Hydrochemical Facies Research Articles

The influence of lithology and climatic conditions on the groundwater quality in the semi-arid-regions: case study of the Eastern Middle Cheliff alluvial aquifer (northwestern Algeria)

Over the last few years, the Eastern Middle Cheliff plain has witnessed remarkable economic growth, particularly in the agricultural sector. However, the overexploitation of the alluvial aquifer, coupled with agricultural practices involving the use of fertilizers and pesticides, significantly contributed to the degradation of groundwater quality. The primary objective of this study is to comprehend the mechanisms governing the water chemistry of the Eastern Middle Cheliff alluvial aquifer. A total of 42 samples were collected and analyzed during the dry periods of the 2012 and 2017. The data processing and representation involved the utilization of analytical tools including Principal Component Analysis (PCA), Piper diagram, Stabler classification, binary diagrams, base exchange indices, saturation indices, and geostatistical methods. The interpretation of these data revealed the following findings: i) the groundwater in both the dry periods of 2012 and 2017 is characterized by the presence of two dominant hydro-chemical facies, namely calcium chloride and sodium chloride, as indicated by the Piper and Stabler diagrams; ii) the hydrochemical quality of the groundwater varies across different regions of the aquifer, fair to poor in the eastern and central regions, with the presence of certain contaminants resulting from the application of nitrates in agricultural activities. The quality is classified as very poor in the western region, primarily due to high salinity influenced by the lithology of the aquifer, the rise of deep salty water through the Cheliff fault due to the earthquake of the year 1980 and possibility by two climatic factors, namely evaporation and rainfall. Overall, this study provides new insights into the water chemistry dynamics of the Eastern Middle Cheliff alluvial aquifer, highlighting the varying hydrochemical facies and the impact of agricultural activities and climatic factors on groundwater quality in different areas of the aquifer.

Hydrogeochemical study of groundwater in arid and semi-arid regions of the Infracenomanian aquifers (Cretaceous Errachidia basin, Southeastern Morocco). Using hydrochemical modeling and multivariate statistical analysis

Groundwater in the Cretaceous Errachidia basin, located in the southern part of Morocco, is crucial in supporting the region's main economic activities, such as farming. This arid region faces multiple challenges, including an average annual rainfall of less than 80 mm/year, intense agricultural activities, high evaporation, and extremely high evapotranspiration rates up to 1580 mm/year. Therefore, the hydrogeochemical study focuses on the Infracenomanian aquifers in the Cretaceous Errachidia basin. The goal is to evaluate the sustainable use of saline lands and brackish water, particularly assessing water resources and sustainable socioeconomic development in southeastern Morocco. In June 2021, 20 samples were collected and analyzed for pH, electrical conductivity (EC), total dissolved solids (TDS) and major ions. The hydrogeochemical parameters were analyzed using multivariate statistical methods. Statistical techniques such as Piper's trilinear diagram analysis of hydrochemistry types, Gibbs diagram analysis, The HFE diagram and ion correlation analysis were used to examine the origins of the main ions in the groundwater and to determine the source of the salinization processes in the groundwater.The findings revealed a strong positive correlation between TDS and the spatial distribution of major ions (Na+, Ca2+, Mg2+, Cl−) and EC, revealing high mineralization in the study area. The main cations in groundwater are Na+ and Ca2+, while the main anions are Cl−. The elevated concentrations of Cl− and Na+ are due to the evapotranspiration of irrigation water. Furthermore, the hydrochemical facies types are predominantly sodium chloride (Na–Cl), followed by calcium chloride (Ca–Cl) and a mix of calcium and magnesium chloride facies (Ca–Mg–Cl). These analyses indicate that the hydrochemistry of groundwater in the study area is primarily influenced by water-rock interactions, such as the dissolution of sedimentary rocks, soil leaching through gravity irrigation, and evaporation in the region. Moreover, the analysis using the Gibbs diagram indicates that evaporation is the primary hydrogeochemical process that shapes the chemical composition of the groundwater in the area under study.

Integrated approach to hydrogeochemical appraisal of groundwater quality concerning arsenic contamination and its suitability analysis for drinking purposes using water quality index

Arsenic (As), contamination in drinking groundwater resources is commonly environmental problem in many developing countries including Pakistan, with significant human health risk reports. In order to examine the groundwater quality concerning As contamination, its geochemical behavior along with physicochemical parameters, 42 samples were collected from community tube wells from District Bahawalpur, Punjab, Pakistan. The results showed the concentration of elevated As, its source of mobilization, and associated public health risk. The As concentration detected in groundwater samples varied from 0.12 to 104 µg/L with an average value of 34.7 µg/L. Among 42 groundwater samples, 27 samples were beyond the permitted limit of 10 µg/L recommended by World Health Organization (WHO), for drinking purposes. Statistical analysis result show that the groundwater cations values are in decreasing order such as: Na+ > Mg2+ > Ca2+ > K+, while anions were HCO3– > SO42– > Cl– > NO3–. Hydrochemical facies result depict that the groundwater samples of the study area, 14 samples belong to CaHCO3 type, 5 samples belong to NaCl type, 20 samples belong to Mixed CaMgCl type, and 3 samples belong to CaCl2 type. It can be accredited due to weathering and recharge mechanism, evaporation processes, and reverse ion exchange. Gibbs diagram shows that rock water interaction controls the hydrochemistry of groundwater resources of the study area. Saturation Index (SI) result indicated the saturation of calcite, dolomite, gypsum, geothite, and hematite mineral due their positive SI values. The principal component analysis (PCA) results possess a total variability of 80.69% signifying the anthropogenic and geogenic source of contamination. The results of the exposure-health-risk-assessment method for measuring As reveal significant potential non-carcinogenic risk (HQ), exceeding the threshold level of (> 1) for children in the study area. Water quality assessment results shows that 24 samples were not suitable for drinking purposes.

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

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

Hydrogeochemical Evaluation of Aquifer Storage and Recovery in Edwards Aquifer, New Braunfels, Texas.

This study examines the potential for aquifer storage and recovery (ASR) in the brackish portion of the Edwards aquifer in New Braunfels, Texas. Successful ASR relies on understanding hydraulic properties, aquifer heterogeneity, water geochemistry, and geochemical processes during operations. The research aims to investigate the chemistries of native groundwater and injectant during ASR operation, estimate the hydraulic properties of the aquifer layers, and assess the recovery rate for the recovered groundwater meeting the total dissolved solids (TDS) threshold. The study found that native groundwater is of Na-Cl facies due to halite dissolution and a possible basinal brine migration associated with the zone of greatest fault displacement. High sulfate ions in background native groundwater result from sulfate-bearing minerals' dissolution in the Kainer and Person Formations. The injectant water is of Ca-Mg-HCO3 facies due to the carbonate-rich composition of the aquifer host matrix and interaction with the Guadalupe River riverbed. During ASR operations, mixing controlled the shift in hydrochemical facies from Na-Cl to Ca-Mg-HCO3.The study also suggests a possible connection between Kainer and Person Formations and preferential pathways in the targeted storage zone aquifer. The estimated conductivity values also indicate dominant horizontal flow via possible fracture pathways in both the Person and Kainer Formation storage zones. Recovery of groundwater meeting the TDS of 1000 mg/L requires a recovery rate of 0.03 m3/s for 60 days after 40-day storage. This research emphasizes that understanding the hydrogeological conditions and geochemical processes is critical to ASR feasibility in brackish carbonate multi-aquifer fractured systems.

Probabilistic modelling is superior to deterministic approaches in the human health risk assessment: an example from a tribal stretch in central India

This case drew national attention in 2018. About 100 people died and more than 300 hospitalized in a span of few years in a village of 1200 people in a tribal stretch in central India. Medical teams visiting the area reported severe renal failure and blamed the local eating and drinking habits as causative factors. This human health assessment based on geochemical investigations finds nitrate (NO3−) and fluoride (F−) pollution as well in village’s groundwater. Both deterministic and probabilistic techniques are employed to decipher the contamination pathways and extent of contamination. Source apportionments of NO3− and F− and their relationship with other ions in groundwater are carried out through chemometric modelling. Latent factors controlling the hydrogeochemistry of groundwater too are explored. While hazard quotients (HQ) of the chemical parameters (HQ_{{{text{NO}}_{3}^{ - } }} and HQ_{{{text{F}}^{ - } }}) identify ingestion as the prominent pathway, the calculated risk certainty levels (RCL) of the hazard index (HI) values above unity are compared between the deterministic and probabilistic approaches. Deterministic model overestimates the HI values and magnify the contamination problems. Probabilistic model gives realistic results that stand at infants (HI_{{{text{NO}}_{3}^{ - } }} = 34.03%, HI_{{{text{F}}^{ - } }} = 24.17%) > children (HI_{{{text{NO}}_{3}^{ - } }} = 23.01%, HI_{{{text{F}}^{ - } }} = 10.56%) > teens (HI_{{{text{NO}}_{3}^{ - } }} = 13.17%, HI_{{{text{F}}^{ - } }} = 2.00%) > adults (HI_{{{text{NO}}_{3}^{ - } }} = 11.62%, HI_{{{text{F}}^{ - } }} = 1.25%). Geochemically, about 90% of the samples are controlled by rock-water interaction with Ca2+–Mg2+–HCO3− (~ 56%) as the dominant hydrochemical facies. Chemometric modelling confirms Ca2+, Mg2+, HCO3−, F−, and SO42− to originate from geogenic sources, Cl− and NO3− from anthropogenic inputs and Na+ and K+ from mixed factors. The area needs treated groundwater for human consumption.

Spatial characteristics of hydrochemistry and stable isotopes in river and groundwater, and runoff components in the Shule River Basin, Northeastern of Tibet Plateau

Water resources play a crucial role in constraining the high-quality development of the arid, necessitating an in-depth investigation and understanding of hydrological processes, hydrochemical characteristics, and their influencing factors amidst climate change. This study meticulously examined and analyzed the hydrochemistry and stable isotope composition (δ18O and δD) of river and groundwater within the Shule River Basin (SRB). Results showed that both river (mean: 8.01) and groundwater (mean: 7.92) had alkaline pH values, while average total dissolved solids were measured at 709.25 mg/L in river and 861.88 mg/L in groundwater, indicating predominance of fresh water sources. HCO3−, SO42−, Na+ and Ca2+ were the most abundant ions, influenced by evaporation-crystallization processes and rock weathering. The dominated hydrochemical facies in both river and groundwater were Ca–HCO3 type in the upper (UR) and the middle reaches (MR), while Ca–Mg–Cl type in the lower reaches (LR). The local meteoric water line (LMWL) was defined as δD = 8.01δ18O + 18.48 (R2 = 0.98, n = 163; P < 0 0.001). The more negative δ18O and δD values in river and groundwater were plotted nearby and lower right of the LMWL, implying that the important recharge source of those waters is from precipitation. The relationship between river δ18O and elevation showed an increase of 0.14‰/100 m in the UR, but a negative correlation with a rate of −0.47‰/100 m in the MR and LR. Precipitation, groundwater, baseflow and meltwater accounted for 62.5%, 19.8%, 11.9% and 5.8% of the UR river, respectively, during the observed period, according to the end-member mixing analysis. These runoff components displayed distinct seasonal variations, primarily driven by precipitation during the early and groundwater/baseflow during the rapid and end-stage ablation periods. The observed alterations in hydrological elements present both opportunities and challenges for water resource management across the SRB, and adaptive measures have been proposed based on our study. These findings provide valuable insights into efficient utilization of water resources from water chemistry and environmental isotopes.

Analysis of the Recharge Area of the Perrot Spring (Aosta Valley) Using a Hydrochemical and Isotopic Approach

The Perrot Spring (1300 m a.s.l.), located to the right of the Chalamy valley in the Monte Avic Natural Park (Valle d’Aosta, Italy), is an important source of drinking water for the municipality of Champdepraz. This spring is located on a large slope characterised by the presence of a Quaternary cover of various origins (glacial, glaciolacustrine, and landslide) above the bedrock (essentially serpentinite referred to the Zermatt–Saas Zone, Penninic Domain). Water emerges at the contact between the landslide bodies and impermeable or semi-permeable glaciolacustrine deposits. The aim of this study is to define the processes and recharge zones of this spring. The analysis of the data revealed the presence of two contributions to the Perrot Spring input: a spring thaw contribution defined by a small increase in flow and an autumn contribution from rainwater infiltration. The low average temperature and low variation of the annual temperature (4.8–6.5 °C) suggest a sufficiently deep flow circuit. Chemical analyses showed a groundwater chemistry consistent with the regional geology: the hydrochemical facies is calcium–magnesium bicarbonate and isotopic analyses (δ2H and δ18O) of rainfall and spring water suggested a recharge altitude of about 2100 m a.s.l. In conclusion, this study makes it possible to recognize the water inputs to the spring discharge and to delineate its recharge area, which can be proposed to implement strategies to protect the resource.

Comprehensive evaluation of hydro-chemical processes, suitability, health risks, and sources of groundwater contamination using compositional data analysis, Nizampur basin, Pakistan

This study aimed to evaluate the level of contamination, health risks, hydro-chemical processes, and sources of contaminants in the groundwater of the Nizampur basin, northwestern Pakistan. Forty-eight (n = 48) groundwater samples from predefined locations were collected and analyzed using the standard procedure for a total of 13 parameters. Statistical techniques in the compositional data analysis perspective were used for the identification of sources. The results showed that TDS, Turbidity, SO4, and NO3 concentrations surpassed the limits in 44, 29, 25, and 48% of samples, respectively. The nitrate pollution index indicated that 48% of the samples were contaminated with nitrates, while the composite index PIG showed that only 22% of the samples indicated low pollution. A close association between the land use/land cover of the study area and NO3 contamination was observed. In general, the groundwater of the region could be categorized as fresh-very hard water (87.5%), the major hydro-chemical facies were, Ca–Mg–HCO3, followed by mixed Ca–Mg–Cl and Ca–Cl facies. The Van Wirdum diagram showed that groundwater was mainly influenced by rock weathering and profound human impact. Similarly, it was assessed using chloro-alkaline indices that reverse ion exchange is a governing hydro-chemical process. NO3 concentrations in the area have the potential to cause non-cancer ailments in 75% and 47% of the samples in children and adults respectively. Based on the assessments made using the compositional data analysis it was inferred that NO3, SO4, Cl, and Turbidity originated from human sources, while the rest of the parameters have natural/geogenic sources.

Spatial distribution of hydrochemical facies and its impact on groundwater utilization

Spatial distribution of hydrochemical facies and its impact on groundwater utilization

Hydro-geochemistry and Related Processes Controlling the Composition of Thermal Waters in the Lake Natron Basin, Northern Tanzania

Lake Natron Basin (LNB) forms part of the eastern branch of the East African Rift System (EARS) in Tanzania. The basin is endowed with thermal springs flowing towards the lake from the western, northwestern, southwestern and eastern parts. The western, northwestern and south-western thermal springs emanate from fractures in the basaltic rocks while in the east, they originate from the western flank of the Gelai volcano. There are limited studies on these springs, thus their geochemical differences and distributions of physicochemical parameters are not well understood. A hydrogeochemical study was conducted to interpret available geochemical data from the LNB springs, including cold and thermal water to allow their geochemical characterization. Results have shown that LNB water is dominated by sodium (Na+), chloride (Cl-) and bicarbonate (HCO3-) ions. Three hydro-chemical facies have been identified forming Na-Cl, Na-HCO3 and Ca-HCO3 water types. This study has also revealed that thermal water in the north-western part of the basin is highly mineralised and gradually becomes diluted toward south-west and south due to groundwater incursion. Water-CO2-rock interaction affects the overall chemistry of thermal water leading to HCO3- water, particularly in the east of the basin. While few springs from the western side of the basin indicated maturity of the thermal waters, other springs indicated mixed Cl-HCO3/peripheral water; while the cold waters are HCO3 type. It is recommended to take precautions when planning geothermal projects to avoid corrosion and scaling of production facilities. Similarly, mixing or dilution of thermal water with shallow groundwater can affect the temperature and the composition of Cl-.

Hydrochemical Facies Description to Assess the Groundwater Quality in Southern Part of Haditha District, Iraq

The current study explains the hydrochemical processes controlling the variance in the hydrochemical facies for eighteen samples obtained from the study area. The groundwater samples were analyzed for the major ions "cations and anions" data in mg/l, total dissolved solids (TDS) in mg/l, electrical conductivity (EC) in μS/cm, pH unit less, and temperature in °C. Piper trilinear (three-line) diagram indicates the overall of samples belong to class 1 (Ca2+, Mg2+, Cl-, SO42-), category I (SO42- - Cl- and Ca2+ - Mg2+) and permanent total hardness (calcium chloride type). The contribution of cations in the study area was different percentages (dominant cation sodium (Na+)), while the sulfate (SO42-) is the dominant ion of the groundwater in the study area. The analytical values showed that overall the samples were brackish water and high enrichment salts within the impermissible limits of the World Health Organization standards. Irrigation parameters and water quality index were calculated for samples to assess water for agricultural and drinking uses for the inhabitants of the study area. The basic exchange is the exchange of sodium (Na+) and potassium (K+) ions in water with magnesium (Mg2+) and calcium (Ca2+) ions in materials which are exposed to weathering.

Deployment of entropy information theory in the Indian Sundarban region using hydrogeochemical parameters and GIS for assessment of irrigation suitability.

The evaluation of irrigation suitability plays a crucial role for the socio-economic development of the society, especially in the region of Sundarban. For sustainable agricultural practices, groundwater quality must be suitable for irrigation; otherwise, it can degrade soil and diminish crop yield. The entropy information theory, several irrigational indices, multivariate statistics, GIS, and geostatistics are used in this work to evaluate the geographical distribution and quality of groundwater in the Indian Sundarban region. In total, 33 groundwater samples were collected in 2018 (April and May), and they were evaluated for major cations, anions, as well as other parameters like electrical conductivity (EC), soluble sodium percentage (SSP), potential salinity (PS), total dissolved solids (TDS), Kelly ratio (KR), sodium absorption ratio (SAR), permeability index (PI), residual sodium carbonate (RSC), magnesium hazard (MH), and residual sodium bicarbonate (RSBC). The overall trend of the principal cations and anions is in the sequence of Na+ ≥ Mg2+ ≥ Ca2+ ≥ K2+ and HCO3- ≥ Cl- ≥ NO3- ≥ SO42- ≥ F-, respectively, whereas the spatial variation of %Na, SAR, RSBC, and MH demonstrate very poor irrigation water quality, and spatial variation of KR, RSC, SSP, PI, and PS signifies that the irrigation water quality is excellent to good. In order to identify the specific association and potential source of the dissolved chemical in the groundwater, statistical techniques like correlation and principal component analysis were also employed. The hydrochemical facies indicates that mixed type makes up the bulk (51.51%) of the water samples. Following the Wilcox plot, more than 75% of the water samples are good to doubtful; however, by the US salinity hazard map, roughly 60.60% of the samples had high salinity (C3-S1 zone). The EWQII reports that no samples fall into the very good (no restriction) category, whereas 30.30%, 30.30%, and 39.40% of the sample wells record good (low restriction), average (moderate restriction), and poor (severe restriction) irrigation water quality, respectively. Based on this study, the bulk of the groundwater samples taken from the study area are unsuitable for cultivation. The findings of this study will also help decision-makers develop adequate future plans for irrigation and groundwater resource management.

Identifying the hydrochemical features, driving factors, and associated human health risks of high-fluoride groundwater in a typical Yellow River floodplain, North China.

Fluoride enrichment (> 1.5mg/L) in groundwater has become a global threat, particularly given the hazards to human health. This study collected 58 unconfined groundwater samples from Fengpei Plain in June 2022 for hydrochemical and stable isotope analyses combined with multiple methods to explore sources, influencing factors, and potential health hazards of groundwater F-. The results showed that groundwater F- concentration ranged from 0.08 to 8.14mg/L, with an average of 1.91mg/L; over 41.4% of them exceeded the acceptable level of 1.5mg/L prescribed by the World Health Organization (WHO). The dominant hydrochemical facies changed from Ca·Mg-HCO3 and Ca·Mg-SO4·Cl type in low-F- groundwater to Na-HCO3 and Na-SO4·Cl water types in high-F- groundwater. The Self-Organizing Map (SOM) and ionic correlation analysis indicated that F- is positively correlated to pH, EC, Na+, K+, SO42-, and TDS, but negatively to Ca2+ and δ18O. Groundwater F- accumulation was primarily driven by F--bearing minerals dissolution such as fluorite. Simultaneously, the carbonates precipitation, positive cation exchange processes, and salt effect were conducive to groundwater F- enrichment. However, competitive adsorption between OH-/HCO3- and F-, evaporation, and anthropogenic activities only had a weak effect on the F- enrichment in groundwater. The hazard quotient (HQ) assessment results show that 67.2% of groundwater samples pose a non-carcinogenic risk (HQ > 1) for infants, followed by 53.4% for children, 32.8% for females, and 25.9% for males. The Monte Carlo simulation results agreed with those of the deterministic model that minors are more susceptible than adults. These findings are vital to providing insights into the geochemical behavior, driving factors, and drinking water safety of high-F- groundwater worldwide.

Analysis of self-organizing maps and explainable artificial intelligence to identify hydrochemical factors that drive drinking water quality in Haor region

Water contamination undermines human survival and economic growth. Water resource protection and management require knowledge of water hydrochemistry and drinking water quality characteristics, mechanisms, and factors. Self-organizing maps (SOM) have been developed using quantization and topographic error approaches to cluster hydrochemistry datasets. The Piper diagram, saturation index (SI), and cation exchange method were used to determine the driving mechanism of hydrochemistry in both surface and groundwater, while the Gibbs diagram was used for surface water. In addition, redundancy analysis (RDA) and a generalized linear model (GLM) were used to determine the key drinking water quality parameters in the study area. Additionally, the study aimed to utilize Explainable Artificial Intelligence (XAI) techniques to gain insights into the relative importance and impact of different parameters on the entropy water quality index (EWQI). The SOM results showed that thirty neurons generated the hydrochemical properties of water and were organized into four clusters. The Piper diagram showed that the primary hydrochemical facies were HCO3−-Ca2+ (cluster 4), Cl---Na+ (all clusters), and mixed (clusters 1 and 4). Results from SI and cation exchange show that demineralization and ion exchange are the driving mechanisms of water hydrochemistry. About 45 % of the studied samples are classified as “medium quality”,” that could be suitable as drinking water with further refinement. Cl− may pose increased non-carcinogenic risk to adults, with children at double risk. Cluster 4 water is low-risk, supporting EWQI findings. The RDA and GLM observations agree in that Ca2+, Mg2+, Na+, Cl− and HCO3− all have a positive and significant effect on EWQI, with the exception of K+. TDS, EC, Na+, and Ca2+ have been identified as influencing factors based on bagging-based XAI analysis at global and local levels. The analysis also addressed the importance of SO4, HCO3, Cl, Mg2+, K+, and pH at specific locations.

Hydrogeochemistry, ionic speciation, controlling processes and agricultural suitability of groundwaters in sections of the semi-arid basement complex of north–central Nigeria

In order to ascertain the governing mechanisms, sources, and speciation of ionic species, identify hydrochemical facies, and assess their appropriateness for agricultural use, groundwaters from several portions of the semi-arid basement complex of north–central Nigeria were analyzed based on chemistry. Basement aquifers made of gneiss-migmatites, metasediments, and granitoids store groundwater. Standard analytical techniques were used to analyze the fluids for main cations, anions, and physical characteristics. The results showed that the waters were slightly acidic (with a mean pH of 5.38, below the permissible range of 6.5–8.5), and that the predominant cations and anions were Na+ >Ca2+ >K+ >Mg2+ and Cl− > NO3- > HCO3- > SO42−, respectively. Analysis of the ions' stoichiometric ratios reveals that alkali elements predominate, making up about 55.3% of the ions and being connected to silicate weathering. Based on ionic ratio calculations, it was determined that ion exchange was a key factor controlling water chemistry. Ionic species cross plots show that silicate weathering (sodic and calcic plagioclase) predominates. Hydrochemical facies, Gibbs plots, and principal component (correlation, cluster and factor) studies all show that ionic elements are geogenic, essentially coming from the weathering of silicates with ion exchanges. Based on predicted saturation indices, hydrochemical modeling by the computer program VISUAL-MINTEQ reveals that the majority of main ions occur in free mobile states with associated mineral species, all at undersaturated levels. Based on measurements of the sodium adsorption ratio (SAR), sodium percentage (% Na), and chloro-alkaline indices (CAI), the waters have been evaluated for their suitability for agricultural use.

Hydro-Geochemical Characteristics of the Shallow Alluvial Aquifer and Its Potential Artificial Recharge to Sustain the Low Flow of the Garonne River

The complex and interconnected water challenges linked to global climate change and natural and anthropogenic water resources pressure have become major challenges in the 21st century. The Garonne River and its accompanying alluvial aquifers are considered the most important source for agricultural activities in the Garonne Valley, Nouvelle-Aquitaine Region, southwest France. The water is used for irrigation in summer and to reduce frost damage in spring. The alluvial shallow aquifer is recharged by rainfall, lateral inflow from the hillside, and seepage from the riverbed during the flood periods. The aquifer maintains the flow of the river during dry periods. Moreover, the potential recharge of this aquifer is particularly sensitive to annual climatic fluctuations and consequently affects surrounding ecosystems and related socio-economic activities. The increasing impacts of climate change have increased the concern about the availability of these resources. Various adaptation strategies have been considered to mitigate and adapt to the new situation in southwest France. The artificial recharge of the alluvial aquifer is one such regional adaptation strategy to adapt to climate change. The study has two main objectives: to assess the natural and anthropogenic influence on the groundwater chemistry, and to model water infiltration, and understand the aquifer response and, consequently, the effects on river baseflow. The TAG (Technopole Agen-Garonne) project aims to increase the economic wealth of the region while respecting the region’s agricultural traditions. Runoff water from the TAG zone is collected in retention basins and is a potential source to recharge the shallow alluvial aquifer. Sampling campaigns were carried out during the summer of 2019 to collect groundwater samples from several observation wells. Groundwater levels were measured in 132 wells/boreholes to determine the groundwater level fluctuations and create piezometric maps. Piper, spatial distribution, and ionic ratio plots were used to determine the dominant hydrochemical processes and to delineate the hydrochemical facies in the study area. The groundwater chemistry is controlled by silicate weathering and anthropogenic influence. Groundwater quality appears to be affected by the river water in the wells located in the low plain area. The measurements showed that the groundwater levels in the wells located near the river increase more than 2 m after a flood event. The artificial recharge has increased the groundwater level by more than 1 m close to the infiltration basin after a rainstorm. Similarly, a three-dimensional (3D) groundwater model shows a similar magnitude aquifer response to the induced infiltration. The modeling-obtained result shows that the infiltrated water would take about 4 months to reach the Garonne River, which is an appropriate time to maintain the river’s low-flow and thermal buffering capacity, and thus the functioning of its ecosystems during dry periods.

Use of hydrogeochemical tools to evaluate seawater intrusion: a case study of Upper Pliocene Aquifer in the Ca Mau Peninsula, Vietnam

Groundwater resources have been withdrawn significantly to meet the demands of agricultural economic development in the Ca Mau Peninsula, Mekong River Delta. As a result, aquifers face the risk of groundwater levels decline and high salinization potential. This study uses the groundwater quality index (GQI) and hydrochemical facies evolution diagram (HFE-D) to assess the hydrochemical characteristics and salinization potential of the Upper Pliocene aquifer (n2 2), which is one of the two most exploited aquifers in the Mekong River Delta. A total of 6 monitoring wells were used to observe groundwater level and water quality from 2017 to 2020. The GQI results ranged from 33.38 to 75.61, indicating that groundwater in Hau Giang and Soc Trang areas is salinized. The spatial distribution results of HFE-D stated that the boundaries of intrusion and freshening have varied in space and time. Specifically, the Upper Pliocene aquifer has been in the process of seawater intrusion. The freshwater area in the Ca Mau has been gradually shrinking in the East Sea area faster than the West Sea area. The displacement speed of the intrusion and freshening boundary varied considerably from 0.04 to 0.67 km/year from 2017 to 2020.

Assessment of Hydrochemical Facies on Groundwater Quality in Daenaa Village and its Surroundings, West Limboto District

The study is required to evaluate the groundwater condition, such as finding the relationship with the lithology, determining the facies of groundwater, and providing an overview of the present groundwater conditions, genetics, and groundwater quality. This study aims to explain the relationship between lithology and groundwater chemistry, groundwater quality, and the determination of the chemical facies of groundwater to determine the genetic type of groundwater. This study uses field survey methods and random sampling techniques, measurements of groundwater physical properties, trilinear piper diagrams, and laboratory analysis in the form of rock geochemical analysis (XRF) at the PSDMBP Laboratory and chemical analysis of groundwater at the PT Global Quality Analytical Laboratory. The results show that the lithology in the study area consists of clastic limestone, sandstone, breccia, and dacite. Lithology in the study area primarily plays an essential role in chemical ion enrichment in groundwater. Determination of groundwater quality is based on Permenkes, Permen ESDM, and ISDW, which obtained eleven well points in the good quality category, five well points in the poor quality category, and four other well points categorized as poor quality. Based on the analysis results in the trilinear piper diagram, there is one type of groundwater chemical facies (not varied), namely the Ca-Cl type facies. The presence of the Ca-Cl facies type is interpreted as a seawater intrusion phase.

The machine learning and geostatistical approach for assessment of arsenic contamination levels using physicochemical properties of water.

Arsenic contamination in groundwater due to natural or anthropogenic sources is responsible for carcinogenic and non-carcinogenic risks to humans and the ecosystem. The physicochemical properties of groundwater in the study area were determined in the laboratory using the samples collected across the Varanasi region of Uttar Pradesh, India. This paper analyses the physicochemical properties of water using machine learning, descriptive statistics, geostatistical and spatial analysis. Pearson correlation was used for feature selection and highly correlated features were selected for model creation. Hydrochemical facies of the study area were analyzed and the hyperparameters of machine learning models, i.e., multilayer perceptron, random forest (RF), naïve Bayes, and decision tree were optimized before training and testing the groundwater samples as high (1) or low (0) arsenic contamination levels based on the WHO 10 μg/L guideline value. The overall performance of the models was compared based on accuracy, sensitivity, and specificity value. Among all models, the RF algorithm outclasses other classifiers, as it has a high accuracy of 92.30%, a sensitivity of 100%, and a specificity of 75%. The accuracy result was compared to prior research, and the machine learning model may be used to continually monitor the amount of arsenic pollution in groundwater.