Increase In Groundwater Salinity Research Articles

Mechanism controlling groundwater chemistry in the hyper-arid basin with intermittent river flow: insights from long-term observations (2001–2023) in the lower Heihe River, Northwest China

The geochemical processes of groundwater in arid regions are generally influenced by both natural hydrological processes and human activities. However, impacts of water-rock interactions on groundwater recharge via hydrological processes, controlled by both intermittent river water flow and groundwater withdrawals, is still poorly understood. In this study, 327 groundwater chemistry datasets collected from the upper, middle (including Gobi and riparian zones), and lower regions of the Ejina Delta in Northwest China from 2001 to 2023 were analyzed. Our results revealed that the total dissolved solids (TDS) concentration of groundwater in Ejina Delta ranged from approximately 881.5 ± 331.6 mg/L in the upper regions to 1,953.6 ± 1,208.5 mg/L in the lower regions, with an increasing trend observed. Ecological water conveyance (EWC), recharging aquifer through intermittent river water flow, resulted in a decrease in TDS concentrations from 2001 to 2023 mainly in the upper region. While irrigation notably affected groundwater chemistry in the lower region, resulting in a substantial increase in groundwater salinity. Groundwater chemistry in the Middle Gobi region remained relatively stable over the study period. Generally, the hydrochemical composition shifted from the Na-Mg-SO4-HCO3 and Na-Mg-Ca-SO4-HCO3 types in the upper region to Na-Mg-SO4-HCO3 and Na-Mg-SO4-Cl types in the lower region, with Na-SO4-Cl predominant in the Middle Gobi. These shifts were likely be attributed to the interplay of water-rock interactions, coupled with evaporation-crystallization processes. Inverse modeling using PHREEQC revealed that in the upper-middle region, primary water-rock interactions involved calcite dissolution and the precipitation of dolomite, gypsum, halite, and sylvite salts, as well as cation exchange reactions (2NaX+Ca2+→CaX2+2Na+). In contrast, the hydrogeological system in the middle-lower region exhibited an opposite pattern of water-rock interactions. Overall, ecological water conveyance partially facilitated water-rock interactions during lateral groundwater flow, while irrigation disrupted the natural hydrogeochemical equilibrium, involving halite dissolution and opposite cation exchange reactions compared to other regions.

The Effect of Saltwater Stress on the Performance of Cherry Tomatoes

Rising sea levels and saltwater intrusion in aquifers pose significant challenges for South Florida agriculture, leading to increased groundwater salinity and potential crop losses. Utilizing salttolerant crop species presents a potential solution for saline soils and regions with active saltwater intrusion. However, the effects of soil salinization through groundwater alone remains less studied. This research investigates the impact of short-term, below-ground saltwater stress on the growth, survival, and overall health of commonly grown cherry tomatoes (Solanum lycopersicum). The objectives of the study are to: 1) determine the impact of saline groundwater on tomato plant health and 2) compare the nutrient content of soil and tomato plant tissue exposed to varying concentrations of saline water. Established cherry tomato plants were exposed to varying concentrations of NaCl solution, simulating saltwater intrusion into groundwater. Over 28 days, plant height, leaf chlorophyll levels, and disease occurrences were monitored. It was found that the NaCl treatments did not significantly affect cherry tomato performance under the parameters of height, chlorophyll levels, or leaf nutrition when compared to the control group. This study suggests that cherry tomatoes can tolerate short-term exposure to NaCl in groundwater. Further exploration of more intense salt stress conditions from groundwater could be beneficial for utilizing this crop in areas with saline soils or polluted groundwater. Identification of salt-tolerant cherry tomato varieties can provide alternative crop options for non-arable land affected by high soil salinity.

A numerical modelling approach to investigate the fate of brine reject of farm scale desalination plants on groundwater aquifers in arid environments

Farm-scale desalination units are gaining popularity for agricultural irrigation in arid countries, such as Kuwait to meet freshwater demands. However, less attention has been given to the management of environmentally hazardous brine reject water they produce. In this study we investigated the fate of brine water produced by the inland desalination units on the underlying aquifers using numerical modelling and field investigations. The methodology involved developing groundwater flow and solute transport models using Flex VMF-SEAWAT to simulate the movement of reject brine. The field investigations included collecting 150 water samples and conducting pumping tests on newly drilled wells. This numerical simulation considered advection, dispersion, and adsorption processes with variable groundwater density following rigorous validation and calibration of the developed numerical models. The results show that the RO reject brine will significantly increase groundwater salinity, exceeding 10,000 mg/L when accounting for advection, dispersion, and adsorption processes. The sustainable yield of the aquifer, with a salinity of <10,000 mg/L, averages 500 Mm3 but is expected to be depleted within 16 years with the current extraction rate. The resulting hydraulic properties are favourable with K about 100 m/d, T > 1000 m2/day, and Sy just >0.1. The adopted values for dispersivity and adsorption coefficients for chloride and sulphate salts in the aquifer were 10 m and 1 × 10−7 [mg/L]−1 respectively. Chemical and numerical analyses indicate a mixing ratio between the reject brine and groundwater in the study area of approximately 10 %. Uncontrolled groundwater extraction, combined with the surface disposal of RO reject brine, has led to a significant decline in groundwater levels and an increase in the salinity. The adsorption ratio of simulated brine plume was 13 %. The authors recommend to dispose the RO reject water in a safe location or transfer it to the nearest wastewater treatment plant for proper treatment and reuse.

Application of stable isotope of water and a Bayesian isotope mixing model (SIMMR) in groundwater studies: a case study of the Granvillebrook and Kingtom dumpsites.

The increase in groundwater salinity of the two major dumpsites in Sierra Leone has been a major concern for stakeholders. Therefore, this study employed geochemical and stable water isotope analyses to investigate the factors controlling groundwater salinity. The proportional sources of the groundwaters were also evaluated using the Bayesian isotope mixing model. The geochemical analysis showed that the groundwaterchemistry in the Granvillebrook dumpsite is controlled by water-rock interaction and evaporation while that of the Kingtom is dominated by water-rock interaction and precipitation. The biplot of deuterium (δ2H) versus oxygen (δ18O) composition relative to the global meteoric water line confirms that the groundwaters of the study areas are of meteoric origin. The linear plot of electrical conductivity versus δ18O depicts that mineralization is the major factor impacting the groundwater salinity in the study areas. The stable isotope mixing model in R (SIMMR) suggests that 96.5% of the groundwaters in the study areas are recharged by precipitation while only 3.5% originated from surface water. The SIMMR model also depicts that groundwaters in the Granvillebrook dumpsite have been bridged by leachate (33.0%) and domestic wastewater (15.2%) while for the Kingtom dumpsite, 13% and 21.5% are contaminated by leachate and domestic wastewaters. Contrary to other previous studies, this research confirms the feasibility of using the Bayesian isotope mixing model to quantify the factors influencing groundwater salinity.

Dynamics of Spatiotemporal Variation of Groundwater Arsenic Due to Salt-Leaching Irrigation and Saline-Alkali Land

Determining the link between the evolution of salt-leaching irrigation, saline-alkali land, and groundwater arsenic (As) is essential to prevent groundwater arsenic pollution and implement appropriate soil salinization control projects. The objectives of our study were to explore the spatiotemporal correlation of saline-alkali land and salt-leaching irrigation with groundwater As in the Hetao Plain. Therefore, groundwater As concentrations during Period I (2006–2010) and Period II (2016–2020) were collected by historical data and chemical measurements. Salt-leaching irrigation area and saline-alkali land area in Period I and Period II were extracted through remote sensing data. With the increase of the salt-leaching irrigation area level (SLIAL) and saline-alkali land area level (SALAL), the variation trend in groundwater As concentration slightly fluctuated, with an increase in the SLIAL at the low SALAL, which may be because short-term flooding may not considerably enhance As mobilization. Lower groundwater As concentrations appeared in regions with higher SLIAL and lower SALAL. A larger saline-alkali land area (higher SALAL) increased the groundwater As concentration. The path analysis model confirmed that salt-leaching irrigation may increase groundwater salinity to affect groundwater As levels and to decrease the saline-alkali land area. From Periods I to II, the difference in path analysis results may imply that the decrease in the saline-alkali land area may have influenced As mobilization due to competitive adsorption caused by the increase in total dissolved solids (TDS) in groundwater. Our results provide new insights for the impacts of saline-alkali land and salt-leaching irrigation both on groundwater As concentration and the geochemical processes of As enrichment in arid and semi-arid areas with more serious salinization.

A multi-isotopic evaluation of groundwater in a rapidly developing area and implications for water management in hyper-arid regions

Management of water resources in hyper-arid areas faces vital challenges in a global climate change context. Consequently, understanding the effects on groundwater sources can help mitigating the problem of water scarcity and the negative impact of human intervention on the environment. A case study area in the hyper-arid climate of the United Arab Emirates, was tackled here with the focus on applying stable isotopes as tools for evaluating groundwater sources and quality assessment. The results of major ions indicate variable increase in groundwater salinity moving away from Al Hajar Mountains recharge areas to the discharge areas (Arabian Gulf coast). The data of stable isotopes (δ18OH2O, δ2HH2O, δ18ONO3, δ15NNO3, δ18OSO4, δ34SSO4, δ11B) suggest impact of paleo-groundwater in the abstractions of the wells nearest to the coast. Nitrate isotopes indicate farming activities sources that can be masked due to the contribution from the nitrate-poor paleo-groundwater. Nitrate reduction processes are expected near to the recharge front. Sulphate and boron isotopes further suggest that influence of ancient evaporite dissolution in salinization. Management efforts should be focused on the diffuse sources of quality mitigations that can be vital in fingerprinting local and regional (transboundary) effects.

Modelling Shallow Groundwater Evaporation Rates from a Large Tank Experiment

A large tank (1.4 m x 4.0 m x 1.3 m) filled with medium-coarse sand was employed to measure evaporation rates from shallow groundwater at controlled laboratory conditions, to determine drivers and mechanisms. To monitor the groundwater level drawdown 12 piezometers were installed in a semi regular grid and equipped with high precision water level, temperature, and electrical conductivity (EC) probes. In each piezometer, 6 micro sampling ports were installed every 10 cm to capture vertical salinity gradients. Moreover, the soil water content, temperature and EC were measured in the unsaturated zone using TDR probes placed at 5, 20 and 40 cm depth. The monitoring started in February 2020 and lasted for 4 months until the groundwater drawdown became residual. To model the groundwater heads, temperature, and salinity variations SEAWAT 4.0 was employed. The calibrated model was then used to obtain the unknown parameters, such as: maximum evaporation rates (1.5-4.4 mm/d), extinction depth (0.90 m), mineral dissolution (5.0e-9 g/d) and evaporation concentration (0.35 g/L). Despite the drawdown was uniformly distributed, the increase of groundwater salinity was rather uneven, while the temperature increase mimicked the atmospheric temperature increase. The initial groundwater salinity and the small changes in the evaporation rate controlled the evapoconcentration process in groundwater, while the effective porosity was the most sensitive parameter. This study demonstrates that shallow groundwater evaporation from sandy soils can produce homogeneous water table drawdown but appreciable differences in the distribution of groundwater salinity.

A review: saltwater intrusion in North Africa's coastal areas-current state and future challenges.

North Africa coastline extends on 8955 km from Mauritania to Egypt. These areas continue to experience population and economic growth. North Africa coastal aquifers were exposed to an increase in groundwater salinity and seawater intrusion, which may contribute to economic crisis as a result of freshwater resources crisis. This work aims to explore the status and a holistic comprehending review of saltwater intrusion extent in the region and future challenges. Results on seawater intrusion in North Africa, from published papers and grey literature, show a several efforts have been made in understanding this phenomenon and developing management strategies in Egypt, Libya, Tunisia, Algeria, Morocco, and Mauritania. The most method used is geochemical data and statistical analysis. Some studies linked geochemical data with geophysical techniques, geographical information system (GIS), and GALDIT index. Seawater intrusion varies from one country to another according to the aquifer hydrogeological settings, abstraction rates and aquifer morphology, climate change, urban expansion, and economic development. North Africa countries, such as Libya and Mauritania, need, for instance, more expertise and experience on the part of local researchers. The challenge of inadequate data and a need for a more robust data inventory was stressed. This paper recommends developing and building scientific capabilities in regional and international partnerships, and adopting rational water governance for sustainable development.

Susceptibility mapping of groundwater salinity using machine learning models.

Increasing groundwater salinity has recently raised severe environmental and health concerns around the world. Advancement of the novel methods for spatial salinity modeling and prediction would be essential for effective management of the resources and planning mitigation policies. The current research presents the application of machine learning (ML) models in groundwater salinity mapping based on the dichotomous predictions. The groundwater salinity is predicted using the essential factors (i.e., identified by the simulated annealing feature selection methodology) through k-fold cross-validation methodology. Six ML models, namely, flexible discriminant analysis (FDA), mixture discriminant analysis (MAD), boosted regression tree (BRT), multivariate adaptive regression spline (MARS), random forest (RF), support vector machine (SVM), were employed to groundwater salinity mapping. The results of the modeling indicated that the SVM model had superior performance than other models. Variables of soil order, groundwater withdrawal, precipitation, land use, and elevation had the most contribute to groundwater salinity mapping. Results highlighted that the southern parts of the region and some parts in the north, northeast, and west have a high groundwater salinity, in which these areas are mostly matched with soil order of Entisols, bareland areas, and low elevations.

Use of isotopes techniques to reveal the origin of water salinity in an arid region of Central-Western Argentina

Groundwater is a strategic and vital resource for agriculture and oil production in the arid region of Carrizal sub-basin (CSB) in Argentina. Increasing groundwater salinity in some areas has created legal conflicts between water users over the source of the salinity. A multidisciplinary approach using hydrogeological, chemical and isotope tools were used to evaluate the source of groundwater salinity in CSB. The Mendoza River is the main source of recharge to the CSB aquifer. Groundwater and surface water from the recharge area near the Mendoza River to the discharge area of the CSB were analyzed for the study. The groundwater salinity varies between ~1000 μS/cm in the north (recharge area) to ~4000 μS/cm in the central region. There is a clear correlation between high level of nitrate and the high salinity spots in the aquifer. These data and the stable isotopes data suggests the source of groundwater salinity is associated with irrigation return flows from the agriculture areas. This is fully supported by the carbon isotopes data that showed clearly the input of carbon from the irrigated agriculture areas in the aquifer. No evidence was found about the role of the oil industry in the salinization of groundwater in the study area. However, a groundwater of different origin than the recharge from the Mendoza River was found down-gradient of the oil field which needs further investigation. The results of this study have implications for improving water management in agriculture areas in arid environments where water resources are under significant pressure due to more demand by an increase in population and agriculture activities under a scenario of a cycle of droughts and climate change.

Groundwater level observations in 250,000 coastal US wells reveal scope of potential seawater intrusion

Seawater intrusion into coastal aquifers can increase groundwater salinity beyond potable levels, endangering access to freshwater for millions of people. Seawater intrusion is particularly likely where water tables lie below sea level, but can also arise from groundwater pumping in some coastal aquifers with water tables above sea level. Nevertheless, no nation-wide, observation-based assessment of the scope of potential seawater intrusion exists. Here we compile and analyze ~250,000 coastal groundwater-level observations made since the year 2000 in the contiguous United States. We show that the majority of observed groundwater levels lie below sea level along more than 15% of the contiguous coastline. We conclude that landward hydraulic gradients characterize a substantial fraction of the East Coast (>18%) and Gulf Coast (>17%), and also parts of the West Coast where groundwater pumping is high. Sea level rise, coastal land subsidence, and increasing water demands will exacerbate the threat of seawater intrusion.

Utilizing Bamboo Cavity as an Appropriate Technology for Shallow Groundwater Conversion

Since the early 1970s, many farmers on the west coast of Indonesia have used groundwater to irrigate their agricultural land. Groundwater used is mainly done for rice, corn, and other secondary crops. As a result, the groundwater level in the area has experienced significant degradation and has also been followed by an increase in groundwater salinity. The government's suggestion to make artificial recharge with composter pipes or with "biopori" technology is considered difficult for farmers since they cannot afford to buy PVC pipes as their main ingredient. The challenge gave birth to our innovation to utilize local materials in the form of bamboo for artificial infiltration tools, which we call "bamboo-cavity." The three advantages of filling with "bamboo-cavity" are: (1) the ingredients are cheap and easy to obtain in the area of people's agriculture; (2) pollution-free because the material is without chemicals; and (3) easy to install because there is no need for soil drilling, where the bamboo is directly put in a hand hummer. This initial research was carried out with two objectives, namely: (1) Finding out the effect of "cavities" on the recovery of degraded groundwater; and (2) Knowing the effect of the number of inflection points on the rate of recovery of groundwater. The research was carried out by applying nine variations in the number of infiltration points, on agricultural land with topsoil characteristics that have low permeability. The results of the study provide an overview of the effectiveness of cavities as a means of enhancing, namely: (1) the effect of the number of cavities on increasing groundwater levels is very significant. The results of field observations found that the total increase in groundwater level in wells with the formation of 8 cavities reached 75%, compared to the increase in groundwater level in the control wells and the more installed cavities, the higher the increase in groundwater that occurs; (2) The test wells with the highest value of additive effectiveness are wells with a number of cavities between 56 and 64 points of infiltration, i.e., the recharge effectiveness reaches 3.74.

Assessing Aquifer Water Level and Salinity for a Managed Artificial Recharge Site Using Reclaimed Water

This study was carried out to examine the impact of an artificial recharge site on groundwater level and salinity using treated domestic wastewater for the Korba aquifer (north eastern Tunisia). The site is located in a semi-arid region affected by seawater intrusion, inducing an increase in groundwater salinity. Investigation of the subsurface enabled the identification of suitable areas for aquifer recharge mainly composed of sand formations. Groundwater flow and solute transport models (MODFLOW and MT3DMS) were then setup and calibrated for steady and transient states from 1971 to 2005 and used to assess the impact of the artificial recharge site. Results showed that artificial recharge, with a rate of 1500 m3/day and a salinity of 3.3 g/L, could produce a recovery in groundwater level by up to 2.7 m and a reduction in groundwater salinity by as much as 5.7 g/L over an extended simulation period. Groundwater monitoring for 2007–2014, used for model validation, allowed one to confirm that the effective recharge, reaching the water table, is less than the planned values.

Possible factors for increasing water salinity in an embanked coastal island in the southwest Bengal Delta of Bangladesh

Increasing water salinity in coastal areas is a concern for the coastal environment. Increased salinity is affecting water quality, freshwater availability, and water-related ecosystems in the southwest coastal region of the Bengal Delta. The study used a synergies and robust approach to assess the possible factors for increasing water salinity in an embanked coastal island in the southwest Bengal Delta. The hydrochemical analysis revealed that surface and groundwater are enriching with Na+ and Cl− concentration, also controlling by seawater through the ion exchange mechanism (Ca2+ and Mg2+ replacing by Na+, and Cl−), mixing stage of water solution (freshwater-saltwater), and anthropogenic salt contamination by human activities (e.g., saltwater shrimp cultivation and excessive irrigation). Piper diagram showed that river water is occupying at the mixing stage of solution, where pond and groundwater are occupying at seawater (saline) zone. The water quality index showed that surface water is not fresh anymore and unsuitable for drinking purposes. The isotope analyses exposed the presence of strong precipitation variance in the study area. Cluster observation analysis showed a strong correlation between Na+, Cl−, and TDS (similarity is 97% to 99%). The remote sensing application illustrated that high salinity zones are in the northern part, and groundwater salinity is higher (7.5 to 8 ppt) in the northern part of polder 32. The salinity of both groundwater and surface water showed a positive correlation with land surface temperature and potential evapotranspiration. The study exposed four responding factors for increasing groundwater salinity in this region, which are - regional surface geological settings, hydrological settings, hydraulic head gradient, and human activities. A conceptual model illustrated the presence of lateral recharge of saltwater from the surrounding tidal rivers to the groundwater.

The effects of climate change and groundwater salinity on farmers’ income risk

Abstract Climate change, in addition to reducing rainfall and increasing temperature, has led to a decline in water quality and increased groundwater salinity in Iran. These factors have a negative effect on crop yields. Therefore, the assessment of the effects of climate change and groundwater salinity on agricultural production is necessary. Hence, the object of this study was to investigate the effects of temperature, precipitation and groundwater salinity changes on farmer’s income risk, water shadow price and economic, social and environmental indicators in Qazvin region. To this purpose, the sensitivity of crop yield to temperature, precipitation and groundwater salinity was estimated by using Response-Yield function and General Maximum Entropy method, then, these variables were predicted for 2030, 2040 and 2050 horizon. In the following, using the Target-Motad-PMP Model, the effects of climate and groundwater quality variables on economic, social and environmental indicators were simulated. Finally, using the multi-criteria decision-making approach, the most appropriate scenario of climate change was identified in Qazvin region. The results showed that climate change and groundwater salinity increasing have negative effects on income risk and water shadow prices. In the most pessimistic scenario, revenue risk and shadow prices will decrease by 11.2 and 20.3% respectively by 2050 horizon. The results showed that the environmental index with 43.8% is the priority of the farmers compared to the economic and social indicators. Also, among the environmental indicators, the water consumption sub-index is the most important in this region with 29.5%. Based on the TOPSIS ranking technique, the most appropriate climate scenario is the B1 scenario. It is suggested that B1 scenario be put on the agenda for adaptation to the climate change phenomenon in this region.

Quantitative Study on the Changes of Karst Groundwater Level and Hydrochemistry in Jinci Spring Catchment, Shanxi, China

Since Jinci spring ceased to flow on April 30, 1994, it has never been reflowed, which seriously affects the sustainable utilization of karst groundwater. The purpose of this paper is to provide the basis for the reflow of Jinci spring and the sustainable protection for karst groundwater. Based on the long-term monitoring data from 1994 to 2014, this paper accurately quantifies the changes in the quantity and hydrochemistry of karst groundwater resources. By means of the Mann–Kendall trend test method, this paper analyzes the variation trends of karst groundwater level, EC, and SO42− in Jinci spring catchment. Monitoring data show that the groundwater level in the karst aquifer declined by 2.32 m from 1994 to 2008, which is equivalent to a loss of 3.3 Mm3 in aquifer storage, while the groundwater level rose by 17.67 m from 2009 to 2014, which constitutes a gain of 25.2 Mm3. The results indicate that (1) karst groundwater level showed a rising trend, which was mainly controlled by the rainfall, exploitation of karst groundwater, and the Fenhe River leakage; (2) groundwater salinity varied greatly and showed an increasing trend: increasing order of 47.83% for the six major ions, 37.52% for EC, and 3.34% for pH; (3) the increase of groundwater salinity is governed by the increase in rainfall salinity, the increase in groundwater runoff time, the recharge of the Fenhe River to groundwater, the increase of sewage in spring catchment, and the ease of solubility of carbonate rocks. The results of this study are of great significance for predicting the groundwater level and salinity of karst aquifer and ensuring the safety of drinking water in Jinci spring catchment.

Sustainability of brackish groundwater utilization from the Eocene Aquifer for oil exploration operations in central Kuwait

The Kuwait Oil Company currently pumps about 10 Mm3/yr from one of its well fields in central Kuwait (Eocene Aquifer) and plans to increase this rate to 30 Mm3/yr to meet its water demand. The objective of this study is to investigate the sustainability of brackish groundwater resources for oil operations in the mentioned well field in a way to identify the consequences of increasing the pumping rates on groundwater levels and groundwater salinity. A suitable methodology to assess the sustainability of brackish groundwater utilization has been developed based on pumping tests in addition to flow and salinity numerical modeling. Extensive hydrogeological and salinity field investigations were also conducted. The results show that pumping rate should not be increased above 20 Mm3/yr in the aquifer of the study, otherwise a sharp decline in groundwater levels and a significant increase in groundwater salinity will occur. The results of the pumping tests show that the hydraulic properties of the Eocene Aquifer can support regional utilization of the aquifer, but any additional pumping wells should be located within a wider area than the current well field. The salinity variation analysis shows that a mixing process between brackish and saline water is taking place.

Subsurface investigation of seawater intrusion and its impact to the domestic water fulfillment in Pekalongan City, Indonesia

The increasing of population growth in the Coastal Area of Pekalongan City has caused serious problem to the domestic water supply. It was getting worst due to seawater intrusion phenomenon. This research aims to investigate seawater intrusion using geophysical method and observe its impact to the domestic water fulfillment. Three sections of 2D resistivity were run approximately 250 meters’perpendicular from the coast line. The resistivity data were processed using RES2DINV software. We also did aninterview to 90 householdsto find out the impact of seawater intrusion in domestic water usage. The result showed that seawater has intruded up to 800 meters from the coast (represent with very low resistivity, <5 Ωm) and increased groundwater salinity significantly to a depth of 13 meters.Nearly everyhousehold in the North part of Pekalongan City could not use groundwater to fulfill their domestic neededdue to the massive seawatercontamination. They had a big dependency of water supply from the government drinking water company even with poor quality. Preventive mitigation action is really urgent to be done in order to reduce the future risk of seawater intrusion in the coastal area.

Fly Ash Impact from Thermal Power Stations on the Environment

Dumps of thermal power plants in Russia occupy significant areas. They are a source of pollution of air and water basins, contribute to increasing groundwater salinity and falling into the environment of radioactive elements. The work presents the results of experiments to identify the physical and chemical properties and toxicological effect of low-calcium ash from five thermal power plants on the environment.

Influences of groundwater extraction on flow dynamics and arsenic levels in the western Hetao Basin, Inner Mongolia, China

Data on spatiotemporal variations in groundwater levels are crucial for understanding arsenic (As) behavior and dynamics in groundwater systems. Little is known about the influences of groundwater extraction on the transport and mobilization of As in the Hetao Basin, Inner Mongolia (China), so groundwater levels were recorded in five monitoring wells from 2011 to 2016 and in 57 irrigation wells and two multilevel wells in 2016. Results showed that groundwater level in the groundwater irrigation area had two troughs each year, induced by extensive groundwater extraction, while groundwater levels in the river-diverted (Yellow River) water irrigation area had two peaks each year, resulting from surface-water irrigation. From 2011 to 2016, groundwater levels in the groundwater irrigation area presented a decreasing trend due to the overextraction. Groundwater samples were taken for geochemical analysis each year in July from 2011 to 2016. Increasing trends were observed in groundwater total dissolved solids (TDS) and As. Owing to the reverse groundwater flow direction, the Shahai Lake acts as a new groundwater recharge source. Lake water had flushed the near-surface sediments, which contain abundant soluble components, and increased groundwater salinity. In addition, groundwater extraction induced strong downward hydraulic gradients, which led to leakage recharge from shallow high-TDS groundwater to the deep semiconfined aquifer. The most plausible explanation for similar variations among As, Fe(II) and total organic carbon (TOC) concentrations is the expected dissimilatory reduction of Fe(III) oxyhydroxides.