Dominant Water Type Research Articles

Assessment of seasonal groundwater quality and potential saltwater intrusion: a study case in Urmia coastal aquifer (NW Iran) using the groundwater quality index (GQI) and hydrochemical facies evolution diagram (HFE-D)

Coastal aquifers are at threat of salinization in most parts of the world. This work investigated the seasonal hydrochemical evolution of coastal groundwater resources in Urmia plain, NW Iran. Two recently proposed methods have been used to comparison, recognize and understand the temporal and spatial evolution of saltwater intrusion in a coastal alluvial aquifer. The study takes into account that saltwater intrusion is a dynamic process, and that seasonal variations in the balance of the aquifer cause changes in groundwater chemistry. Pattern diagrams, which constitute the outcome of several hydrochemical processes, have traditionally been used to characterize vulnerability to sea/saltwater intrusion. However, the formats of such diagrams do not facilitate the geospatial analysis of groundwater quality, thus limiting the ability of spatio-temporal mapping and monitoring. This deficiency calls for methodologies which can translate information from some diagrams such Piper diagram into a format that can be mapped spatially. Distribution of groundwater chemistry types in Urmia plain based on modified Piper diagram using GQIPiper(mix) and GQIPiper(dom) indices that Mixed Ca–Mg–Cl and Ca-HCO3 are the dominant water types in the wet and dry seasons, respectively. In this study, a groundwater quality index specific to seawater intrusion (GQISWI) was used to check its efficiency for the groundwater samples affected by Urmia hypersaline Lake, Iran. Analysis of the main processes, by means of the Hydrochemical Facies Evolution Diagram (HFE-Diagram), provides essential knowledge about the main hydrochemical processes. Subsequently, analysis of the spatial distribution of hydrochemical facies using heatmaps helps to identify the general state of the aquifer with respect to saltwater intrusion during different sampling periods. The HFE-D results appear to be very successful for differentiating variations through time in the salinization processes caused by saltwater intrusion into the aquifer, distinguishing the phase of saltwater intrusion from the phase of recovery, and their respective evolutions. Both GQI and HFE-D methods show that hydrochemical variations can be read in terms of the pattern of saltwater intrusion and groundwater quality status. But generally, in this case (i.e. saltwater and not seawater intrusion) the HFE-D method was presented better efficiency than GQI method (including GQIPiper and GQISWI).

Assessment of solute and suspended sediments acquisition processes in the Bara Shigri glacier meltwater (Western Himalaya, India)

Various physico-chemical parameters of meltwater samples from Bara Shigri glacier collected during 2012–2013 were analysed to understand the dissolved ion chemistry and solute acquisition processes regulating major ion chemistry of the study area. Ionic dominance of anions followed the trend as HCO3− > SO42− > Cl− > NO3−, whereas ionic dominancy of cations varied as: Ca2+> Mg2+> K+> Na+ for both the years. High share of (Ca + Mg) in the total cations and also dominancy of (Ca + Mg) over (Na + K) for both the years demonstrate that solute acquisition processes in the meltwater of Bara Shigri glacier are mainly governed by the weathering of carbonates. The Piper plot identified Ca-HCO3 as the dominant water type followed by CaSO4 type of water in the study area. The average value of partial pressure of carbon dioxide (Pco2) for meltwater of the Bara Shigri glacier was 10−2.6 atm in 2012 and 10−2.3 atm in 2013 and were higher than the Pco2 value of atmosphere (10−3.5 atm). It indicates that the meltwater is in disequilibrium with respect to the atmosphere. Contents of suspended sediment in the meltwater were 1432 mg/l in July and 596 mg/l in September 2012, whereas in 2013, suspended sediment contents were 1093 mg/l in August and 425 mg/l in September, following discharge pattern of the Bara Shigri glacier. We found that Bara Shigri and Gangotri glaciers demonstrate the higher rate of regional melting.

Use of major ion and stable isotope geochemistry to delineate natural and anthropogenic sources of nitrate and sulfate in the Kettle River Basin, British Columbia, Canada

The Kettle River Basin in South central British Columbia (Canada) is under increasing anthropogenic pressures affecting both water quantity and quality of surface waters and aquifers. We investigated water quality and sources and processes influencing NO3– and SO42– in the Kettle River Basin using a combination of chemical and isotopic techniques. The dominant water type in the Kettle River Basin is Ca–HCO3 with surface waters having total dissolved solids (TDS) concentrations of<115mg/L and groundwaters having TDS values of up to 572mg/L. Based on δ15NNO3 and δ18ONO3 values and concentration data, NO3– in surface waters originates primarily from natural soil nitrification processes, with additional influences from anthropogenic activities, such as waste water effluents at sampling locations downstream from population centres. The source of NO3– in groundwater was predominantly nitrification of soil organic matter, although nitrate in a few groundwater samples originated from anthropogenic sources, including manure or septic systems. The dominant source of SO42– in surface water and groundwater samples was the natural oxidation of sulfide minerals. With increasing distance downstream, surface water δ18OSO4 values increase beyond the range of oxidation of sulfide minerals and into the range of soil and atmospheric-derived SO42– that is in part derived from anthropogenic emissions. Hence, we conclude that recent anthropogenic impacts have affected water quality only marginally at only few sites in the Kettle River Basin. The presented data will serve as an excellent baseline against which future impacts can be assessed.

Identifying the origin and geochemical evolution of groundwater using hydrochemistry and stable isotopes in the Subei Lake basin, Ordos energy base, Northwestern China

Abstract. A series of changes in groundwater systems caused by groundwater exploitation in energy base have been of great concern to hydrogeologists. The research aims to identify the origin and geochemical evolution of groundwater in the Subei Lake basin under the influence of human activities. Water samples were collected, and major ions and stable isotopes (δ18O, δD) were analyzed. In terms of hydrogeological conditions and the analytical results of hydrochemical data, groundwater can be classified into three types: the Quaternary groundwater, the shallow Cretaceous groundwater and the deep Cretaceous groundwater. Piper diagram and correlation analysis were used to reveal the hydrochemical characteristics of water resources. The dominant water type of the lake water was Cl-Na type, which was in accordance with hydrochemical characteristics of inland salt lakes; the predominant hydrochemical types for groundwater were HCO3–Ca, HCO3–Na and mixed HCO3–Ca–Na–Mg types. The groundwater chemistry is mainly controlled by dissolution/precipitation of anhydrite, gypsum, halite and calcite. The dedolomitization and cation exchange are also important factors. Rock weathering is confirmed to play a leading role in the mechanisms responsible for the chemical composition of groundwater. The stable isotopic values of oxygen and hydrogen in groundwater are close to the local meteoric water line, indicating that groundwater is of modern local meteoric origin. Unlike significant differences in isotopic values between shallow groundwater and deep groundwater in the Habor Lake basin, shallow Cretaceous groundwater and deep Cretaceous groundwater have similar isotopic characteristics in the Subei Lake basin. Due to the evaporation effect and dry climatic conditions, heavy isotopes are more enriched in lake water than in groundwater. The low slope of the regression line of δ18O and δD in lake water could be ascribed to a combination of mixing and evaporation under conditions of low humidity. Comparison of the regression line for δ18O and δD showed that lake water in the Subei Lake basin contains more heavily isotopic composition than that in the Habor Lake basin, indicating that lake water in the discharge area has undergone stronger evaporation than lake water in the recharge area. Hydrochemical and isotopic information of utmost importance has been provided to decision makers by the present study so that a sustainable groundwater management strategy can be designed for the Ordos energy base.

Spatiotemporal Variations in Groundwater Chemistry of a Small Tropical Island Using Graphical and Geochemical Models

In this work, the spatial and temporal variations in the groundwater chemistry of Kapas Island were assessed using geochemical and graphical models. The Durov diagram classifies the groundwater of the island into three water types; Ca- HCO3-, Na- HCO3-, and Na-Cl types with Ca- HCO3− as the dominant water type. The Schoeller diagram reveals that the order of abundance in ions was Ca2+ > Na+> K+> Mg2+, for cations and HCO3− > Cl− > SO42− for anions. These findings would help in creating a sustainable management plan through strategizing visitations and pumping periods to ensure that the island's aquifer and other smaller islands with similar characteristics are well protected.

Evaluating the geochemistry of Bam salt dome in Hormozgan Province, Iran

Evaluation of the geochemistry and hydrochemical quality of Bam salt dome located in southern Iran, was conducted in this study. Two composite samples from salt units were collected and analysed by XRD and XRF to determine their mineral and elemental compositions. Water samples were also collected from the only spring in the area and analysed for major anions, cations and some toxic elements. The results indicated halite as the major mineral present, while quartz, anhydrite and dolomite were present at minor levels. The presence of anhydrite and dolomite together with quartz had negative effects on edible salt quality. The dominant water type in the area was sodium-chloride. Negligible sulphate and calcium contents may be attributed to anhydrites detected in the geological texture of the study area. According to a Schoeller diagram, the water is not suitable for drinking. Concentrations of toxic metals in the salt sample were significantly higher than those in water samples. Such a result can be viewed as an opportunity to produce edible salts from the evaporation of spring water.

Water type quantification in the Skagerrak, the Kattegat and off the Jutland west coast

An extensive data series of salinity, nutrients and coloured dissolved organic material (CDOM) was collected in the Skagerrak, the northern part of the Kattegat and off the Jutland west coast in April each year during the period 1996–2000, by the Institute of Marine Research in Norway. In this month, after the spring bloom, German Bight Water differs from its surrounding waters by a higher nitrate content and higher nitrate/phosphate and nitrate/silicate ratios. The spreading of this water type into the Skagerrak is of special interest with regard to toxic algal blooms. The quantification of the spatial distributions of the different water types required the development of a new algorithm for the area containing the Norwegian Coastal Current, while an earlier Danish algorithm was applied for the rest of the area. From the upper 50 m a total of 2227 observations of salinity and CDOM content have been used to calculate the mean concentration of water from the German Bight, the North Sea (Atlantic water), the Baltic Sea and Norwegian rivers. The Atlantic Water was the dominant water type, with a mean concentration of 79%, German Bight Water constituted 11%, Baltic Water 8%, and Norwegian River Water 2%. At the surface the mean percentages of these water types were found to be 68%, 15%, 15%, and 3%, respectively. Within the northern part of the Skagerrak, closer to the Norwegian coast, the surface waters were estimated to consist of 74% Atlantic Water, 20% Baltic Water, and 7% Norwegian River Water. The analysis indicates that the content of German Bight Water in this part is less than 5%.

Sources of salinity and urban pollution in the Quaternary sand aquifers of Dar es Salaam, Tanzania

Groundwater is globally important for human consumption, and changes in quality can have serious consequences. The study area is within a coastal aquifer where groundwater quality is influenced by various potential sources of salinity that determine the composition of water extracted from wells. Groundwater chemistry data from the aquifer have been acquired to determine the geochemical conditions and processes that occur in this area and assess their implications for aquifer susceptibility. Analysis of groundwater samples shows that the dominant watertype is mostly NaCl with pH<7 in both aquifers (i.e. upper and lower) except for the shallow wells where CaHCO3 prevails with pH⩾7, and boreholes located near the Indian Ocean, where coral reef limestone deposits are located and the watertype evolves towards CaHCO3. In the lower aquifer, Cl− is higher than in the upper aquifer. The origin of salinity in the area is strongly influenced by groundwater ascending from deep marine Miocene Spatangid Shales through faults, seawater incursion on the border of the Indian Ocean, and throughout, there is some salinity within the Quaternary aquifer, especially in intercalated deltaic clays in the fluviatile deposits, showing some marine influences. The seawater intrusion is linked to the strongly increasing groundwater exploitation since 1997. Another process that plays a major role to the concentration of major ions in the groundwater is calcite dissolution. Next to geogenic salinity and seawater intrusion, anthropogenic pollution as well is affecting groundwater quality in the aquifer. An important result of this study is the observation of high nitrate concentrations, that call for improved sanitation in the area, where domestic sewage with on-site sanitation (mainly pit latrines) also threatens the groundwater resource.

Geochemical signatures of groundwater in the coastal aquifers of Thiruvallur district, south India

An attempt has been made to identify the chemical processes that control the hydrochemistry of groundwater in the coastal aquifers of Thiruvallur coastal village of Thiruvallur district, Tamil Nadu, south India. The parameters such as pH, EC, TDS and major ion concentrations of Na, K, Ca, Mg, Cl, HCO3, SO4 and NO3 of the groundwater were analyzed. Abundances of these ions are in the following order Na > Ca > Mg > K and HCO3 > Cl > SO4 > NO3. The dominant water types are in the order of NaCl> mixed CaMgCl > CaHCO3 > CaNaHCO3. Water types (mixed CaHCO3, mixed CaMgCl and NaCl) suggest that the mixing of high salinity water caused from surface contamination sources such as irrigation return flow, domestic wastewater and septic tank effluents with existing water followed by ion exchange reaction processes, silicate weathering and evaporation are responsible for the groundwater chemistry of the study area. The above statement is further supported by Gibbs plot where most of the samples fall within the evaporation zone.

Hydrochemical assessment of surface water and groundwater quality along Uyyakondan channel, south India

Groundwater and surface water quality is an important factor that determines its usage for drinking and irrigational use. This study was carried out along a major irrigation water source—Uyyakondan channel in Tiruchirappalli, south India. Fourteen surface water samples along the channel and fifteen groundwater samples close to the surface water sampling locations were collected to determine its suitability for drinking and irrigational purposes. Electrical conductivity, pH and concentrations of calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, sulphate, fluoride and nitrate were determined in the water samples. The chemical composition of the water samples were compared with the drinking water standards of World Health Organisation and Bureau of Indian Standards. Groundwater from this area was suitable for drinking based on magnesium, sulphate, bicarbonate, fluoride and nitrate, while the concentration of calcium, sodium, potassium and chloride exceeded the maximum permissible limits at few locations. Surface water was within the permissible limits for magnesium, potassium, bicarbonate, sulphate, fluoride and nitrate, while calcium, sodium and chloride exceeded the highest desirable limits. Sodium chloride was the dominant groundwater and surface water type. Irrigation water quality was assessed based on magnesium hazard, residual sodium carbonate, sodium percentage, sodium adsorption ratio, permeability index and salinity hazard. Water was suitable for irrigation based on magnesium hazard and residual sodium carbonate. Most water samples were doubtful for irrigation use based on sodium percentage and good for irrigation depending on sodium adsorption ratio. Though 60 % of groundwater and 29 % of surface water samples were suitable for drinking based on water quality index, majority of the water samples were not suitable for irrigation. The water quality in this area needs to be monitored regularly and it is crucial to treat the water before consumption.

Evaluation of the groundwater quality with WQI (Water Quality Index) and multivariate analysis: a case study of the Tefenni plain (Burdur/Turkey)

Groundwater is a vital source of water for domestic and agricultural activities in the Tefenni plain. Therefore, groundwater quality, seasonal variations and its suitability for drinking, irrigation and industrial usage were evaluated. In this study, 56 water samples were collected from springs, wells, and lake in dry and wet seasons. Ca–Mg–HCO3, Mg–Ca–HCO3, Na–CO3–Cl, and Na–HCO3–Cl water types are the dominant water types in the investigation area. Parameters, which are controlled to chemical variations of groundwater, were analyzed with R-mode factor and correlation analysis. According to R-mode factor analysis, total dissolved solids, Na, Cl, HCO3, and NH3 are the most important parameters. In addition, Water Quality Index (WQI) was applied to suitability for drinking purpose and to investigation of groundwater quality. Quality of groundwaters are suitable for drinkable both dry and wet season in study area. In terms of the irrigation and industrial usage, generally groundwater is suitable in dry season but is not suitable in wet season. Groundwater chemistry is affected with water–rock interaction and densely agricultural activities.

Geochemical Assessment of Environmental Impact on Groundwater Quality in Coastal Arid Area, South Eastern Tunisia

Groundwater contamination has been recognized as one of the most serious problems in semi-arid and arid area (e.g. Zarzis aquifer, south-eastern Tunisia). The groundwater chemistry evolves rapidly and the salinity goes up considerably. A geochemical survey was carried out in which 23 groundwater samples were collected. EC, pH, TDS and major ions were measured and analyzed. Geochemical modeling, Piper Diagram, Q-mode hierarchical cluster and PCA were used to assess groundwater mineralization processes. Spatial variability of the different groundwater parameters was examined using semivariogram analysis. Results revealed that the Na-Cl-Ca-SO4-K is the dominant water type, suggesting rock-water interaction and dissolution of NaCl, CaSO4, 2H2O and KCl from sebkhas to be the main processes controlling groundwater mineralization in study area. Hierarchical Cluster Analysis (HCA) showed that groundwater is grouped in two clusters: the first, located in the southern part of the study area, is influenced by salt depressions in which a high potassium concentration was found. The second cluster characterized by rock-water interaction is located in the northern par of study area. Spatial development of groundwater flow and TDS were analyzed using variographic analysis and kriged maps were plotted. The method has succeeded in effectively extracting useful information, and improving the analysis of salinity and piezometric level, thereby playing an important role in qualitative and quantitative predictions. No reversal of the hydraulic gradient is detected in the study area, which eliminates any assumption on seawater intrusion in the region.

A Comparative Study of Ion Chemistry of Groundwater Samples of Typical Highland and Midland Sub-watersheds of the Manimala River Basin, Kerala, South India

Results of the detailed study of the chemistry of ions present in the groundwater samples of Peruvanthanam and Valiyathodu sub-watersheds of the Manimala river basin are analysed using the AQUACHEM 4.0 software to understand general chemical characteristics and geochemical processes involved. The study reveals that cations, such as sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) and anions, such as bicarbonate (HCO3-), sulphate (SO42-), chloride (Cl-), nitrate (NO3-) are present. Recognition methods such as (a) Box and Whisker diagram (b) Piper diagram (c) Durov diagram (d) Radial plot and (e) Stiff diagram were prepared to delineate the seasonal variations in chemical constituents. The major ionic concentration of the groundwater samples of Peruvanthanam sub-watershed is Mg2+&gt;Ca2+&gt;HCO3-&gt;Cl-&gt;SO42-&gt;NO3-&gt;Na+&gt;K+ and that of Valiyathodu is Mg2+&gt;Ca2+&gt;HCO3-&gt;Cl-&gt;NO3-&gt;SO42-&gt;Na+&gt;K+. A critical analysis of Piper diagram reveals that in Peruvanthanam sub-watershed the pre monsoon groundwater samples belong to the zone of bicarbonates, chloride and sulphates, the monsoon season samples belong to the bicarbonate and chloride zone and the post monsoon samples belong to the zone of prevailing bicarbonates. In Valiyathodu sub-watershed, the pre monsoon and post monsoon samples have dominant bicarbonates, while the monsoon samples show predominance of both bicarbonates and chloride. Radial plots and Stiff diagrams for Peruvanthanam sub-watershed show that Mg2+-Ca2+-HCO3-, Mg2+-Ca2+-Cl- and Mg2+-Ca2+-HCO3-- Cl- are the dominant water types during the pre monsoon season. Mg2+-Ca2+-HCO3--Cl-, Mg2+-Ca2+-Cl-- HCO3- and Mg2+-Ca2+-HCO3--Cl--SO42- are dominant during the monsoon and Mg2+-Ca2+-HCO3- and Mg2+-Ca2+-HCO3--Cl- are the dominant water types during the post monsoon season. In Valiyathodu sub-watershed during the pre monsoon - Mg2+-Ca2+-HCO3--Cl- and Mg2+-Ca2+-HCO3-, during the monsoonm - Mg2+-Ca2+- HCO3--Cl-, Mg2+-Ca2+-Cl-- HCO3- and Ca2+-Mg2+-HCO3--Cl-, and during the post monsoon - Mg2+-Ca2+-HCO3--Cl- and Ca2+-Mg2+-HCO3--Cl- are the dominant water types. DOI: http://dx.doi.org/10.5755/j01.erem.66.4.4037

Identification of surface water-groundwater interaction by hydrogeochemical indicators and assessing its suitability for drinking and irrigational purposes in Chennai, Southern India

Large cities face water quality and quantity problems due to increasing population and improper disposal of solid and liquid wastes. It is essential to monitor the water quality to take corrective measures. This study was carried out in one of the densely populated metropolitan cities in India to ascertain the suitability of groundwater for drinking and irrigation activity, identify the processes controlling the geochemistry of groundwater and the impact of Adyar River on the groundwater quality. Magnesium and pH concentration in groundwater of this area were within the maximum permissible limits of WHO standards. Sodium and potassium concentration of groundwater were greater than the permissible limit in 30.8 % and in 50 % of the samples, respectively. About 35 % of the groundwater samples were not permissible for drinking based on the electrical conductivity (EC). The EC of groundwater was increasing towards the coast. In general, the quality of groundwater for irrigation purpose vary from moderate to good based on Na%, magnesium hazard, residual sodium carbonate, sodium absorption ratio, permeability index, and USDA classification. Na–Cl and Ca–Mg–Cl were the dominant groundwater and surface water type. Increased ionic concentration of groundwater towards the eastern part of the study area is due to the discharge of industrial effluents and domestic sewage into the Adyar River. Seawater intrusion is also one of the reasons for Na–Cl dominant groundwater near the coast. Evaporation and ion exchange were the major processes controlling groundwater chemistry in this area. The groundwater quality of this region is affected by the contaminated surface water.

Evaluation of water quality using geochemical modeling in the Bellary Nala Command area, Belgaum district, Karnataka State, India

The present study aimed at assessment of geochemical composition of 25 water samples to evaluate their suitability for drinking and irrigation purposes in the Bellary Nala command area. Geochemical modeling carried out using PHREEQC program confirmed that majority of the samples in the study area were saturated and/or supersaturated with respect to anhydrite, calcite and gypsum while few were undersaturated with respect to calcite, gypsum, fluorite and halite. From Piper trilinear diagram, Ca2+–Mg2+–HCO3 − was found to be the dominant water type (~68 %), which could be as a result of dissolution of carbonate minerals such as dolomite and calcite prevailing in the study area. However, cation-exchange processes could be responsible for the formation of the Ca2+–Mg2+–Cl−–SO4 2− water type (~32 %) from the CaSO4 and NaCl types, which in turn formed due to the dissolution of anhydrite, gypsum and halite. Wilcox’s and USSL graphical representations showed that majority of the samples belong to good to permissible and high salinity-low sodium (C3S1) category, respectively. Factor analysis concluded that the water quality parameters and saturation indices that are falling under factors 1 and 2 with a strong loading (>75 %) and eigen values (>1) are mainly responsible for controlling the variation in the groundwater chemistry, accounting to 83.3 and 80.72 % of total variance, respectively.

Naturally occurring arsenic in terrestrial geothermal systems of western Anatolia, Turkey: Potential role in contamination of freshwater resources

Arsenic (As) contamination in terrestrial geothermal systems has been identified in many countries worldwide. Concentrations higher than 0.01mg/L are detrimental to human health. We examined potential consequences for As contamination of freshwater resources based on hydrogeochemical investigations of geothermal waters in deep wells and hot springs collected from western Anatolia, Turkey. We analyzed samples for major ions and trace element concentrations. Temperature of geothermal waters in deep wells showed extreme ranges (40 and 230°C), while, temperature of hot spring fluids was up to 90°C. The Piper plot illustrated two dominant water types: Na-HCO3− type for geothermal waters in deep wells and Ca-HCO3− type for hot spring fluids. Arsenic concentration ranged from 0.03 to 1.5mg/L. Dominance of reduced As species, i.e., As(III), was observed in our samples. The Eh value ranged between −250 and 119mV, which suggests diverse geochemical conditions. Some of the measured trace elements were found above the World Health Organization guidelines and Turkish national safe drinking water limits. The variation in pH (range: 6.4–9.3) and As in geothermal waters suggest mixing with groundwater. Mixing of geothermal waters is primarily responsible for contamination of freshwater resources and making them unsuitable for drinking or irrigation.

Hydrochemistry of groundwater in a coastal region and its repercussion on quality, a case study—Thoothukudi district, Tamil Nadu, India

A hydrogeochemical study was conducted in Thoothukudi district situated in the southeast coast of Tamil Nadu, India to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. Scattered studies of this coastal region have reported signs of seawater intrusion, salt pan and industrial activity together with natural weathering process. To have a holistic picture of geochemical processes in the entire district, a total of 135 groundwater samples were collected and analyzed for major cations and anions. The geochemical parameters were compared with world and Indian standards and it was found that most samples are unsuitable for drinking purpose. The geochemical facies of the groundwater showed Na–Cl as the dominant water type indicating the saline nature of the groundwater. Chadda’s plots show that most of the samples fall in the Na–Cl type of water due to seawater intrusion. The samples were classified with parameters like sodium absorption ratio, residual sodium carbonate, total hardness, chloride, index to base exchange, electrical conductivity and facies to determine their suitability for irrigation purpose. It was inferred that the samples falling along the coast are not suitable for the irrigation purpose. The seawater-mixing percentage indicates that strong mixing was observed in the near shore and at the proximity of the salt pan. The permanent hardness was predominant in all the samples compared to the carbonate hardness reducing its domestic usability.

Groundwater composition and pollution due to agricultural practices at Sete Cidades volcano (Azores, Portugal)

Groundwater is a strategic resource of the Azores archipelago given that agriculture is a major economic activity. A field study was undertaken at Sete Cidades volcano (São Miguel, Portugal) to characterize the composition of soil water at several depths in two sites: one without anthropogenic pressure (village site) and the other pasture land (Pa I site), and groundwater in the saturated zone of both sites. The composition of groundwater from springs discharging on the volcano flanks and inside the summit caldera is similar, composed principally of poorly mineralized Na–HCO3 and Na–HCO3–Cl water types, as suggested by median electrical conductivity values. Samples of groundwater collected in seven piezometers spread inside the Sete Cidades caldera are characterized by a conductivity between 95 and 232μS/cm and the dominant water type is Na–HCO3.Soil water at the Sete Cidades village site is of Na–Cl type and its compositional similiarity to rain water suggests control by evapotranspiration. The limited soil depth of the site, as well as the high precipitation and soil hydraulic conductivity, cause vertical homogenization of soil water composition. In contrast, soil water sampled at the pasture site (Pa1) shows greater mineralization when compared to the previous site, and waters are mainly HCO3 to HCO3–Cl types with a Mg–Ca trend for cations. A trend was indicated for the relative soil water composition at site Pa I, from the more superficial suction cup (G1) to the deeper G14–15. This is an evolution similar to perched-water bodies inside the Sete Cidades Caldera. The Mg–Ca-dominated composition at lower depth is explained by the application of fertilizers. Nevertheless, other processes are also influencing water chemistry evolution, and the observed relative decreases in Ca, Mg and K with depth may result from clay formation and the uptake by ion exchange of Ca2+ and Mg2+ for Na+. Although, the relative increase in Na could also result from silicate weathering. Besides contributing to the Na content, silicate dissolution may also explain the relative increase in HCO3, both being associated with silica in solution.The impact of the excessive application of fertilizers is reflected by the NO3 contents of soil water at Pa I and the village sites, as values are higher where agriculture is developed, with a similar trend being observed in the saturated zone.

A preliminary assessment of hydrogeological features and selected anthropogenic impacts on an alluvial fan aquifer system in Greece

An investigation was carried out to delineate the hydrogeologic framework and to understand groundwater quality of the Kompsatos River fan aquifer system, northeastern Greece, as well as to assess environmental impact induced by human activities. As groundwater is the only major source of water in this area, it is important to know the effect of geological formations, and anthropogenic activities on groundwater chemistry and environment. A thorough hydrogeological study was performed during the period 2004–2007. The differential river gauging method was used for estimating the volume of water leaking from (or discharging into) the river. Groundwater samples were collected from 89 monitoring wells, during the summer period of 2007, and analyzed for major ions and trace elements. A potential reservoir of groundwater is formed within the Kompsatos River fan. The aquifer system/Kompsatos River interaction is the outstanding feature of this area. Ca–Mg–HCO3–SO4 is the dominant water type as a result of dissolving carbonate salts. B, Ba, Mn, Li, Sr, and Zn are the most abundant trace elements in groundwater. Both the major-ion chemistry and trace element enrichment of the groundwater are controlled by mineral dissolution and water–rock interaction. Nitrate contamination of groundwater is related to agricultural practices. An improperly constructed drainage system led locally to salinization of groundwater. Channelization has caused considerable disruption to the river ecosystem. The eventual construction of a dam on the river will adversely affect the environment and the aquifer system. The lack of managerial policy for water is putting environmental resources and water supply in jeopardy.

Evaluation of groundwater quality and its suitability for drinking and agricultural use in the coastal stretch of Alappuzha District, Kerala, India

Groundwater is an essential and vital component of any life support system. It is not only the basic need for human existence but also a vital input for all development activities. The present hydro-geochemical study was confined to the coastal belt of Alappuzha district, which lies in the coastal lowland division of Kerala. Groundwater quality and its suitability for irrigation and domestic purpose were examined by various physico-chemical parameters such as pH, electrical conductivity, total dissolved solids, total hardness, calcium, magnesium, sodium, potassium, bicarbonate, sulfate, and chloride. These parameters were used to assess the suitability of groundwater for domestic purpose by comparing with the WHO and Indian standards. TDS, sodium adsorption ratio (SAR), and permeability index were used for irrigation suitability assessment. The sample analysis reveals that the groundwater is not entirely fit for drinking with respect to pH, EC, Ca2+, Mg2+, Na+, and Cl−. In some of the collected samples, the concentrations of these parameters exceed the permissible limits of WHO and ISI standards. Based on TDS and SAR almost all samples are suitable for irrigation purpose except a few locations, which show values beyond the permissible limits. Ca–Mg–HCO3 is the dominant water type in the study area. The sequence of the abundance of the major cations and anions is Ca > Na > Mg > K = HCO3 > Cl > SO4. Based on the total hardness and TDS, 96 % of groundwater samples are found suitable for drinking purpose.