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This paper describes the existence of high salinity in an inland aquifer system of a limited extent located in the granitic terrain of south India. Salinity levels observed in 55 water samples collected pre- and post-monsoon are discussed. Limited repeat sampling during the two seasons shows no significant change in hydrochemistry, probably due to the prevailing drought conditions during the study period (2017–18). As per the salinity classification based on total dissolved solids (TDS), only one sample indicates freshwater while ~ 40% of the samples are slightly saline, and the remaining have moderate salinity. All the high TDS samples are located over a limited area, and most show the water type as Ca–Mg–Na–Cl–SO4. Hydrochemical data indicate a gradual increase in salinity from west to east. Mainly two distinct processes (1) reverse ion exchange and (2) evaporation are likely to have influenced the groundwater chemistry. Variation in water chemistry between granite and gneiss formations indicates the influence of geology on hydrochemistry. Insignificant changes in hydrochemistry for the limited repeat sampling during pre and post-monsoon periods show a meagre recharge due to failed monsoon. However, depleted stable isotope values with reference to high TDS suggest faster recharge conditions in the granitic region than in the gneissic region. Accumulation of high salinity in the groundwater is restricted to the granitic area. We postulate that the presence of Hornblende Biotite Gneiss along the southern parts of the granitic region may be acting as a boundary for accumulating saline groundwater in a limited area in this region. However, it needs confirmation through further detailed geological and geophysical studies. [ABSTRACT FROM AUTHOR]

The Karst aquifers are usually characterized by high spatial heterogeneity in the humid tropics and subtropics, evidenced by specific landforms features (e.g., heavily fractured outcrops, sinkholes, etc.) and complex subterranean conduit networks. The marked high heterogeneity leads to the temporal–spatial variability of hydrological and hydro-chemical processes, making its environments extremely vulnerable to natural and anthropogenic hazards. The complicated temporal–spatial variability of hydrochemistry in karst systems depends on several underlying factors which influence the hydro-chemical processes. Investigating the factors of the karst water hydrochemistry variability is necessary to understand the hydro-chemical processes and mitigate natural and anthropogenic hazards for ensuring the sustainability of karst water resources. In this paper, an attempt is made to couple geostatistical and geochemical analysis to extract the underlying controlling factors and effective information about the geochemical evolution behave of karst water in Houzhai karst area, southwestern China. Factor analysis was performed to obtain significant statistical relationship of the hydrochemistry variation in the Houzhai karst basin. The ordinary kriging method was applied to the factor scores to investigate the contributions of factors on different regions. The results of the factor analysis indicated four principal factors which explained > 81.678% of the total sample variance: (1) the dilution effect by rainfall; (2) the dissolution effect dominated by calcite; (3) the human agricultural activities effect; (4) the migration of dissolved components under the control of alkaline environments in karst water. It revealed that the dilution effect was more significant (36.579%) than the dissolution effect (22.036%) and human agricultural activities effect (14.596%). These factors made more significant difference of contributions on the karst area in the dry periods than in the rainy periods. The dilution process by rainfall and the dissolution process of carbonate rock had a great influence on the upstream area whereas the human agricultural activities played important roles in the middle-stream area, especially in the dry periods. This integrated approach which combine factor analysis with kriging method is effective in the identification and interpretation of factors related to the variability of hydrochemistry, as well as the contributions of these factors on space and time. [ABSTRACT FROM AUTHOR]

The biological value of natural and protected areas like nature reserves is often reflected in the diversity and combination of different vegetation associations. In settings where the vegetation is strongly groundwater dependent, the specific interrelation between groundwater flow characteristics (hydrodynamics) and groundwater composition (hydrochemistry) is usually the most important factor for controlling the ecological value and occurrence of site-specific vegetation. Consequently, small-scale variations in ecological gradients within the site rather than its overall size are the key features that control the biodiversity of groundwater-dependent ecosystems. This is demonstrated for a small nature reserve called 'Gulke Putten' in the northwest of Belgium which is only a few km large, but shows an interesting variety in groundwater types the occurrence and genesis of which are due to local and highly seasonal flow conditions. As a result, the site has a high ecological value which is rare in this part of the country. This paper shows how multi-year daily water level measurements were used to quantify seasonal and inter-yearly variation in water levels and flow situations and how these are related to the condition in groundwater chemistry. Different hydrochemical facies are found, ranging from evaporated rainwater and waters influenced in varying degree by calcite dissolution, pyrite oxidation, cation exchange and some marine influence originating from the marine sediments of Tertiary age in the phreatic aquifer. This paper relates the variations in flow conditions and groundwater seepage intensity to the groundwater chemistry and helps to understand the origin of the abiotic ecological gradients that are related to the specific eco-hydrological value of the site. [ABSTRACT FROM AUTHOR]

Essentuki mineral groundwater (EMGW) basin is characterized by unique and complex geological and hydrogeological settings due to monoclinal character of the geological structure, breaking by north-eastern faults, significant stratum of clays, overlaying major aquifers, volcanic laccolite peaks. EMGW area involves the unique wide variety of mineral waters with different TDS, pH, chemical, and gas composition. TDS changes from fresh (0.5–0.9 g/L) to high salinity (10–13 g/L) and strongly depends on the chemical composition of water. The region is characterized by a wide spread of high pCO2 sparkling Ca–Na–HCO3–Cl waters, which are the trademark of "Essentuki 4" and "Essentuki 17". Such waters have strong therapeutic properties. Geothermal conditions, major- and micro-elements, isotopic characteristics of water (δ18O and δ2H) and gas (δ13C in CO2 and CH4, 3He/4He) phases of carbon dioxide mineral waters of EMGW basin were analyzed in this paper. The CO2free gas is probably a mixture of gas from deep (volcanic) and biogenic sources, although methane has the marine microbial origin and evolves from the degradation of dispersed organic matter in the host rocks. 3He/4He values prove that the free associated gas in mineral groundwaters of the region is a mixture of several sources of gas (mantle, crustal, and biogenic). [ABSTRACT FROM AUTHOR]

Groundwater over-exploitation leading to quality deterioration is an accepted fact, but limited work in this direction has been carried out in the Indian state of Punjab, where groundwater development is 172 %, the highest of any state in India. This paper makes an assessment of the groundwater quality in three administrative blocks of Rupnagar district in Punjab, in two of which groundwater exploitation has already reached about 200 %. Sixty groundwater samples were collected from shallow tubewells and hand pumps in premonsoon season (May, 2013) and were analyzed for major chemical parameters. Analytical results do not show any perceptible deterioration in groundwater quality; all the parameters are well within the permissible limits of the Indian standards, except for electrical conductivity (EC), total dissolved solids (TDS), Ca and Mg, which exceed the desirable limits in few groundwater samples. Abundance of ions in the water samples is in the order: HCO > Cl > SO > NO and Mg > Ca >N a > K. Data plotted on the US Salinity Laboratory diagram show that most of the samples fall in the category of CS and CS, which makes the groundwater suitable for irrigation in all types of soil. Other chemical indices such as % sodium (%Na), sodium absorption ratio (SAR), and residual sodium carbonate (RSC) also show that almost all samples are fit for irrigation purposes. This work thus concludes that groundwater quality deterioration due to irrigation has not yet been well perceived in the state of Punjab, even if much of its groundwater resources have been over-exploited. However, the paper warns against indiscriminate drilling and over-exploitation of the groundwater resources for their long-term usage and sustainability. [ABSTRACT FROM AUTHOR]

In the Republic of Djibouti (Horn of Africa), fractured volcanic aquifers are the main water resources. The country undergoes an arid climate. Alluvial aquifers exist in the wadis (intermittent streams) valleys and, in relation with volcanic aquifers, form complex volcano-sedimentary systems. Due to increasing water demands, groundwater resources are overexploited and require a rigorous management. This paper is focused on the Dalha basalts aquifer, located in the Dikhil area (Southwest of Djibouti). This aquifer is of vital importance for this area. Hydrochemical data and isotopic tracers ( 18O and 2H) were used to identify factors and phenomena governing the groundwater’s mineralization. The Piper diagram shows complex water types. Results from multivariate statistical analyses highlight three water families according to their locations: (1) groundwater characterized by low ionic concentrations located at the wadis zones; (2) groundwater characterized by moderate salinity and (3) highly mineralized waters mainly flowing in the eastern and central part of the study area, in volcanic aquifers. Results from scatter plots, especially Na versus Cl and Br versus Cl, suggest that the origin of more saline waters is not from dissolution of halite. The δ 18O and δ 2H data indicate that the groundwater flowing in the alluvial aquifer is of meteoric origin and fast percolation of rainwater occurs in the volcanic aquifers. These findings provide a preliminary understanding of the overall functioning of this complex volcano-sedimentary system. Additional investigations (pumping tests, numerical modeling) are in progress to achieve a more comprehensive understanding of this system. [ABSTRACT FROM AUTHOR]

This paper reports a hydrogeological characterization of a groundwater-dependent lakes system, the Lakes Kosi Bay catchment located in the north-eastern coast of South Africa. Conventional hydrogeological techniques including water balance analysis, hydrogeochemical and environmental isotope methodologies were applied in the study. Three distinct aquifer systems are recognized in the area, namely the unconfined Holocene cover sands, the Kosi Bay and Port Durnford Formations, and the Umkhwelane and Uloa Formations. Groundwater recharge to the topmost aquifer, which is connected to the lakes, is estimated using the chloride mass balance method to be 12 % of the mean annual precipitation (MAP = 939 mm/a). Evaporation rate from the lakes and evapotranspiration from the catchment are 1310 and 1135 mm/a, respectively. The mean annual water balance components indicate a positive balance between inputs and outputs. Groundwater flows from the west through the lakes (flow-through lakes) to the Indian Ocean. Groundwater in the shallow Holocene aquifer and streams has similar hydrochemical and isotopic signature indicating strong interconnection. These groundwater and streams have a hydrochemistry dominated mainly by a Na–Cl–HCO3 water type, a very low salinity (ranging from 88 to 400 µS/cm) and a negative isotopic signature (negative δD and δ18O values). The lakes are characterized by Na–Cl hydrochemical water type, have salinity that ranges from 1014 to 25,300 µS/cm, and positive stable isotopic signature (positive δD and δ18O signature) indicating strong evaporation effects. The study further reveals a salinity and isotopic series among the lakes from south to north, towards the estuary. [ABSTRACT FROM AUTHOR]

The objective of this work is to compare the chemical composition and the spatial and temporal variabilities of groundwater in two basins, the Langueyú and Del Azul creeks basins, located in the Pampean plain, Buenos Aires province (Argentina). The Pampean plain is the most productive region in Argentina, agriculture and livestock being the main economic activities. Groundwater is the principal water resource in the region, with a strong and growing demand for human supply and for agriculture and industrial activities. Several sampling campaigns were carried out on shallow wells of the two studied basins along a period of 3 years (2010–2013) to identify seasonal variations. Electrical conductivity, pH, bicarbonate, chloride, sulphate, nitrate, calcium, magnesium, sodium and potassium were determined following standard methods. For hydrochemical interpretation, descriptive statistical analyses, matrix augmentation principal component analysis, MA-PCA, and multidimensional principal component analysis, N-PCA (Parafac and Tucker3 models), were applied to the hydrochemical datasets from both basins. Three main hydrochemical processes have been identified in both basins: saline enrichment in the groundwater flow direction caused by dissolution of carbonates; exchange of calcium and magnesium by sodium in the same direction, and located areas of nitrate pollution. The paper shows that N-PCA is a good tool to deepen in the understanding of the hydrochemical features of groundwater from two neighbour basins, simplifying the analysis of large amounts of data, as well as establishing relations between the compared basins. Therefore the work is considered an interesting contribution to the study of groundwater resources with a regional scope. This knowledge is essential in basins with high socio-economic interests it causes a direct impact on resources management. [ABSTRACT FROM AUTHOR]

This paper presents the trophic state index (TSI) and water physico-chemical characteristics of a shallow tropical reservoir located in southeast Brazil. It describes a study held over a hydrological and diurnal period, which enabled to map the variability of several physico-chemical variables due to regional climate and to compare the results with the TSI in winter and summer. The thermal behavior of the water column is typical of a polymictic reservoir. Low dissolved oxygen levels have been measured, reaching 0.07 mg L in the deepest part of the reservoir as a direct consequence of the increased nutrient levels. The average pH was slightly acid (6.71) especially at the reservoir bottom and did not show significant changes during the monitoring period. The electrical conductivity varied according to seasons, i.e., it was higher in the rainy period compared to dry season, averaging 138 and 84.06 µS/cm, respectively. According to the TSI, the reservoir has been classified as mesotrophic and eutrophic in the dry and rainy season, respectively. [ABSTRACT FROM AUTHOR]

Estimating vulnerability of a karst system to pollution is a major current issue. However, to assess vulnerability, an understanding of the karst system functioning is necessary. The aim of this paper was to characterize the degree of karst network development used by flows (i.e. karst system functioning) to have a better knowledge on the resource and its vulnerability to any possible contamination. This characterization can be done with an analysis of water chemistry emerging from a system. Carbon dioxide partial pressure (Pco) and saturation index with respect to calcite (SI) are two significant parameters that can be used to study water chemistry of karst systems through calcium-carbonate equilibriums. These enable the implementation of the SI-Pco method. In this article, a methodology is proposed based on the SI-Pco method coupled with frequency distribution analysis and principal components analysis (PCA). This study considers three karst systems with a developed saturated zone and one epikarst spring, located near the Fontaine de Vaucluse spring (Southeast France). Results show that different water types and flowing conditions in the karst system are identified. From this acquired information, karst network development can be estimated. Finally, results can aid in the vulnerability assessment of karst systems. [ABSTRACT FROM AUTHOR]

This paper describes a hydrochemical (major and trace elements) and stable isotopes (H, O, S) study of rainwater and groundwater in a Guarani Aquifer System (GAS) transect at São Paulo State, Brazil. The Brazilian Code of Mineral Waters (BCMW) was adopted for the groundwater temperature classification, allowing adequate insights in the hydrochemical data. H and O data in circa 580 rainwater samples at São Paulo State have been selected, showing a wide dispersion (δO from −21.5 to +4.9 ‰ V-SMOW; δH from −162 to +43.2 ‰ V-SMOW). The H and O data in groundwater did not vary significantly, fitting the regional meteoric water line and indicating that the groundwater origin is directly related to the meteoric water precipitation. The δO values in groundwater collected along the GAS transect did not indicate a tendency towards more negative values according to the groundwater flow direction at São Paulo State as suggested elsewhere. The δO and δO data indicated that the dissolved sulfate is obtained from previous sulfate dissolution. The δS and δO data of dissolved SO suggested that the dissolution of evaporites and bacterial SO reduction processes may be occurring at the GAS. The temperature, redox potentials, dissolved oxygen and organic matter content in the sediments provided an ideal environment for the δS and δO changes along the GAS transect, accompanying the groundwater flow direction. [ABSTRACT FROM AUTHOR]

Groundwater is one of the major sources of water in Isfahan. Efficient management of these resources requires a good understanding of its status. This paper focuses on the hydrochemistry and also it wants to assess the nitrate concentration in irrigation groundwater of Isfahan suburb. All the groundwater samples are grouped into three categories, including Na-Cl + Ca-Cl (63 %), Na-SO + Ca-SO (23 %) and Ca-HCO (14 %). According to the EC and SAR, the most dominant classes are C3S1, C4S2 and C4S3. 55 % of samples indicate very high salinity and medium to very high alkalinity that is not suitable for irrigation. 84 % of the groundwater samples show nitrate contents higher than HAV (13 mg l), while more than 25 % exceeded the maximum contamination level (44.27 mg l) according to EPA regulations. The horizontal and vertical distribution patterns of nitrate in groundwater samples show a surficial origin for nitrate contamination. The high nitrate content can be attributed to the agricultural activities along with domestic sewage and industrial wastewaters in populated area. Based on results, using high nitrate groundwater for irrigation can minimize the requirement for inorganic fertilizers and reduce the cost of cultivation and nitrate contamination. [ABSTRACT FROM AUTHOR]

This paper examines the issues related to salinization and water quality in the complex drainage system of the historical land reclamation of Lamone basin (Ravenna coastal plain, northern Italy), with the aim of guiding ongoing agricultural-related decisions. Major and trace element concentration and O-H-B-Sr isotope-ratios were measured on surface water from a network of canals and ditches. Sampling was carried out during the winter period and in summer, to assess the effects of agricultural water management on the aquatic system. Results show widespread salinization of waters over the entire crop, due to both the direct saltwater inland flushing through the canals in proximity of the mouths, and sea salt leaching from soils. During winter, salinization is partly mitigated by rainfalls, while in summer dilution processes are due to freshwater input from outside the watershed, planned to assist the agricultural water demand. In the winter season, the concentration of some elements such as Fe, Mn, Al, and Cu in waters exceeds the maximum permissible limits imposed by the Italian regulations, while during summer the concentration of these elements is significantly reduced. A seasonal cycling is established, where the bottom sediments of canals and ditches act as sinks of harmful elements, mostly through adsorption by Fe-Mn-Al oxy-hydroxide solid phases. The irrigation practice, although improving the water quality, increases water turbidity by re-mobilization of sediments which act as transport agents of contaminants, with detrimental effects that may become significant over the years. [ABSTRACT FROM AUTHOR]

This paper discusses the hydrochemistry variation and its quality status in Langat River, based on the chemistry of major ions, metal concentrations and suitability for drinking purposes. Water samples were collected from 30 different stations to assess their hydrochemical characteristics. The physico-chemical parameters selected were temperature, electrical conductivity, total dissolved solids (TDS), salinity, dissolved oxygen , pH, redox potential, HCO, Cl, SO, NO, Ca, Na, K, Mg, Al, Ba, Be, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Se and Zn to investigate the variation of the constituents in the river water. Most of the parameters comply with the Drinking Water Quality Standard of the World Health Organization and the Malaysian National Standard for Drinking Water Quality by the Malaysia Ministry of Health except for EC, TDS, Cl, HCO, SO, Na, Mg, Al, Fe and Se. The results show that the Langat River is unsuitable for drinking purposes directly without treatment. [ABSTRACT FROM AUTHOR]

The paper discusses the ionic sources and chemical quality of the waters (surface and groundwater) around the Tehri reservoir in Uttarakhand, Garhwal, Himalaya, for drinking and irrigation purposes. The main Bhagirathi river, tributary streams and springs and groundwater are the main sources of water for the reservoir and inhabitant living around it. Fifty-two water samples were collected from springs, handpumps (borewell) and streams and were analysed for major ions. The pH is varying from 6.8 to 8.6 and EC from 28 to 820 μS/cm. The chemical composition of water is dominated by Ca, Mg and HCO. The high ratio of Ca + Mg /Na + K and low ratio of Na + K/TZ indicate dominance of carbonate dissolution as the main solute acquisition process in this part of Lesser Himalaya. The trilinear and X-Y plots suggest less contribution from silicate weathering and anthropogenic activities. The excess of Na over Cl indicating much of the alkalis in the waters of Tehri area have source other than precipitation possibly from silicate weathering. Recharged by meteoric water, the quality of water in the study area is controlled essentially by chemical processes occurring between water and lithology and locally altered by human activities. Among the trace metals the concentration of Fe at few locations has marginally exceeded the WHO and BIS standards of drinking water. The analytical result computed from various water quality indices indicate fairly good quality of water for both drinking and irrigation purposes. The factor analysis performed on the major ion data indicate two factors are the most important affecting the water quality of the area. [ABSTRACT FROM AUTHOR]

Karstic limestone formations in the West Mountain area are important water resources for Taiyuan City in Shanxi Province, northern China, which is also known for its large-scale coal mining production. In this study area, groundwater is not only exploited for water supply purposes but also drained because of coal mining. The process of coal mining changes both the quantity of the karst springs and the quality of karst groundwater system because of overexploitation and overdrainage. In this paper, the influence of coal mining on the groundwater is analyzed from a qualitative and quantitative perspective. The hydrochemical analysis results reflect the relationship of the recharge, runoff, and drainage; the features of the medium; and water-rock interactions. Based on a qualitative understanding of the geological deposition and characteristics of the groundwater flow system, three-dimensional groundwater flow models are established and applied to several scenarios to explore the quantitative influence and allow better protection of the groundwater environment and better utilization of water resources. [ABSTRACT FROM AUTHOR]

The impacts of environmental flow controls on the water table and chemistry of groundwater in the Ejina Delta, an arid inland river basin in northwest China, were investigated with field observations in 2001 and 2009. The results indicate that the shallow groundwater level rose by 0-2 m in the upper reaches of the east tributary of the Heihe River and in the areas of Saihantaolai-Dalaikubu during the period of environmental flow controls. The chemical constituents of the groundwater show a distinct spatial heterogeneity with the total dissolved solids (TDS) in the groundwater increasing from the periphery towards the depocenter of the Ejina Basin. In addition, the rate of groundwater cycling in the south of the Ejina Delta increased, and the mineralization of groundwater declined, while the overall mineralization and salinity increased in the northern regions, especially in the depocenter of the Ejina Basin. Since shallow groundwater is important to the ecology of arid regions, and because understanding the changes in the shallow groundwater environment (groundwater level and hydrochemistry) in response to environmental flow controls is essential for the sustainable improvement of the ecological environment, the results of this paper can be used as a reference for watershed water resources planning and management to help maintain the health and proper function of rivers in arid regions. [ABSTRACT FROM AUTHOR]

To identify the mechanism of geothermal water in Xiaoyangkou Geothermal Field, the earliest medium-temperature, high-yield geothermal resource found in Subei Basin, based on the water quality indicators of four geothermal water and one groundwater samples, hydrogeochemical and isotopic methods were used to analysis the hydrochemical characteristics, recharge sources and circulation depth of geothermal water, and to determine the reservoir temperature. Results show that the temperature of the thermal reservoir of the Neogene Yancheng Formation is about 39.5–41.64 °C. The geothermal waters are HCO3 type with TDS of 616–638 mg/L. The temperature of the Paleogene Funing Formation and Devonian–Silurian sandstone reservoir is about 95.45–110.78 °C. The geothermal waters are SO4 type with TDS of 1446–1812 mg/L. The concentrations of trace elements F, Sr and Li increased rapidly with the increase of temperature. The isotopic compositions of δ18O and δD indicates that the geothermal water is mainly recharged by atmospheric precipitation from the elevation of 145.5–524.5 m. The atmospheric precipitation infiltration is heated by the heat flow in the deep part and transported upward along the water-conducting structure through deep circulation (3.37 km) to the karst fissure at the top of the underlying strata of Yancheng Formation, forming a convective geothermal system. The upper Yancheng formation is an associated-conduction geothermal system. The research results provide reference and basis for the rational development and utilization of geothermal resources in the region. [ABSTRACT FROM AUTHOR]

A hydrogeochemical study was carried out on the shallow Catania Plain alluvial aquifer, in eastern Sicily to reconstruct its hydrogeological structure, the meteoric recharge and to assess the influence of human activities on groundwater. To characterize the geochemistry of the shallow aquifer, two sampling campaigns were carried out, August–October 2004 and April–May 2005 in 47 sites distributed throughout the plain. The samples were collected and analyzed for physical–chemical parameters and major ions, as well as stable isotopes (δ18O and δ2H). Alluvial deposits with heterogeneous grain sizes constitute the aquifer. Varying conditions of vertical and horizontal permeability lead to the presence of a multilayered aquifer with different conditions of confinement and partial interconnection among layers. The sampled waters were separated into four groups of different compositions due to the water–rock interaction with the different lithologies present in and around the study area. Maps of electrical conductivity and sulfate show a systematic control of land use, in correspondence with the biggest farms. High sulfate concentration is due to both the natural interaction between local meteoric waters and Etna's plume and the mixing with groundwater coming from the area where evaporitic rocks of the Gessoso Solfifera formation are present. In addition, anthropogenic contamination cannot be ruled out. A rain gauge network, consisting of 3 sites located at different altitudes, was installed to collect rain waters to determine isotopic data (δ2H and δ18O) and to measure the monthly rainfall amount. Based on the isotopic composition of sampled waters, it has been established that beyond the direct meteoric recharge, the recharging areas are in the North (Mt. Etna) and the South (Hyblean Plateau). [ABSTRACT FROM AUTHOR]

Recently, the groundwater became very important source for the Egyptian water balance. Therefore, assessing its quality and quantity is necessary before initiating any developmental plans using this resource. In this research, a new operated power plant, which is located in the coastal area of West New Damietta City, north-east of Egypt was designed to work using the coastal groundwater aquifer. Therefore, an integrated approaches of both geophysical methods and hydrochemical analysis were applied to identify the subsurface lithology, the water-bearing layers and determine the potential use of such coastal groundwater. Therefore, a total of seventeen vertical electrical soundings (VES) and five time-domain electromagnetic soundings (TEM) were performed. Moreover, groundwater samples were collected from seven existing wells to be analyzed for water quality assessment. The geophysical results identified five geoelectric layers. The first geoelectric layer has a resistivity of 1–7.9 Ω m and a thickness range of 7–9 m. The second layer has a resistivity of 0.9–4.4 Ω m and a thickness range of 7–8 m. The third layer is 10–21 m thick with a resistivity value of 0.5–2 Ω m. The fourth layer, which is thicker (29 to 42 m), has a resistivity of 0.7–3 Ω m, while the last layer has a resistivity of 1.7–9 Ω m. According to the hydrochemical analysis, the aquifer is dominated by Na–Cl water type. The brackish nature of the water is revealed by the TDS range of 7035 mg/l to 7735 mg/l. The results collected demonstrate the groundwater's quantity and quality availability for the power plant's sustainable use. [ABSTRACT FROM AUTHOR]

In the North China Plain, water shortage seriously restricts economic development, and agricultural irrigation depends heavily on groundwater extraction. Irrigation water and precipitation may directly recharge groundwater in the irrigated agricultural region. Therefore, calculating the recharge of precipitation and irrigation to groundwater is essential for the sustainable utilization of water resources. Furthermore, determining the transformation relationship of precipitation-soil water-groundwater is helpful to understand the hydrological cycle process better. The average groundwater recharge calculated by the chloride mass balance method is between 66 and 144 mm/year, accounting for only 7–17% of the total precipitation and irrigation water. The hydrogen (2H) and oxygen (18O) isotopes reveal that precipitation only affects soil water in topsoil, and soil water in deep soil is recharged upward by groundwater. The hydrochemical composition of soil water shows high concentrations of salt in unsaturated zones. Infiltration water dissolves salt through the unsaturated zone and carries them into the shallow groundwater, causing the deterioration of shallow groundwater quality. These results contribute to the effective management of groundwater resources and the control of agricultural pollution in groundwater. [ABSTRACT FROM AUTHOR]

Karst aquifers typically have desirable physicochemical properties and can provide an important source of groundwater for drinking. Kiyan karst springs, located in the geological region of the Zagros (western Iran), consist of two springs (Keder and Zolal) situated 3 m apart. The water of Zolal spring is always clear, with no turbidity during rainfall or earthquake phenomena, but Keder spring, which also provides drinking water to a city of 10,000 inhabitants (Kiyan city), has very high turbidity in these conditions. This situation disrupts the drinking water supply for about 1 month per year in the study area. The interpretation of discharge time series diagrams, precipitation, and turbidity in different rainfall and earthquake conditions, composite diagrams, and stable isotope concentrations show this study area to be a well-developed karst environment with a highly eroded tectonic zone and large karst conduits along with turbulent water flow. In general, the difference in the behavior of the two springs is related to different paths of water movement through the drainage area. The two springs share the same source of recharge from rainfall and the same initial underground drainage path from the largest sinkhole in the region; although the path of water movement is divided into two branches, with Zolal spring water entering a narrower fault channel. In the Zolal spring pathway, a siphon-shaped reservoir is formed where muddy rainwater settles, so that the water from this spring is clear but has higher concentrations of some ions analyzed here than Keder spring water. [ABSTRACT FROM AUTHOR]

In the Precambrian granitic terrain, the occurrence of a multi-aquifer system is common. This study has examined the inter-communications between the shallow and deep aquifers using the hydrochemical and isotopic methods. The obtained results indicate distinct hydrochemical characters of the groundwater from shallow (~ 100 m) and deep (~ 400 m) wells, signifying their independent and unconnected nature initially. Hydrochemistry of deep groundwater is approximately constant (either Ca–Na–Cl or Ca–Na–Cl–SO4 type of water) from January 2015 to June 2016. Repeated measurements of the 14C activity in these deep groundwater samples during this period show 35.41 ± 0.48 to 85.01 ± 0.8 pMC (residence time of ~ 3 to 8 ky BP). However, as a result of excess rainfall during 2016, hydrochemical facies of the deep groundwater changed initially to Na–Ca–SO4–Cl. Subsequently, they stabilised at Ca–Na–HCO3–Cl type with a significant reduction in Cl− and increased HCO3− and NO3− concentrations, while the 14C activity changed to 100 pMC (modern age). These changes are attributed to the ingression of fresh water into the deep aquifer after paleo-groundwater in the deep aquifer is depleted due to the over-exploitation of the limited potential aquifer during the drought. The over-exploitation of deep aquifer possibly improved the migration potential of fresh water to the deep aquifer and led to enhancing the groundwater recharge during the excess rainfall years. It brings a new perspective to the hydrogeological dynamics between shallow and deep aquifers. Further, it also suggests that, under climate-driven drought conditions, deep aquifers could act as an emergent groundwater resource to meet the water demands. A conceptual model has been proposed to explain the observed phenomenon of deep and shallow aquifer communication. [ABSTRACT FROM AUTHOR]

Hydrochemical analysis, geological study and evaluation of hydrogeochemical processes play a crucial role to understand the variability of fluoride ion concentration in groundwater. The present study is focused on a watershed boundary comprising of parts of two river basins namely Ruparail and Banganga within Bharatpur district of Rajasthan in India. Administratively, the study area is covered in five blocks of Bharatpur district viz. Deeg, Kaman, Nagar, Pahari and Kumher. The study area and sampling locations were identified based on the spectral signatures of satellite data, literature study and field-based experience. Seventy-five groundwater samples were collected for pre and post-monsoon seasons, separately. The hydrochemical results have shown that Banganga basin has experienced greater fluoride enrichment in groundwater as compared to Ruparail basin. Both the basins have experienced more groundwater samples in the class of high-risk water (more than 1.5 mg/l F−) during the post-monsoon season due to mineral dissolution with the surface run-off water in the aquifer material. The shallow aquifers (< 40 m bgl) have experienced high fluoride distribution in groundwater as compared to deeper aquifers (> 40 m bgl). The spatiotemporal interpolation maps for fluoride ion concentration generated by following inverse distance weighted (IDW) method have shown the varied fluoride concentration with geologic, geomorphic and seismo-tectonic features. Chadha's plot for hydrochemical facies has revealed that the groundwater of the study area is mainly of Na–Cl and Ca–Mg–Cl type. The evaluation of hydrochemical facies has suggested that Na–Cl water type is having elevated fluoride ion concentration as compared to Ca–Mg–Cl and Ca–Mg–HCO3 water types. The interpretation of hydrogeochemical processes based on scatter plots of hydrochemical parameters has revealed that processes such as silicate weathering, direct-ion exchange, mineral dissolution and rock–water interaction are responsible for fluoride augmentation in groundwater. The enrichment is also governed by evaporation, semiarid environment, salinity hazard and overdraft of groundwater. The water types having inhibited fluoride ion concentration are found dominated with carbonate weathering and recharge water (Ca–Mg–HCO3 type) and reverse-ion exchange process (Ca–Mg–Cl type). Moreover, the geochemical modeling is indicative of under-saturation of fluorite with over-saturation of calcite and dolomite, augmenting fluoride ion concentration in groundwater. The comprehensive understanding of hydrogeochemical processes controlling fluoride enrichment is found useful for planning strategies adopted for providing safe drinking water in a sustainable way. [ABSTRACT FROM AUTHOR]

The city of Caldas Novas, State of Goiás, Brazil, holds the largest thermal water complex in the planet not associated to with volcanism or other kinds of magmatism. Its structural control allows the fractures to be wide and deep enough so the waters can reach 1000 m depth. These waters are extracted mainly by deep wells, from the exploitation of the Paranoá and Araxá Aquifer Systems, emerging at temperatures higher than 59 °C. With a growing demand for water resources, groundwater exploration became an attractive alternative for public supply, due to its abundance, quality and low abstraction cost. In Caldas Novas, due to the population growth over the last decades and the increasing number of tourists, a disordered groundwater consumption drawdown the water levels. In order to survive, these reservoirs depend on rainwater infiltration rates to replenish the thermal springs; however, the lack of environmental management and the high risk of contamination, due to the unconsolidated materials thinness, may threaten the thermal aquifer. This study was based on the hydrochemical characterization of Caldas Novas Thermal Complex waters, including radioactive parameters, whose descriptions in the literature are still scarce. Besides, concerning the prospective increase on touristic activities, physicochemical water analyses are periodically required, being this paper a contribution for such purpose. [ABSTRACT FROM AUTHOR]

In the coastal region of Bangladesh, groundwater is mainly used for domestic and agricultural purposes, but salinization of many groundwater resources limits its suitability for human consumption and practical application. This paper reports the results of a study that has mapped the salinity distribution in different aquifer layers up to a depth of 300 m in a region bordering the Bay of Bengal based on the main hydrochemistry and has investigated the origin of the salinity using Cl/Br ratios of the samples. The subsurface consists of a sequence of deltaic sediments with an alternation of more sandy and clayey sections in which several aquifer layers can be recognized. The main hydrochemistry shows different main water types in the different aquifers, indicating varying stages of freshening or salinization processes. The most freshwater, soft NaHCO3-type water with Cl concentrations mostly below 100 mg/l, is found in the deepest aquifer at 200-300 m below ground level (b.g.l.), in which the fresh/saltwater interface is pushed far to the south. Salinity is a main problem in the shallow aquifer systems, where Cl concentrations rise to nearly 8000 mg/l and the groundwater is mostly brackish NaCl water. Investigation of the Cl/Br ratios has shown that the source of the salinity in the deep aquifer is mixing with old connate seawater and that the saline waters in the more shallow aquifers do not originate from old connate water or direct seawater intrusion, but are derived from the dissolution of evaporite salts. These must have been formed in a tidal flat under influence of a strong seasonal precipitation pattern. Long dry seasons with high evaporation rates have evaporated seawater from inundated gullies and depressions, leading to salt precipitation, while subsequent heavy monsoon rains have dissolved the formed salts, and the solution has infiltrated in the subsoil, recharging groundwater. [ABSTRACT FROM AUTHOR]

Complex structural systems, lithological differences, and extreme heterogeneity of aquifers combine to create a complex karst aquifer structure in alpine and gorge areas; however, because of the topography, direct investigation of aquifer structure is difficult. In this study, field survey, hydrochemical, and isotopic data are analyzed to reveal the development of karst groundwater and to describe the karst water cycle in Genie Mountain, Qinghai–Xizang Plateau. The results show that groundwater circulation is mainly controlled by active fracture. Atmospheric precipitation and melting ice and snow are the groundwater recharge sources, and recharge areas are mostly located in high mountains above 4500 m a.s.l. The direction of groundwater flow is mostly controlled by the Jinshajiang active Fault, with drainage areas at the intersection of multiple faults. There are two regional karst water runoff conduits. One is along the Edexi-Hongjunshan Fault, where groundwater runs from south to north; the other is along Gangtonglong Fault, where groundwater runs from north to south, and is discharged at Gangtonglong gully. The groundwater cycle can be divided into three levels: epikarst water circulation; mid to deep karst water circulation; and deep geothermal water circulation. The karst springs located in the outlet of the Huolong gully contain markedly higher levels of Na+ and SO42− than other karst springs because of the leaching effect of groundwater on mirabilite. The presence of evaporites in Huolong gully indicates that the plateau planation formed by the structural uplift will change the local climatic conditions, and then affect the groundwater circulation process and the water–rock reaction in the process. [ABSTRACT FROM AUTHOR]