to confirm the reliability of the techniques used. Through RS, optical and microwave data were obtained, while GIS was helpful in collecting information on water points mapping and 2D resistivity survey in locating the aquifers. In particular, resistivity studies revealed both pyroclastic and rhyolite intrusions that act as water barriers and the basaltic and ignimbrite rocks that favour aquifer affluence. During the process of identification and quantification of PGWZ in the watershed, the analytical hierarchy process (AHP), weighted linear combination (WLC), and digital elevation model (DEM) were employed in thematic layer formation, reclassification, overlay analysis and map production. As a result, five PGWZ having very high (19.8%), high (35.3%), moderate (22.6%), low (19.3%), and very low (2.9%) prospects were identified. Similarly, over 75% of the area was moderate to high category in PGWZ. The accuracy of the qualitative groundwater inventory was 92.64 per cent. Thus, combining high-resolution optical/microwave data and GPS information with the AHP model has ascertained the accuracy of the PGWZ identified. So ultimately, the present work lays the foundation for the use of advanced spatial techniques in finding natural resources useful for the welfare of the nation and its populace.

Hydrostratigraphy and hydrogeophysical studies to delineate fresh and saline aquifer boundaries in Lesser Cholistan of Pakistan.

The differentiation of saline water and fresh water interfaces is a key objective in ground water exploration and management. Bahawalpur is the twelfth biggest metropolitan area of Pakistan situated in south Punjab near the bank of River Sutlej and lies at 29°59'55" N latitude and 73°15'12" E longitude at an elevation of 521 ft AMSL in the Cholistan area close to the Thar abandon. The study area comprised of Lesser Cholistan experiencing acute shortage of water for inhabitants and livestock as well. The occurrence of fresh water is also challenging because of high salinity in groundwater. The present study is intended to identify hotspots of fresh groundwater zones. To achieve the goal, vertical electrical resistivity and borehole data are used to mark fresh and saline interfaces in groundwater. To achieve the results 230 vertical electric sounding were performed in the study area. A total of 3 to 5 geo-electric layers are identified with modeling along with the processing and interpretation of resistivity data. In the study area, resistivity values are classified as very high (>230 Ω-m), high (230-100 Ω-m), medium (100-40 Ω-m), low (40-20 Ω-m) and very low (<20 Ω-m). Borehole data is used to interpret subsurface lithologies and to calibrate the modeled resistivity curves. The electric resistivity data indicates that thick layers of Quaternary sediments is present in the subsurface that is primarily composed of clay, silt, sand, gravels and some kanker. Inversion technique is applied to generate 2D subsurface resistivity maps to delineate fresh and saline water zones. The generated 2D resistivity maps at variable depth above and below water table and formation resistivity maps are successfully utilized to differentiate fresh and saline water zones. The identification of a saline water aquifer within sediments rich in clay was made possible by the observation of very low resistivity measurements in the southern region. Conversely, the detection of relatively high resistivity values, coupled with the presence of sand and gravel deposits in the northern section of the lesser Cholistan area, provided compelling evidence of the existence of fresh groundwater. These findings have significant implications for the management of water resources in the region, as they provide valuable insights into the distribution and availability of groundwater resources for future use.