Hydrochemical appraisal of groundwater and its suitability in the intensive agricultural area of Muzaffarnagar district,Uttar Pradesh,India

Muzaffarnagar is an economically rich district situated in the most fertile plains of two great rivers Ganga and Yamuna in the Indo-gangetic plains, with agricultural land irrigated by both surface water as well as groundwater. An investigation has been carried out to understand the hydrochemistry of the groundwater and its suitability for irrigation uses. Groundwater in the study area is neutral to moderately alkaline in nature. Chemistry of groundwater suggests that alkaline earths (Ca + Mg) significantly exceed the alkalis (Na + K) and weak acids exceed the strong acids (Cl + SO₄), suggesting the dominance of carbonate weathering followed by silicate weathering. Majority of the groundwater samples (62%) posses Ca–Mg–HCO₃ type of hydrochemical species, followed by Ca–Na–Mg–HCO₃, Na–Ca–Mg–HCO₃, Ca–Mg–Na–HCO₃–Cl and Na–Ca–HCO₃–SO₄ types. A positive high correlation (r ² = 0.928) between Na and Cl suggests that the salinity of groundwater is due to intermixing of two or more groundwater bodies with different hydrochemical compositions. Barring a few locations, most of the groundwater samples are suitable for irrigation uses. Chemical fertilizers, sugar factories and anthropogenic activities are contributing to the sulphate and chloride concentrations in the groundwater of the study area. Overexploitation of aquifers induced multi componential mixing of groundwater with agricultural return flow waters is responsible for generating groundwater of various compositions in its lateral extent.     

Hydrochemical and isotopic study of groundwater in the Yinchuan plain, China

The Yinchuan plain is located in the arid climate zone of NW China. The western margin of the plain is the Helan mountain connecting a series of normal slip faults. The eastern margin of the plain connects with the Yellow River and adjacents with the Ordos platform. The south of the plain is bordered by the EN fault of the Niushou mountain. The bottom of the plain is the Carboniferous, Permian, or Ordovician rocks. Based on the analysis of groundwater hydrochemical and isotopic indicators, this study aims to identify the groundwater recharge and discharge in the Yinchuan plain, China. The hydrochemical types of the groundwater are HCO₃–SO₄ in the west, HCO₃–Cl in the middle, and Cl–SO₄ in the east. The hydrochemical types are HCO₃–SO₄ in the south, HCO₃–Cl and SO₄–HCO₃ in the middle. The hydrochemical types are complex in the north, mainly SO₄–HCO₃ and Cl–SO₄. Deuterium, ¹⁸O, and tritium values of groundwater indicate that groundwater recharge sources include precipitation, bedrock fissure water, and irrigation return water. Groundwater discharges include evaporation, abstraction, and discharge to surface water. According to the EW isotopic profile, the groundwater flow system (GFS) in the Yinchuan plain can be divided into local flow systems (LFS) and regional flow systems (RFS). Groundwater has lower TDS and higher tritium in the southern Yellow River alluvial plain and groundwater age ranges from 6 to 25 years. The range of groundwater renewal rates is from 11 to 15 % a^?1. The depth of the water cycle is small, and groundwater circulates fast and has high renewal rates. Groundwater has higher TDS and lower tritium in the northern Yellow River alluvial plain. The range of groundwater age is from 45 to 57 years, and renewal rate is from 6 to 0.1 % a^?1. The depth of the water cycle is larger. Groundwater circulates slowly and has low renewal rates.     

Ionic exchange in groundwater hydrochemical evolution. Study case: the drainage basin of El Pescado creek (Buenos Aires province,Argentina)

The phreatic aquifer beneath the Pampean plain, in eastern central Argentina, constitutes a relevant source of water supply in the area. The objective of this work was to assess the significance of the cation exchange processes in the hydrochemical evolution of this aquifer, based on a study case located in the middle and upper basin of the El Pescado creek. Results indicate that Ca²⁺/Na⁺ exchange is the main process determining the evolution of groundwater from the recharge areas (Ca–HCO₃) towards the local discharge areas (Na–HCO₃), as well as representing a source of Na⁺ contribution to the water in the aquifer. This hydrochemical characteristic is central to the identification of local discharge areas within a plain environment which extends regionally. The ion exchange capacity of these discharge areas has environmental importance, due to its influence on groundwater quality and potential groundwater uses. These results may be applied to any aquifer sharing similar hydrogeological characteristics.     

Chemical evolution in the high arsenic groundwater of the Huhhot basin (Inner Mongolia,PR China) and its difference from the western Bengal basin (India)

Elevated As concentrations in groundwater of the Huhhot basin (HB), Inner Mongolia, China, and the western Bengal basin (WBB), India, have been known for decades. However, few studies have been performed to comprehend the processes controlling overall groundwater chemistry in the HB. In this study, the controls on solute chemistry in the HB have been interpreted and compared with the well-studied WBB, which has a very different climate, physiography, lithology, and aquifer characteristics than the HB. In general, there are marked differences in solute chemistry between HB and WBB groundwaters. Stable isotopic signatures indicate meteoric recharge in the HB in a colder climate, distant from the source of moisture, in comparison to the warm, humid WBB. The major-ion composition of the moderately reducing HB groundwater is dominated by a mixed-ion (Ca–Na–HCO₃–Cl) hydrochemical facies with an evolutionary trend along the regional hydraulic gradient. Molar ratios and thermodynamic calculations show that HB groundwater has not been affected by cation exchange, but is dominated by weathering of feldspars (allitization) and equilibrium with gibbsite and anorthite. Mineral weathering and mobilization of As could occur as recharging water flows through fractured, argillaceous, metamorphic or volcanic rocks in the adjoining mountain-front areas, and deposits solutes near the center of the basin. In contrast, WBB groundwater is Ca–HCO₃-dominated, indicative of calcite weathering, with some cation exchange and silicate weathering (monosiallitization).     

Geochemical evolution of groundwater in carbonate aquifers in Taiyuan, northern China

Thirty-nine samples of both cold and thermal karst groundwater from Taiyuan, northern China were collected and analyzed with the aim of developing a better understanding of the geochemical processes that control the groundwater quality evolution in the region’s carbonate aquifers. The region’s karst groundwater system was divided into three geologically distinct sub-systems, namely, the Xishan Mountain karst groundwater subsystem (XMK), the Dongshan Mountain karst groundwater subsystem (DMK) and the Beishan Mountain karst groundwater subsystem (BMK). Hydrochemical properties of the karst groundwaters evolve from the recharge zones towards the cold water discharge zones and further towards the thermal water discharge zones. In the XMK and the DMK, the hydrochemical type of the groundwater evolves from HCO₃-Ca·Mg in the recharge - flow-through zone, to HCO₃·SO₄-Ca·Mg/SO₄·HCO₃-Ca·Mg in the cold water discharge zone, and further to SO₄-Ca·Mg in the thermal water discharge zone. By contrast, the water type changes from HCO₃-Ca·Mg to HCO₃·SO₄-Ca·Mg in the BMK, with almost invariable TDS and temperatures all along from the recharge to the discharge zone. The concentrations of Sr, Si, Fe, F⁻ and of some trace elements (Al, B, Li, Mn, Mo, Co, Ni) increase as groundwater temperature increases. Different hydrogeochemical processes occur in the three karst groundwater sub-systems. In the XMK and the DMK, the geochemical evolution of the groundwater is jointly controlled by carbonate dissolution/precipitation, gypsum dissolution and dedolomitization, while only calcite and dolomite dissolution/precipitation occurs in the BMK without dedolomitization. The hydrogeochemical data of the karst groundwaters were used to construct individual geochemical reaction models for each of the three different karst groundwater sub-systems. The modeling results confirm that dedolomization is the major process controlling hydrochemical changes in the XMK and the DMK. In the thermal groundwaters, the dissolution rates of fluorite, siderite and strontianite were found to exceed those of the cold karst groundwater systems, which can explain the higher concentrations of F⁻, Fe and Sr²⁺ that are found in these waters.     

Integrated hydrochemical assessment of the Quaternary alluvial aquifer of the Guadalquivir River, southern Spain

The alluvial aquifer of the Guadalquivir River comprises shallow Quaternary deposits located in the central-eastern part of the Province of Jaén in southern Spain, where groundwater resources are used mainly for crop irrigation in an important agricultural area. In order to establish the baseline hydrochemical conditions and processes determining the groundwater quality, groundwater and river water samples were collected as part of an integrated investigation that coupled multivariate statistical analysis with hydrochemical methods to identify and interpret the groundwater chemistry of the aquifer system. Three main hydrochemical types (Mg–Ca–HCO₃, Ca–Mg–SO₄–HCO₃–Cl and Na–Ca–Mg–Cl–SO₄) were identified. Further interpretation, using R-mode principal components analysis (PCA) conducted with 13 hydrochemical variables, identified two principal components which explain ⅔ of the variance in the original data. In combination with the hydrochemical interpretation, mineralogical analyses of the aquifer sediment together with inverse geochemical modelling using NETPATH showed that dedolomitization (calcite precipitation and dolomite dissolution driven by gypsum dissolution) is the principal hydrochemical process controlling the regional groundwater chemistry. Other processes such as silicate weathering, ion exchange, mixing between river water and groundwater, and agricultural practices also affect the groundwater chemistry.     

Groundwater geochemistry in the Meshkinshahr basin of Ardabil province in Iran

The chemical analysis of 59 water wells in Meshkinshar area, Ardabil province NW of IRAN has been evaluated to determine the hydrogeochemical processes and ion concentration background in the region. The dominated hydrochemical types are Na–SO₄, Ca–HCO₃, Na–HCO₃ and Na–Cl in the whole area. Based on the total hardness, the groundwater is soft. According to electrical conductivity and sodium adsorption ratio, the most dominant classes are C1–S1, C2–S1 and C3–S1. The major ion concentrations are below the acceptable level for drinking water. The groundwater salinity hazard is medium to high but the Na hazard is low to medium and in regard of irrigation water the quality is low to medium. So the drainage system is necessary to avoid the increase of toxic salt concentrations.     

Hydrochemical evolution and water quality along the groundwater flow path in the Sandıklı plain, Afyon, Turkey

 An unconfined aquifer system suggests an open system in the study area. Hydrochemical evolution is related to the flow path of groundwater. The groundwaters are divided into two hydrochemical facies in the study area, 1) Ca–Mg–HCO₃ and 2) Ca–Mg–SO₄HCO₃. Facies 1 has shallow (young) waters which dominate in recharge areas during rapid flow conditions, whereas facies 2 may show shallow and mixed waters which dominate intermediate or discharge areas during low flow conditions. Ionic concentrations, TDS, EC and water quality are related to groundwater residence time and groundwater types. The groundwaters in the plain are chemically potable and suitable for both domestic and agricultural purposes. Received: 20 May 1996 · Accepted: 30 July 1996     

Hydrochemical baseline condition of groundwater at the Mizunami underground research laboratory (MIU)

Hydrochemical conditions up to depths of 1000 m below ground level around the Mizunami Underground Research Laboratory were investigated to construct a “baseline condition model” describing the undisturbed hydrochemical environment prior to excavation of the underground facilities at Mizunami, Gifu, Japan. Groundwater chemistry in this area was classified into a Na–Ca–HCO₃ type of groundwater in the upper part of sedimentary rock sequence and a Na–(Ca)–Cl type of groundwater in the deeper part of the sedimentary rock sequence and basement granite. The residence time of the groundwaters was estimated from their ¹⁴C contents to be approximately 9.3 ka in the middle part of the sedimentary rock and older than 50 ka in the deep part of the granite. The evolution processes of these groundwaters were inferred to be water–rock interactions such as weathering of plagioclase, dissolution of marine sulphate/sulphide minerals and carbonate minerals in the Na–Ca–HCO₃ type of groundwater, and mixing between “low-salinity water” in the shallow part and “higher-salinity water” in the deeper part of the granite in the Na–(Ca)–Cl type of groundwater. The source of salinity in the deeper part of the granite was possibly a palaeo-hydrothermal water or a fossil seawater that recharged in the Miocene, subsequently being modified by long-term water–rock interaction. The Cl-depth trend in granitic groundwater changes at a depth of −400 m below sea level. The hydrogeological properties controlling the groundwater flow and/or mixing processes such as advection and diffusion were inferred to be different at this depth in the granite. This hydrochemical conceptual model is indispensable not only when constructing the numerical model for evaluating the hydrochemical disturbance during construction and operation of the MIU facility, but also when confirming a hydrogeological model.     

Groundwater hydrochemistry of a sugarcane cultivation belt in parts of Muzaffarnagar district, Uttar Pradesh, India

The Kali-Hindon is a watershed in the most productive central Ganga plain of India. The whole area is a fertile track with sugarcane being the principal crop. Systematic sampling was carried out to assess the source of dissolved ions, impact of sugar factories and the quality of groundwater. Thirty-six samples were collected covering an area of 395 km². The quality of groundwater is suitable for irrigational purposes but is rich in SO₄ which is not best for human consumption. Graphical treatment of major ion chemistry helps identify six chemical types of groundwater. All possible species such as Na–Cl, K–Cl, Na–HCO₃, Na–SO₄, Ca–HCO₃, Mg–HCO₃, Ca–SO₄ and Mg–SO₄ are likely to occur in the groundwater system. The most conspicuous change in chemistry of groundwater is relative enrichment of SO₄. The interpretation of data reveals that SO₄ has not been acquired through water–rock interaction. The source of SO₄ is anthropogenic. Sugar factories alone are responsible for this potential environmental hazard.     

Hydro-environmental status and soil management of the River Nile Delta,Egypt

The sea level rise has its own-bearing on the coastal recession and hydro-environmental degradation of the River Nile Delta. Attempts are made here to use remote sensing to detect the coastal recession in some selected parts and delineating the chemistry of groundwater aquifers and surface water, which lie along south-mid-northern and coastal zone of the Nile Delta. Eight water samples from groundwater monitoring wells and 13 water samples from surface water were collected and analyzed for various hydrochemical parameters. The groundwater samples are classified into five hydrochemical facies on Hill-Piper trilinear diagram based on the dominance of different cations and anions: facies 1: Ca–Mg–Na–HCO₃–Cl–SO₄ type I; facies 2: Na–Cl–HCO₃ type II; facies 3: Na–Ca–Mg–Cl type III, facies 4: Ca–Na–Mg–Cl–HCO₃ type IV and facies 5: Na–Mg–Cl type V. The hydrochemical facies showed that the majority of samples were enriched in sodium, bicarbonate and chloride types and, which reflected that the sea water and tidal channel play a major role in controlling the groundwater chemical composition in the Quaternary shallow aquifers, with a severe degradation going north of Nile Delta. Also, the relationship between the dissolved chloride (Cl, mmol/l), as a variable, and other major ion combinations (in mmol/l) were considered as another criterion for chemical classification system. The low and medium chloride groundwater occurs in southern and mid Nile Delta (Classes A and B), whereas the high and very high chloride (classes D and C) almost covers the northern parts of the Nile Delta indicating the severe effect of sea water intrusion. Other facets of hydro-environmental degradation are reflected through monitoring the soil degradation process within the last two decades in the northern part of Nile Delta. Land degradation was assessed by adopting new approach through the integration of GLASOD/FAO approach and Remote Sensing/GIS techniques. The main types of human induced soil degradation observed in the studied area are salinity, alkalinity (sodicity), compaction and water logging. On the other hand, water erosion because of sea rise is assessed. Multi-dates satellite data from Landsat TM and ETM+ images dated 1983 and 2003 were used to detect the changes of shoreline during the last two decades. The obtained results showed that, the eroded areas were determined as 568.20 acre; meanwhile the accreted areas were detected as 494.61 acre during the 20-year period.     

Recharge source and hydrogeochemical evolution of shallow groundwater in a complex alluvial fan system,southwest of North China Plain

Many cities around the world are developed at alluvial fans. With economic and industrial development and increase in population, quality and quantity of groundwater are often damaged by over-exploitation in these areas. In order to realistically assess these groundwater resources and their sustainability, it is vital to understand the recharge sources and hydrogeochemical evolution of groundwater in alluvial fans. In March 2006, groundwater and surface water were sampled for major element analysis and stable isotope (oxygen-18 and deuterium) compositions in Xinxiang, which is located at a complex alluvial fan system composed of a mountainous area, Taihang Mt. alluvial fan and Yellow River alluvial fan. In the Taihang mountainous area, the groundwater was recharged by precipitation and was characterized by Ca–HCO₃ type water with depleted δ¹⁸O and δD (mean value of −8.8‰ δ¹⁸O). Along the flow path from the mountainous area to Taihang Mt. alluvial fan, the groundwater became geochemically complex (Ca–Na–Mg–HCO₃–Cl–SO₄ type), and heavier δ¹⁸O and δD were observed (around −8‰ δ¹⁸O). Before the surface water with mean δ¹⁸O of −8.7‰ recharged to groundwater, it underwent isotopic enrichment in Taihang Mt. alluvial fan. Chemical mixture and ion exchange are expected to be responsible for the chemical evolution of groundwater in Yellow River alluvial fan. Transferred water from the Yellow River is the main source of the groundwater in the Yellow River alluvial fan in the south of the study area, and stable isotopic compositions of the groundwater (mean value of −8.8‰ δ¹⁸O) were similar to those of transferred water (−8.9‰), increasing from the southern boundary of the study area to the distal end of the fan. The groundwater underwent chemical evolution from Ca–HCO₃, Na–HCO₃, to Na–SO₄. A conceptual model, integrating stiff diagrams, is used to describe the spatial variation of recharge sources, chemical evolution, and groundwater flow paths in the complex alluvial fan aquifer system.     

Groundwater hydrochemistry and origin in the south-eastern part of Wadi El Natrun,Egypt

The demand for water is rapidly increasing in Egypt, because of high population and agriculture production growth rate, which makes research of water resources necessary. The regional multi-aquifer system of the Miocene–Pleistocene age is discharged in Wadi El Natrun area. Intensive aquifer overexploitation and agricultural development in the area are related to groundwater quality deterioration. Hydrochemical and hydrogeological data was evaluated to determine the groundwater origin and quality in the south-eastern part of wadi, which appears to be more significant for water supply owing to lower groundwater salinity. The dominance of the high mineralised Cl groundwater type was found; however, also less mineralised SO₄ and HCO₃ types were identified there. Based on the ion relations, halite and gypsum dissolution and ion exchange are the most important hydrochemical processes forming the groundwater chemical composition. The Cl dominated groundwater matches the discharge part of the regional hydrogeological system. Contrary, the presence of HCO₃ and SO₄ hydrochemical types corresponds to the infiltration and transferring parts of the hydrogeological system indicating the presence of zones conducting low mineralised groundwater. The discharge area of the over-pumped aquifer in Wadi El-Natrun lies 23 m beneath the sea level with the shoreline being at the distance of 100 km, thus there is a real risk of seawater intrusion. Using the hydrochemical facies evolution diagram, four samples in the centre of the discharge area indicate advanced seawater intrusion. The zones of the highest demand for groundwater quality protection were indicated based on a spatial pattern of hydrogeochemical composition.     

Study on the dynamic characteristics of groundwater in the valley plain of Lhasa City

The valley plain of Lhasa City is located on the Qinghai-Tibetan Plateau, which is one of the most developed and densely populated areas in Tibet. Groundwater is an important water supply source and plays an irreplaceable role in the social and economic development of Lhasa City. This study has investigated the dynamic characteristics of groundwater in the valley plain of Lhasa City through the methods of mathematical statistics and hydrochemical analysis. The results showed that local topography, climate, and urbanization substantially influenced the groundwater dynamics. Under the combined influences from urbanization and climate, the groundwater level decreased over three time periods, but the groundwater-level configuration has not shown significant changes in over 15 years. From 1997 to 2015, the hydrochemical type of groundwater has changed from HCO₃–Ca to HCO₃·SO₄–Ca·Mg and HCO₃·SO₄–Ca. The concentrations of Cl^?, Mg²⁺, and SO₄^2? in groundwater increased, but the concentrations of other ions were relatively stable. Water–rock interaction was the main mechanism controlling the groundwater chemistry in the study area, and it was mainly associated with the dissolution of silicate, carbonate, and halite.     

Application of hydrochemical signatures to delineating portable groundwater resources in Ordos Basin, China

The Ordos Basin of China encompasses Shaanxi, Gansu, and Shanxi provinces, Ningxia and Inner Mongolia autonomous regions. It lacks significant surface water resources. Among the water-bearing formations, the Luohe formation, with an area of 1.32×10⁵ km², is the most prospective aquifer. Groundwater quality data collected at 211 boreholes drilled into the Luhe formation indicate a complex distribution of groundwater chemistry. The hydrochemical properties were used to study the recharge, runoff, and discharge conditions of the groundwater in Ordos Basin and to evaluate sustainable groundwater resources. In the northern part of the basin, the hydrochemistry types and the total dissolved solids (TDS) show a clear lateral transition from SEE to NWW, indicating that the groundwater gets recharge in the northwest region and discharges in the southeast region. In the southern part of the basin, maximum TDS occurs at the center of the Malian River valley, from which the TDS decreases radially. Therefore, the groundwater in the southern basin gets recharge from the southeast and southwest regions, and the Malian River valley is the discharge zone. As a result of this research, the areas with portable groundwater were delineated. They include most of the southeast region of the Sishili Ridge, east of the Ziwu Mountain, and the southwest corner of the basin. The TDS of the groundwater in these regions is less than 1 g/l, and the hydrochemistry type is either HCO₃ or HCO₃·SO₄.     

Statistical categorization geochemical modeling of groundwater in Ain Azel plain (Algeria)

Water analysis data of 54 groundwater samples from 18 uniformly distributed wells were collected during three campaigns (June, September and December 2004). Q-mode hierarchical cluster analysis (HCA) was employed for partitioning the water samples into hydrochemical facies. Interpretation of analytical data showed that the abundance of major ions was identified as follows: Ca ? Mg > Na > K and HCO₃ ? Cl > SO₄. Three major water facies are suggested by the HCA analysis. The samples from the area were classified as recharge area waters (Ca–Mg–HCO₃ water), transition area waters (Mg–Ca–HCO₃–Cl water), and discharge area waters (Mg–Ca–Cl–HCO₃ water). Inverse geochemical modeling suggests that relatively few phases are required to derive the water chemistry in the area. In a broad sense, the reactions responsible for the hydrochemical evolution in the area fall into two categories: (1) evaporite weathering reactions and (2) precipitation of carbonate minerals.     

Hydrochemical and isotopic characteristics of groundwater in the Yanqi Basin of Xinjiang province, northwest China

In this study, hydrochemical and isotope investigations were conducted in the Yanqi Basin to determine the chemical composition, and to gain insight into the groundwater recharge process in the Yanqi Basin. It mainly used hydrochemistry, environmental isotopes, and a series of comprehensive data interpretation, e.g., statistics, ionic ratios, and Piper diagram to obtain a better understanding of the functioning of the system. The following hydrochemical processes were identified as the main factors controlling the water quality of the groundwater system: weathering of silicate minerals, dissolution, ion exchange, and to a lesser extent, evaporation, which seemed to be more pronounced down gradient of the flow system. As groundwater flows from the recharge to discharge areas, chemical patterns evolve in the order of Ca²⁺–HCO₃ ^?, Ca²⁺/Mg²⁺–HCO₃ ^? to Ca²⁺–Mg²⁺–Cl^?–SO₄ ^2?, Na⁺–K⁺–Cl^?–SO₄ ^2? and Na⁺–Cl^? according to lithology. The environmental isotope (δ ¹⁸O, δ ²H, ³H) measurements further revealed that precipitation was the main recharge source for the groundwater system; some local values indicated high levels of evaporation. Tritium and CFC analysis were used to estimate the ages of the different groundwater; the tritium values of the groundwater samples varied from 2.82 to 29.7 TU. The age of the groundwater at depths of <120 m is about 30–50 years. CFC values obtained for six samples to determine groundwater age; the age of the groundwater is about 20–50 years.     

Principal component and multivariate statistical approach for evaluation of hydrochemical characterization of fluoride-rich groundwater of Shaslar Vagu watershed,Nalgonda District,India

In order to assess the impact of fluoride-rich groundwater of Shasilair Vagu watershed on groundwater regime, more than hundred groundwater samples for pre- and post-monsoon seasons were collected from bore wells/dug wells and analyzed for major ions. Water quality analysis of major ion chemistry shows elevated concentration of fluoride in groundwater samples. The fluoride concentration ranges from 1.4 to 5.9 mg/l and 1.5 to 5.8 mg/l in pre- and post-monsoons, respectively. The result clearly shows that the seasonal variation of fluoride in groundwater is due to recharge of rain water during monsoon. The water quality data was analyzed by hydrochemical facies (Piper diagram), Gibbs plot, and various plots. Plots of Na versus Cl, Ca versus SO₄, and (Na+Cl)-(SO₄+HCO₃) versus (Na+K-Cl) shows positive and negative values, indicating that their source of high concentration are aquifer, evapotranpiration, and other anthropogenic sources. Saturation index of halite and gypsum shows that all groundwater samples were undersaturated and suggests that carbonate minerals influence the concentration. Using multivariate statistical techniques, viz., principal component (factor analysis and cluster analysis), the analysis brought out impact of intensity of excess use of fertilizers and excess withdrawal of groundwater regime. Multivariate statistical techniques are potential tools and provide greater precision for identifying contaminant parameter linkages.     

Hydrogeochemical and isotopic evidences of the groundwater regime in Datong Basin, Northern China

Datong Basin is one of the Cenozoic faulted basins in Northern China’s Shanxi province, where groundwater is the major source of water supply. The results of hydrochemical investigation show that along the groundwater flow path, from the margins to the lower-lying central parts of the basin, groundwater generally shows increases in concentrations of TDS, HCO₃ ^?, SO₄ ^2?, Cl^?, Na⁺ and Mg²⁺ (except for Ca²⁺ content). Along the basin margin, groundwater is dominantly of Ca–HCO₃ type; however, in the central parts of the basin it becomes more saline with Na–HCO₃-dominant or mixed-ion type. The medium-deep groundwater has chemical compositions similar to those of shallow groundwater, except for the local area affected by human activity. From the mountain front to the basin area, shallow groundwater concentrations of major ions increase and are commonly higher than those in medium-deep aquifers, due to intense evapotranspiration and anthropogenic contamination. Hydrolysis of aluminosilicate and silicate minerals, cation exchange and evaporation are prevailing geochemical processes occurring in the aquifers at Datong Basin. The isotopic compositions indicate that meteoric water is the main source of groundwater recharge. Evaporation is the major way of discharge of shallow groundwater. The groundwater in medium-deep aquifers may be related to regional recharges of rainwater by infiltrating along the mountain front faults, and of groundwater permeating laterally from bedrocks of the mountain range. However, in areas of groundwater depression cones, groundwater in the deep confined aquifers may be recharged by groundwater from the upper unconfined aquifer through aquitards.     

Evaluation of groundwater quality in coastal areas: implications for sustainable agriculture

Seawater intrusion is a problem in the coastal areas of Korea. Most productive agricultural fields are in the western and southern coastal areas of the country where irrigation predominantly relies on groundwater. Seawater intrusion has affected agricultural productivity. To evaluate progressive encroachment of saline water, the Korean government established a seawater intrusion monitoring well network, especially in the western and southern part of the peninsula. Automatic water levels and EC monitoring and periodic chemical analysis of groundwater help track salinization. Salinization of fresh groundwater is highly associated with groundwater withdrawal. A large proportion of the groundwaters are classified as Na–Cl and Ca–Cl types. The Na–Cl types represent effects of seawater intrusion. The highest EC level was over 1.6 km inland and high Cl values were observed up to 1.2 km inland. Lower ratios of Na/Cl and SO₄/Cl than seawater values indicate the seawater encroachment. A linear relation between Na and Cl represents simple mixing of the fresh groundwater with the seawater. The saline Na–Cl typed groundwaters showed Br/Cl ratios similar to or less than seawater values. The Ca–HCO₃ type groundwaters had the highest Br/Cl ratios. Substantial proportions of the groundwaters showed potential for salinity and should be better managed for sustainable agriculture.