Groundwater Reservoir Research Articles

Simulation study on the clogging process of suspended matter in recharge of anti-filtration recharge well

ABSTRACT Anti-filtration recharge wells are a class of recharge facilities in groundwater reservoirs with their own anti-filtration function, and aquifer clogging is a key issue in recharge. In this paper, the process of recharging groundwater by rainfall flood water recharge from an anti-filtration recharge well was simulated by indoor sand column test, and the change of permeability coefficient, turbidity at the outlet, and the distribution of suspended particulate matter at the end of the experiment were measured and computed, so as to analyze and study the effect of filtration in anti-filtration recharge wells and carry out the contrast test with ordinary recharge wells without a recharge pool. Compared with ordinary recharge wells, the anti-filter layer in the recharge pool of anti-filtration recharge wells can largely remove suspended matter in recharge water and intercept suspended matter at the surface, thus preventing aquifer clogging, and it is recommended that the anti-filter layer should be cleaned up and replaced regularly according to the experimental results, and this study provides a reference for the practical application of anti-filtration recharge wells.

Characteristics and formation of natural fractures in a silica-rich chalk, Coniacian Arnager Limestone Formation, Bornholm, Denmark.

Natural fractures are abundant and important components in many carbonate sedimentary rocks globally. In hydrocarbon and groundwater reservoirs of carbonate rocks they can form connected networks and thereby influence the permeability and f luid flow significantly. Outcrop studies of fractured carbonate rocks can provide an essential understanding of 3-dimensional fracture networks, thereby aiding in understanding fracture patterns and connectivity in subsurface carbonate reservoirs. The Arnager Limestone Formation is a naturally fractured silica-rich chalk of Coniacian age exposed in a coastal cliff on the island of Bornholm in the Baltic Sea (Denmark). This study examines the natural fractures in the Arnager Limestone Formation from a structural and geomechanical perspective. The Arnager Limestone Formation forms one, 12–20 m thick, main rock mechanical unit; bedding planes acts as weak interfaces and divides it into near-identical, cm- to dm-thick rock mechanical subuits. Flat-lying (horizontal) or low-angle dipping bedding-parallel fractures are intersected by two near-vertical or steeply dipping fracture systems, a major N–S-trending system and a less prominent W–E-trending fracture system. Rock mechanical analysis of the tensile strength and elastic moduli provides the foundation for discussing maximum burial depth of the Arnager Limestone Formation. The tensile strength gives information on the bedding-parallel fractures, which can have formed due to stress relief during uplift and erosion, possible accentuated by glacial processes. The near-vertical fracture sets are interpreted to have formed in response to tectonic movements.

A Composite Approach for Evaluating Operational Cloud Seeding Effect in Stratus Clouds

Robust water management is in intense demand in many water scarcity areas, such as arid and semi-arid regions in the world. As part of the regional water management strategy, rain enhancement is vital to replenish groundwater reservoirs, and the key challenge is how to assess its effectiveness. Some recent weather modification experiments attained cloud seeding effect through advanced in situ measurement coupled with accurate numerical simulation. However, there is still a lack of an objective and scientific approach to quantitatively evaluate the rain enhancement effect, especially for many non-randomized operational cloud seeding activities in China. In this study, we proposed a composite evaluation approach by analyzing two operational aircraft cloud seeding cases in stratus clouds in Shaanxi, China. By calculating the aircraft cloud seeding agent plumes, the target areas (as well as the control areas) of cloud seeding were dynamically and roughly determined. Physical properties, such as radar reflectivity and precipitation, were individually quantified in these areas. The cloud seeding effect was then evaluated by calculating the difference in parameter variation between target and control areas. This approach can be applied to qualitative analysis in a single aircraft cloud seeding operation and can also provide quantitative statistical results from multiple cloud seeding cases. We found that the average precipitation enhancement percentage of 18 operational aircraft cloud seeding cases is ~4.84%. Note that the homogeneity hypothesis of the seeding cloud, the error in the calculation of the target area, and the selection of control areas are the major uncertainties likely in the evaluation of the cloud seeding effect by this approach.

A 2‐Billion‐Year History of Water‐Alteration in Terra Sirenum, Mars: Volcanism's Influence on Aluminum Clay Formation and Chemically Distinct Waters Forming Sulfates and Chlorides Into the Amazonian

AbstractTerra Sirenum, a region of Noachian highlands southwest of the Tharsis volcanic complex, is unique in the number, proximity, and diversity of orbital detections of secondary minerals, as the sole region found to date hosting large‐scale deposits of all of Mars' major salts (chlorides, sulfates, carbonates) as well as diverse hydrated silicates. We combine mineralogical information, high‐resolution imagery, and elevation models to investigate the geologic context of these secondary minerals to understand the sources of water and ions for each type of deposit and their spatial/temporal relationships. Carbonates, where present, are part of Noachian basement rocks exposed through cratering and do not appear associated with evaporative sequences. Numerous small detections of the acid sulfate minerals alunite and jarosite mirror the dominant clay cation in the localities they are found—Al phyllosilicates and Fe phyllosilicates, respectively—suggesting in situ formation. We interpret a previously discovered kaolinite‐rich unit overlying Fe/Mg clays across northeast Terra Sirenum as remnants of a widespread ash unit rather than a pedogenic weathering sequence. Sulfate and chloride detections are decoupled, with sulfates in topographic lows likely precipitated from volcanism‐associated groundwaters, while chloride detections are consistent with surface water runoff, in some instances clearly post‐dating volcanic units capping sulfate detections. Volcanic resurfacing of craters in the region is progressively younger from west to east, and crater statistics‐based ages indicate localized sulfate‐ and chloride‐forming processes continue to occur from ∼3.5 to ∼1.4 Ga. We hypothesize that their decoupling points to disconnected, episodic surface and groundwater reservoirs, perhaps separated by a permafrost layer.

Epikarst Controls of Runoff Composition in Subterranean Stream After Rainstorm Events

ABSTRACTEpikarst plays a critical role in karst water circulation, however, its studies have often been limited to small springs or basins, ignoring its importance in larger, highly karstified subterranean streams. This study focused on the Longlingong (LLG) subterranean stream system, where the discharge and electrical conductivity (EC) of the subterranean stream outlet for 2.5 years, and found that 85% of all rainstorm events monitored during this period showed a pattern of increasing and then decreasing EC. High‐resolution hydrochemistry monitoring was conducted at the outlet during a rainstorm event when this response pattern occurred. Simultaneously, epikarst water (EW), saturated zone fissure karst water (FW), and surface water (PW) from this system were collected as three recharge sources for hydrochemical analyses based on the results of the field investigations, and end‐member mixing analyses were performed using the EMMA‐MIX model. These combined methods can accurately characterise the response of the subterranean stream system to rainstorm events, assess the contribution and response of individual recharge sources throughout the rainstorm, and reveal the mechanisms involved. The results indicate that the increase in EC is primarily driven by changes in HCO3− concentration resulting from the rapid discharge of EW through sinkholes and shafts. EW contributes 28.7% of the rain‐induced subterranean stream runoff, exceeding FW. The epikarst exhibits a rapid response to rainstorms, as evidenced by a remarkable 681% increase in EW discharge following a rainstorm event. Flood peaks in the subterranean stream are mainly composed of PW (44%) and EW (43.6%). This study highlights the key role of the epikarst as a karst groundwater reservoir. The sensitivity of the epikarst to rainstorms, particularly its role in facilitating rapid piston‐like migration of EW during initial runoff, highlights its significant influence on discharge and hydrochemistry. This research contributes to a deeper understanding of the function of epikarst within highly karstified subterranean streams.

Causes of the Groundwater Levels Rise in the Absheron Peninsula and the Ways of its Regulation

In connection with the growth of Baku city and its adjacent regions located in the Absheron Peninsula, this territory is the most densely populated part of our republic. The waste from industrial enterprises and oil and gas fields, a significant part of which is also located within the Peninsula, has a negative influence on the ecological situation of the studied area. This article provides an overview of the hydrogeological conditions of various areas of the object under study and identifies changes in the level of groundwater in these areas while establishing the reasons for its rise. Physical and chemical analyses of water samples taken from drilled wells and dug wells throughout the region were carried out. The reasons for the increase in the level of underground water were established, which lead to flooding, swamping, and recurrent salinization of the soil in the Absheron Peninsula. Measures and recommendations were developed to restore the ecological balance of the study area. In addition, groundwater, phreatimetric data, and water reservoir strikes in cities, villages, and settlements located on the peninsula were studied. The physico-chemical composition of underground waters and their mineralization levels were studied in laboratory conditions. The groundwater levels in drilled and dug wells across the peninsula were established and compared with data from historical records and literature. The studies conducted allowed for the evaluation of the suitability of groundwater for various national and economic uses. It has been established that, simultaneously with natural factors, anthropogenic factors have had a significant influence on the rise in the level of groundwater, including the absence of central sewage and drainage systems, the discharge of water from industrial enterprises, and household water, among others. To eliminate the environmental emergency, it is recommended to carry out priority temporary measures in some areas of the Absheron Peninsula at the initial stage.

Chemical hydrogeodynamics of the Kultuk groundwater reservoir vs. paragenetically related large earthquakes in the central Baikal Rift System, Siberia

Chemical hydrogeodynamics of the Kultuk groundwater reservoir vs. paragenetically related large earthquakes in the central Baikal Rift System, Siberia

Artificial recharge initiatives in India: Challenges and future scope

Artificial recharge of aquifers is regarded as a fundamental supply-side strategy in India to address the prevalent issue of groundwater over-exploitation. Rainwater harvesting and artificial recharge are often implemented as cohesive sets of interventions because of the significant collateral benefits of rainwater harvesting. Central and state governments have implemented various schemes that incorporate rainwater harvesting and artificial recharge. Several studies are underway to investigate the optimal selection of construction sites, structural types, and designs based on local hydrogeology, groundwater flow patterns, terrain conditions, and water demand. These investigations aimed to assess the impact of these factors on resource replenishment and water quality enhancement. Studies have been conducted to determine the extent to which such initiatives yield socio-economic advantages. The discourse has encompassed crucial concerns, such as the accessibility of source water for recharge, conflicts between upstream and downstream stakeholders, and the increasing recognition of various demand-side measures for the sustainable administration of groundwater reservoirs. The paper highlights that there has been a rise in the number of studies regarding artificial recharge post-2020. Overall, this paper showcases the challenges for the implementation of artificial recharge structures with special focus on aspects such as site suitability, water quality concerns, operational problems and governance. The study also sheds light on the future scope of artificial recharge for the sustainable use of groundwater resources. More studies should be performed considering large-scale implications of artificial recharge structures considering resilience towards climate change and water quality and quality concerns.

Offshore freshened groundwater reservoirs controlled by submarine faults with a complex dependency on antecedent hydrogeological conditions

Offshore Freshened Groundwater (OFG) reservoirs are gaining attention, as evidence suggests they are more prevalent worldwide than previously thought. OFG systems are generally classified as either passive, a relic of ancient, lower sea levels, or as active, with an onshore-offshore hydrogeologic connection and associated discharge offshore. Previous studies on the mechanisms of OFG were conducted in various hydrogeologic settings, but the role of faults remains understudied. Based on geologic data, we apply hydrogeologic modeling of a faulted submarine confined aquifer in the Levant basin (eastern Mediterranean), to study the impact of faults on OFG. We find that faults that are close to the coastline and within the brackish zone that would have developed without a fault control the offshore salinities regardless of initial conditions. The influence of distal faults, in contrast, depends on antecedent conditions. When initial salinities are such that the distal fault lies in the fresh part of the aquifer, the saline wedge migrates landward toward the fault with sea-level rise, and the fault dictates the steady-state salinity distribution. If the fault is initially within the saline part of the aquifer, freshwater never reaches the fault, likely due to the density-driven flow barrier that the underlying saline wedge generates. These findings suggest a new mode of OFG in which the same geologic system can be either active or passive depending on the hydrologic history. This should be considered in future studies of OFG systems, the functioning of which has implications for marine ecosystems, seafloor geomorphology, and coastal water resources.

Exploring waterborne viruses in groundwater: Quantification and Virome characterization via passive sampling and targeted enrichment sequencing

Aquifers, which provide drinking water for nearly half the world's population, face significant challenges from microbial contamination, particularly from waterborne viruses such as human adenovirus (HAdV), norovirus (NoV) and enterovirus (EV). This study, conducted as part of the UPWATER project, investigates the sources of urban groundwater contamination using viral passive sampling (VPS) and target enrichment sequencing (TES). We assessed the abundance of eight viral pathogens (HAdV, EV, NoV genogroup I and II, rotavirus, influenza A virus, hepatitis E virus and SARS-CoV-2) and investigated the virome diversity of groundwater in the aquifer of the Besòs River Delta in Catalonia. Over a period of 7 months, we collected 114 samples from the aquifer using nylon and nitrocellulose membranes to adsorb viruses over a 10-day period. Human faecal contamination was detected in nearly 50 % of the groundwater samples, with mean HAdV total counts ranging from 1.23E+02 to 3.66E+03 GC, and occasional detections of EV and NoV GI and GII. In addition, deep sequencing revealed a diverse virome in the aquifer, with detection of human pathogens, including adenovirus, astrovirus, calicivirus, enterovirus, herpesvirus, papillomavirus and rotavirus. Time-integrated sampling using VPS increases the likelihood of virus detection and, when combined with TES, can provide a deeper understanding of virus prevalence in this important water compartment. This approach is expected to streamline long-term monitoring efforts and enable small communities or water managers with limited resources to effectively manage their groundwater reservoirs.

Postsynthetically Modified Cationic, Robust MOF Featuring Selective Separation of Carboxylate-Containing Pharmaceutical Drugs from Water at Neutral pH: Elucidation of the Adsorption Mechanism by Theory and Experiments.

The escalating levels of hazardous pharmaceutical contaminants, specifically nonsteroidal anti-inflammatory drugs (NSAIDs), in groundwater reservoir surfaces and surface waterway systems have prompted substantial scientific interest regarding their potential deleterious effects on both aquatic ecosystems and human health. Extraction of those pollutants from wastewater is quite challenging. Hence, the development of economic, sustainable, and scalable techniques for capturing and removing those pollutants is crucial to ensure water safety. Herein, we demonstrate a physicochemically stable, reusable, porous Hf(IV)-based cationic metal-organic framework (MOF), namely, 1'@MeCl for the aqueous phase adsorption-based removal of NSAIDs (diclofenac, naproxen, ibuprofen) from the wastewater environment. The highly positively charged surface of the 1'@MeCl MOF enables it to selectively extract more than 99% of diclofenac, naproxen, and ibuprofen contaminants within less than 30 s. With fast adsorption kinetics, very high adsorption capacities (Qe) were achieved at neutral pH for diclofenac (482.9 mg/g), naproxen (295.9 mg/g), and ibuprofen (219.5 mg/g). Moreover, the influence of changes in pH and coexisting anions on the adsorption property of the 1'@MeCl MOF was studied. Furthermore, the adsorption efficiency of 1'@MeCl in different real water environments was ensured by performing diclofenac, naproxen, and ibuprofen adsorption from tap, river, and lake water. Moreover, a 1'@MeCl-anchored cellulose acetate-chitosan membrane was developed successfully to demonstrate the membrane-based extraction of diclofenac, naproxen, and ibuprofen from contaminated water. Furthermore, a molecular-level mechanistic study was performed through experimental and computational study to propose the plausible adsorption mechanisms for diclofenac, naproxen, and ibuprofen over the surface of 1'@MeCl.

Study of pollutant transport under linear sorption in a groundwater reservoir

Abstract Pollutant dispersion in a porous medium can be modelled mathematically to forecast its concentration distribution profile. The governing equation of pollutant transport is modelled as a partial differential equation. Effects of sorption, zero-order production rate and first-order decay rate on pollutant transport are incorporated in the present study. The temporarily dependent pulse-type input source decaying exponentially is assumed at the origin of the domain. The solution of the proposed transport equation is derived by Laplace transform method for the respective time split domain. Matlab algorithm is developed to illustrate the obtained analytical solutions graphically for various hydrological input data. The pollutant distribution profiles in the medium are obtained for different times and porosities. The pollutant transport nature is examined for various forms of velocity flow pattern in presence and absence of input source. Also, the derived solution is compared graphically under special case with the existing solution and found the results with good agreement.

Groundwater quality evaluation of the weathering mantle in crystalline basement aquifer system, southern Brazil.

Groundwater is the main source of water for more than 2 billion people worldwide. In southern Brazil, the Crystalline Basement Aquifer System is composed of strategic groundwater reservoirs. Groundwater is mostly taken from shallow wells, and it is often used without any treatment, which poses a risk to public health. The present study aims to evaluate shallow groundwater quality and the geochemistry of shallow and deep groundwater located in the municipality of Canguçu, southern Brazil. The physicochemical and microbiological parameters of groundwater samples collected from shallow wells were monitored and analyzed using ANOVA variance analysis and water quality index (CCME WQI) approaches. Also, the results were compared with secondary data from deep wells. The monitored shallow wells had thermotolerant coliforms, Escherichia coli, pH, potassium, manganese, iron, and nitrate in disagreement with the guidelines of the World Health Organization. Moreover, variance analysis showed that the parameters temperature, dissolved oxygen, pH, chloride, and magnesium were the most influenced by seasonal variations. According to the CCME WQI, most samples had good quality (60%), 28% had fair quality, and 12% had poor quality. In addition, the field campaigns with higher precipitation rates also presented fair quality. Therefore, most of the shallow groundwater quality is affected by surface pollutants from the urban area, aggravated in rainy periods. Whereas deep groundwater is influenced by geochemistry mechanisms. The results revealed the risk of water consumption for public health and the urgent need for better maintenance of these wells and water treatment implementation.

Extent of gross underestimation of precipitation in India

Abstract. The underestimation of precipitation (UoP) in the hilly and mountainous parts of South Asia is estimated by some studies to be as large as the observed precipitation (P). However, UoP has been analyzed to only a limited extent across India. To help bridge this gap, watershed-scale UoP was analyzed using various P datasets within a water imbalance analysis. Among these P datasets, the often-used Indian Meteorological Department (IMD) dataset is of primary interest. The gross UoP was identified by analyzing the extent of the imbalance in the annual water budget of watersheds corresponding to 242 river gauging stations for which quality-controlled data on catchment boundaries and streamflow are available. The water year (WY)-based volume of observed annual P was compared against the observed annual streamflow (R) and the satellite-based actual evapotranspiration (ET). Across many watersheds of both Northern and Peninsular India, spurious water imbalance scenarios (P≤R or P≪R+ET) were realized. It is shown that the management of water, such as groundwater extraction, reservoir storage and water diversion, is generally minimal compared to the annual P in such watersheds. It is also shown that annual changes in terrestrial water storage are minimal compared to the annual P in such watersheds. Assuming that data on R (and, to a lesser extent, ET) are reliable, it is concluded that UoP is very likely the cause of this imbalance. Inter-watershed groundwater flow (IGF) is assumed to be negligible. While the effect of IGF on R is unknown, examples are provided which show that IGF is unlikely to be the cause of the observed imbalance in certain watersheds. All 12 of the P datasets analyzed here suffer from UoP, but the extent of the UoP varies by dataset and region. The reanalysis-based datasets ERA5-Land and IMDAA are less affected by UoP than the IMD dataset. Based on the 30-year period of WY 1985–2014, P for the whole of India could be as much as 19 % (ERA5-Land) to 37 % (IMDAA) higher than that from the IMD, with substantial variability within years and river basins. The actual magnitude of UoP is speculated to be even greater. Moreover, trends seen in the IMD's P are not always present in ERA5-Land and IMDAA. Studies using IMD should exercise caution since UoP could lead to the misrepresentation of water budgets and long-term trends. Limitations of this study are discussed.

Conventional water resources associated with climate change in the Southeast Mediterranean and the Middle East countries

Conventional water sources in the Southeast Mediterranean and the Middle East play a crucial role in driving the socio-economic progress of the region. This study aims to address the uncertainties, discrepancies, and gaps in knowledge regarding how to combat the climate crisis and extreme weather events impacting traditional water sources. These sources encompass rivers, lakes, reservoirs, and groundwater reservoirs that are vital for agriculture, industry, and daily household needs. The availability and upkeep of water resources in this area are influenced by factors like climate change, population growth, and competing demands from different sectors. The methodology involved an extensive review of research literature curetted from a wide array of international scientific studies and reports, drawing data from sources such as PubMed, EBSCO, Medline, EMBASE, CINAHL, Scopus, Web of Science, Science Direct, Google Scholar, and UNESCO, WHO databases. The findings underscore the importance of traditional water sources in these regions, underscoring their significance for agricultural, industrial, and domestic applications. The accessibility of water resources varies among nations, with some grappling with water scarcity issues. This research delves into the condition of traditional water sources in the Southeast Mediterranean and the Middle East, shining a spotlight on concerns like water scarcity, pollution, and governance, offering valuable insights into these critical resources.

Monitoring of water volume in a porous reservoir using seismic data: A 3D simulation study

A potential framework to estimate the volume of water stored in a porous storage reservoir from seismic data is neural networks. In this study, the man-made groundwater reservoir is modeled as a coupled poroviscoelastic–viscoelastic medium, and the underlying wave propagation problem is solved using a three-dimensional discontinuous Galerkin method coupled with an Adams–Bashforth time stepping scheme. The wave problem solver is used to generate databases for the neural network-based machine learning model to estimate the water volume. In the numerical examples, we investigate a deconvolution-based approach to normalize the effect from the source wavelet in addition to the network's tolerance for noise levels. We also apply the SHapley Additive exPlanations method to obtain greater insight into which part of the input data contributes the most to the water volume estimation. The numerical results demonstrate the capacity of the fully connected neural network to estimate the amount of water stored in the porous storage reservoir.

An integrated approach for sewage diversion: Case of the Huayuan mine, Hunan Province, China

Environment protection is a core priority for many governments in this century. Most environmental problems have diverse causes: emission of greenhouse gases from fossil fuels, resource depletion, or intense mining activities such as the Huayuan manganese mine. The positioning of mining factories and water treatment stations impacts the surrounding groundwater reservoir. As the mine expands, the environmental impact also increases, and the previous plan based on monitoring wastewater leakage has become inappropriate. Therefore, to solve this issue, a new study is required to understand the lateral resistivity distribution underground and to define a new station location for water treatment and divert the sewage to that station. In this study, the audio-frequency magnetotelluric method is used. Surveys of two long lines that cross the mining area to its boundaries are carried out. Data are robustly processed and inverted. Based on the inverted models, in addition to the geologic information, drilling inspections, and solid waste distributions map, the integrated interpretation develops two sites on the top of impermeable layers, which constitute a buffer point between the unsafe (high concentration of pollutants) and the safe zones in the northwestern part of the mine. From the resistivity distribution combined with the water quality analysis, a relationship between the fault structures reveals an interconnected conductive zone (CZ) in the southeastern part. As the main channels for water circulating underground, these CZs delineate the main groundwater reservoir with a clastic aquifer layer. However, close to factories, the water from faults contains solid wastes, thereby making the groundwater in that zone nonpotable, unlike the safety zone located in the northwestern part. This workflow can become a field guide to improve the environment of mines and the deployment of hydrogeologic drilling in a safe area.

The Potential for Restoring the Activity of Oxidoreductases and Hydrolases in Soil Contaminated with Petroleum Products Using Perlite and Dolomite

The research focused on assessing the response of oxidoreductases (dehydrogenases and catalase) and hydrolases (urease, acid phosphatase, alkaline phosphatase, arylsulfatase, and β-glucosidase) to diesel oil (DO) and gasoline (G) contamination of soils subjected to phytoremediation with Zea mays. The activity of enzymes constitutes one of the fundamental mechanisms for the removal of contaminants from soil, which have the potential to contaminate not only the soil but also groundwater and water reservoirs. Additionally, correlations between enzyme activity and the basic physicochemical properties of the soil were determined. The interaction of perlite and dolomite with soil enzymes and the cultivated plant was also tested. The study was carried out in a pot experiment, where soil contaminated with DO or G was artificially treated at doses of 0, 8 cm3, and 16 cm3 kg−1. Perlite and dolomite were applied for remediation at doses of 0 and 10 g kg−1 of soil. Zea mays was found to respond to the tested pollutant with a reduction in biomass. DO affected the growth of this plant more than G. DO reduced the yield of aerial parts by 86% and G by 74%. The negative effects of these pollutants on the growth and development of Zea mays were mitigated by both perlite and dolomite. DO exerted greater pressure than G on the activity of oxidoreductases and hydrolases, as well as on the physicochemical properties of the soil. DO enhanced the activity of oxidoreductases and most hydrolases, whereas G inhibited them. The implementation of dolomite intensified the activity of all enzymes, except AcP (acid phosphatase) and Glu (ß-glucosidase), in soil contaminated with DO and G, and also improved its physicochemical properties. Perlite induced less significant effects than dolomite on soil enzymes and the physicochemical properties of the soil.

Effects of the 2021 La Palma volcanic eruption on groundwater hydrochemistry: Geochemical modelling of endogenous CO2 release to surface reservoirs, water-rock interaction and influence of thermal and seawater

Volcanic islands face unique challenges in protecting and managing their water resources due to their small size, limited freshwater availability, and vulnerability to natural hazards. The recent 2021 eruption of the Tajogaite volcano on La Palma Island in the Canary Islands, Spain, raised concerns regarding the potential impact on groundwater hydrochemistry. This work aimed to characterize and model the processes that lead to the measured hydrochemical impacts in the groundwater of La Palma as a consequence of the volcanic eruption. The study involved conducting three groundwater sampling campaigns during the eruption, and six after the eruption ceased. A total of 15 monitored points, including piezometers, wells, water galleries, and the main gully collector of the island, all relatively close (2 to15 km) to the erupted volcano, were sampled for the analysis of major solutes and SiO2. Unpublished hydrochemical data previous to the eruption were provided by the local water management authorities of La Palma (CIALP) and the Geological Survey of Spain (IGME). Statistical analyses were performed to assess the differences in groundwater composition before, during, and after the eruption, and a Principal Component Analysis (PCA) mixing model was calculated. Three compositional extreme waters were defined as end members in the system: (1) a high SiO2 computed thermal end member; (2) a low salinity computed fresh groundwater; (3) and seawater. The results of the mixing model showed two main events of maximum mixing ratios in the fresh groundwater reservoirs of La Palma after the eruption; the first one of seawater in July 2022, and the next one of thermal fluids in December 2022. This water mixing during and after the eruption, together with a volcanic CO2 input to the reservoirs, led to significant increases in the concentrations of Na, Ca, SiO2 and SO4 in fresh groundwater, as well as a drop in pH. The significance of these findings relies in improving our understanding of the effects of volcanic eruptions on groundwater, emphasizing the necessity for frequent monitoring and evaluation, given the scarcity and vulnerability of groundwater resources in volcanic islands.

UNDERSTANDING GROUNDWATER DEPLETION IN INDIA: ASSESSING RISK THRESHOLDS AND ANALYSING CAUSATIVE FACTORS

Although hidden below the Earth’s surface, groundwater makes up 99% of Earth’s liquid fresh water and plays an important role in the water cycle. Rivers, lakes and wetlands are surface manifestations of groundwater, exchanging flow with the groundwater reservoir that feeds them when they need water and takes some of their flow when surface water is in excess. Groundwater also controls many features on the Earth’s surface. The depth of the water table is partly responsible for different plant species occupying different positions along the slopes from hill to valley, as only the drought-tolerant plants can live on dry hillsides and water-tolerant plants live near streams. Dissolution of carbonate rocks by flowing groundwater creates caves and sinkholes. In desert environments, groundwater discharge forms oases, which provide habitats for animals and plants. Groundwater provides drinking water entirely or in part for as much as 50% of the global population and accounts for 43% of all water used for irrigation. Worldwide, 2.5 billion people depend solely on groundwater resources to satisfy their basic daily water needs. The Earth’s population of nearly 8 billion in 2020 is expected to reach 11 billion by 2100. Humans will have to learn to produce sufficient food without destroying the soil, water and climate. This has been called the greatest challenge humanity has faced. Sustainable management of groundwater is at the heart of the solution. Scientific understanding and proper management of groundwater is essential because groundwater can alleviate the problem if we seek its responsible use and replenishment. Modern scientific measurements show that many of the major aquifers (groundwater reservoirs) of the world are being depleted. Such depletion can lead to a decrease in stream flow, drying of springs or wetlands, loss of vegetation, water-level declines in wells, and land subsidence. Yet another threat to groundwater is pollution resulting from human activity, generating chemicals and wastes that have leaked into the subsurface. Pollution degrades the quality of groundwater and poses a threat to human and ecological health. As the human population grows, more demand will be placed on groundwater, a vast, but finite, resource. The need for understanding our groundwater systems and thoughtfully managing them within the constraints of the hydrologic cycle is greater than ever. In this paper, our primary objective is to examine the history of the water crisis in India, critical risk tipping points and delve into the analysis of how we arrived at the current state of groundwater depletion, exploring the specific conditions and factors that have led us here. Furthermore, we will project the trajectory of this situation and assess where we are headed. Most importantly, we will outline the vision for the future that we aim to craft, considering the well-being of the next generations and the sustainability of India's groundwater resources.