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.     

The hydrochemical facies and anomalous fluoride content in the Serra Geral aquifer system,southern Brazil: a GIS approach with tectonic and principal component analysis

Groundwater with high fluoride content and water mixture patterns were studied in Serra Geral aquifer system (SGAS) using three aspects, principal component analysis (PCA), tectonic scenery and hydrochemical interpretation from 309 groundwater chemical data information from deep wells. A four-component model is suggested and explains 81% of total variance in the PCA. Six hydrochemical facies were identified. These facies suggest two different fluoride sources. Tectonic approach shows the relationship between defined hydrochemical facies and regional fracture control. The applied methodology reveals a minimum level to understand hydrochemical mixtures. The fluoride enrichment mechanisms into the groundwater are comprised in advance to guide the future uses of SGAS to the public supply.     

Groundwater components in the alluvial aquifer of the alpine Rhone River valley, Bois de Finges area, Wallis Canton, Switzerland

Source, type, and quantity of various components of groundwater, as well as their spatial and temporal variations were determined by different hydrochemical methods in the alluvial aquifer of the upper Rhone River valley, Bois de Finges, Wallis Canton, Switzerland. The methods used are hydrochemical modeling, stable-isotope analysis, and chemical analysis of surface water and groundwater. Sampling during high- and low-water periods determined the spatial distribution of the water chemistry, whereas monthly sampling over three years provided a basis for understanding seasonal variability. The physico-chemical parameters of the groundwater have spatial and seasonal variations. The groundwater chemical composition of the Rhone alluvial aquifer indicates a mixing of weakly mineralized Rhone River water and SO₄-rich water entering from the south side of the valley. Temporal changes in groundwater chemistry and in groundwater levels reflect the seasonal variations of the different contributors to groundwater recharge. The Rhone River recharges the alluvial aquifer only during the summer high-water period. Electronic Publication     

The hydrogeochemical characterization of Morsott-El Aouinet aquifer, Northeastern Algeria

A study of the hydrogeochemical processes in the Morsott-El Aouinet aquifer was carried out with the objective of identifying the geochemical processes and their relation with groundwater quality as well as to get an insight into the hydrochemical evaluation of groundwater. The high salinity coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies as well as future exploitation. A combined hydrogeologic and isotopic investigation have been carried out using chemical and isotopic data to deduce a hydrochemical evaluation of the aquifer system based on the ionic constituents, water types, hydrochemical facies and factors controlling groundwater quality. The ionic speciation and mineral dissolution/precipitation was calculated by WATEQF package software. The increase in salinity is related to the dissolution and/or precipitation processes during the water–rock interaction and to the cationic exchange reactions between groundwater and clay minerals. The isotopic analysis of some groundwater samples shows a similarity with the meteoric waters reflect their short residence time and a lowest evaporation phenomenon of infiltrated groundwater.     

Integration of geoelectric and hydrochemical approaches for delineation of groundwater potential zones in alluvial aquifer

Geoelectric and hydrochemical approaches are employed to delineate the ground-water potential zones in District Okara, a part of Bari Doab, Punjab, Pakistan. Sixty-seven VES surveys are conducted with the Electrical Resistivity Meter. The resultant resistivity verses depth model for each site is estimated using computer-based software IX1D. Aquifer thickness maps and interpreted resistivity maps were generated from interpreted VES results. Dar-Zarrouk parameters, transverse resistance (TR), longitudinal conductance (SL) and anisotropy (λ) were also calculated from resistivity data to delineate the potential zones of aquifer. 70% of SL value is ≤3S, 30% of SL value is > 3S. According to SL and TR values, the whole area is divided into three potential zones, high, medium and low potential zones. The spatial distribution maps show that north, south and central parts of study area are marked as good potential aquifer zones. Longitudinal conductance values are further utilized to determine aquifer protective capacity of area. The whole area is characterized by moderate to good and up to some extent very good aquifer protective area on the basis of SL values. The groundwater samples from sixty-seven installed tube wells are collected for hydro-chemical analysis. The electrical conductivity values are determined. Correlation is then developed between the EC (μS/cm) of groundwater samples vs. interpreted aquifer resistivity showing R2 value 0.90.     

Hydrochemistry and salt-water intrusion in the Van aquifer,east Turkey

Groundwater in the Van coastal aquifer is one of the main sources of potable, industrial and irrigational water in Van City, because of its semi-arid climate. Groundwater extraction has been in excess of replenishment owing to increased agricultural and economic activities and a growing population during the last 20 years. A hydrochemical survey of the Van aquifer provided data on the groundwater chemistry patterns and the main mineralization processes. The main processes influencing the groundwater chemistry are salinisation from salt-water intrusion, silicate mineral dissolution, cation exchange and human activity. Deterioration in water quality has resulted from intrusion of the salt water of Lake Van along the coastal regions into the Van plain. At present, the mixing rate of salt water in the Van aquifer is between 1 and 5.5% and salt water has already invaded about 5 km inland in the iskele and the airport region.     

Groundwater and surface-water interactions in a confined alluvial aquifer between two rivers: effects of groundwater flow dynamics on high iron anomaly

In a confined alluvial aquifer located between two rivers, discrete zones of anomalously high concentrations of redox species such as iron, are thought to be a result of groundwater flow dynamics rather than a chemical evolution along continuous flow paths. This new hypothesis was confirmed at a study site located between Nan and Yom rivers in Phitsanulok, Thailand, by analyzing concentrations of redox species in comparison with dynamic groundwater flow patterns. River incision into the confined alluvial aquifer and seasonally varying river stages result in truncated flow paths. The groundwater flow dynamics between two rivers has four phases that are cyclic, including: aquifer discharge into both rivers, direct flow from one river toward another, aquifer recharge from both rivers, and reverse of river-to-river flow. The resulting groundwater flow direction has a zigzag pattern and its general trend is almost parallel to the river flow. High iron anomaly appears as discrete zones in the transition areas of the confined alluvial aquifer because the lateral recharge from rivers penetrates into the aquifer only by tens of meters. The high iron anomaly, which is nearly constant in space and time, is a result of groundwater/surface-water interactions and related groundwater flow dynamics.     

Study of hydrogeochemical processes of the groundwater in Ghatprabha river sub-basin, Bagalkot District, Karnataka, India

The alluvial aquifer of the Ghatprabha River comprises shallow tertiary sediment deposits underlain by peninsular gneissic complex of Archean age, located in the central–eastern part of the Karnataka in southern India. In order to establish the baseline hydrochemical conditions and processes determining the groundwater quality, groundwater 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 (Ca–Mg–Cl, Ca–Mg–HCO₃, and Na–SO₄) were identified. Gibbs plots indicate that the evolution of water chemistry is influenced by water–rock interaction followed by evapotranspiration process. The results of factor analysis indicated the total variance explained by the extracted factor 79.9% and 87.1% for both pre- and post-monsoon, respectively. And other processes such as silicate weathering, ion exchange, and local anthropogenic activities affect the groundwater chemistry.     

Delineation of groundwater provenance in a coastal aquifer using statistical and isotopic methods,Southeast Tanzania

Rapid population growth and urbanization has placed a high demand on freshwater resources in southeast costal Tanzania. In this paper, we identify the various sources of groundwater and the major factors affecting the groundwater quality by means of multivariate statistical analyses, using chemical tracers and stable isotope signatures. The results from hierarchical cluster analyses show that the groundwater in the study area may be classified into four groups. A factor analysis indicates that groundwater composition is mainly affected by three processes, accounting for 80.6% of the total data variance: seawater intrusion, dilution of groundwater by recharge, and sewage infiltration. The hydrochemical facies of shallow groundwater was mostly of the Na–Ca–Cl type, although other water types were also observed. The deep groundwater samples were slightly to moderately mineralized and they were of the NaHCO₃ type. This water type is induced mainly by dissolution of carbonate minerals and modified by ion exchange reactions. The signal from the stable isotope composition of the groundwater samples corresponded well with the major chemical characteristics. In the shallow groundwater, both high-nitrate and high-chloride concentrations were associated with localized stable isotope enrichments which offset the meteoric isotopic signature. This is inferred to be due to the contamination by influx of sewage, as well as intrusion by seawater. The depleted stable isotope values, which coincides with a chemical signature for the deep aquifer indicates that this deep groundwater is derived from infiltration in the recharge zone followed by slow lateral percolation. This study shows that a conceptual hydrogeochemical interpretation of the results from multivariate statistical analysis (using HCA and FA) on water chemistry, including isotopic data, provides a powerful tool for classifying the sources of groundwater and identifying the significant factors governing the groundwater quality. The derived knowledge generated by this study constitutes a conceptual framework for investigating groundwater characteristics. This is a prerequisite for developing a sound management plan, which is a requirement for ensuring a sustainable exploitation of the deep aquifer water resource in the coastal area of Tanzania.     

The hydrogeology and hydrogeochemistry of the Barwon Downs Graben aquifer, southwestern Victoria, Australia

The Barwon Downs Graben lies on the northern flanks of the Otway Ranges and is situated approximately 70 km southwest of Geelong, Victoria, Australia. The major lower Tertiary Barwon Downs Graben aquifer comprises highly permeable sands and gravels interbedded with clays and silts of the hydraulically interconnected Pebble Point, Dilwyn and Mepunga Formations. Groundwater flows east into the Barwon Downs Graben from the Barongarook High, and yields ¹⁴C ages up to ～20 ka implying that recharge rates are low and, consequently, that the resource could be impacted by overabstraction. The presence of three different lithological units has led to the development of localized flow systems that has resulted in a lack of regular spatial variations in groundwater chemistry. Stable isotopic data suggests that groundwater was recharged under similar climatic conditions as of today. The major ion chemistry of the freshest groundwater is dominated by Na and HCO₃ while higher TDS groundwater, from the confining Narrawaturk Marl, is dominated by Na and Cl. Cl/Br ratios are close to rainfall suggesting that halite dissolution is not the principle source of salts. An excess of Na relative to Cl in fresher groundwater suggests that feldspar dissolution has occurred, however, water–rock interaction is limited. The concentrations of Ca, Mg, and SO₄ are controlled by silicate dissolution and ion-exchange reactions with clays.     

The origin of fluoride in the granitic aquifer of Porto Alegre, Southern Brazil

The Porto Alegre region, Southern Brazil, comprises a fractured aquifer system constituted by pre-Cambrian granitic and gneissic rocks, and a porous aquifer system formed by Cenozoic muddy–sandy to sandy sediments. A model is presented for the origin of the fluoride in the groundwater of the fractured aquifer system, based on ionic interrelations, a statistical analysis of physicochemical parameters and geochemical modeling. The fluoride is present at levels of up to 6.13 mg/L in groundwater and it arises due to the dissolution of secondary fluorite filling fractures in the granitic and gneissic rocks. The dissolution of fluorite occurs at the same time as calcite and dolomite solubilization. The statistical analysis identified three chemically distinct groups (named 1, 2 and 3) and two subgroups (1A and 1B) of groundwater in the fractured aquifer. The most significant differences between these groups are the different concentration ranges of fluoride, calcium, bicarbonate, magnesium, total dissolved solids and chloride and pH values, as well as the correlations between them. The compositional evolution of each groundwater group is governed mainly by how much high-salinity groundwater from the porous aquifer system is mixed with them and the different thermodynamic equilibrium conditions of calcite, dolomite and fluorite.     

Conceptual model of a coastal aquifer system in northern Greece and assessment of saline vulnerability due to seawater intrusion conditions

This paper refers to the development of a conceptual model for the management of a coastal aquifer in northern Greece. The research presents the interpretation and analysis of the quantitative (groundwater level recordings and design of piezometric maps) regime and the formation of the upcone within the area of investigation. Additionally it provides the elaboration of the results of chemical analyses of groundwater samples (physicochemical parameters, major chemical constituents and heavy metals and trace elements) of the area which were taken in three successive irrigation periods (July–August 2003, July–August 2004 and July 2005), in order to identify areas of aquifer vulnerability. The study identifies the areas where ion exchange phenomena occur, as well as the parts of the aquifer where the qualitative degradation of the aquifer system is enhanced. The paper, finally, assesses the lack of any scientific groundwater resources management of the area by the local water authorities, as well as the current practices of the existing pumping conditions scheme as applied by groundwater users.An erratum to this article can be found at     

Hydrochemistry and isotope geochemistry as tools for groundwater hydrodynamic investigation in multilayer aquifers: a case study from Lomellina, Po plain, South-Western Lombardy, Italy

A multicriteria approach in studying hydrodynamics of a multilayer aquifer system has been used in the Lomellina region (Northern Italy). It involves the reconstruction of the hydrogeological framework coupled to the definition of the hydrochemical and isotopic features of the aquifers. A shallow phreatic aquifer, reaching depths of about 60–80 m from the surface, and deeper aquifers containing confined groundwater, were distinguished. Groundwater generally shows mineralisation decreasing with depth; dissolved ions depict calcium-bicarbonate hydrochemical facies and stable isotopes define the recharge mechanisms, the origin of groundwater, and the hydraulic confinement of deep aquifers. The phreatic aquifer is fed by local infiltration and by streams and irrigation channels. Tritium and Carbon-14 groundwater dating indicate long residence times (on the order of thousands of years) for confined aquifers. The confined aquifers show essentially passive hydrodynamic conditions and maintain a higher piezometric level than the phreatic aquifer. This inhibits the possibility of recent water penetrating far below the surface. The hydrogeological setting of the Lomellina region displays features which are common to other sectors of the Po plain. As a consequence, the results of this study, although conducted on a restricted area, are highly illustrative of groundwater hydrodynamics in large sedimentary aquifers.     

Modeling the impact of groundwater depletion on the hydrochemical characteristic of groundwater within Mullusi carbonate aquifer-west Iraq

The study of groundwater impact on the hydrochemical characteristic of groundwater within Mullusi aquifer, west Iraq was conducted using the chemical analysis results in 14 production wells and groundwater levels observation in 17 water wells. The interpretation of hydrochemical phenomena related to ions sources was determined based on spatial analysis maps of various hydrochemical ratios using ArcGis software. The study also determined the relation of groundwater velocity and static water levels with the hydrochemical ratios using statistical application of Curve expert v1.3 program. The variations of ion concentration were examined using the statistical significant differences for chemical constituents of water within Mullusi aquifer. The impact of dewatering due to high exploitation was explained by increasing the magnesium and chloride concentrations and lowering static water levels. Magnesium and chloride concentration may reach their maximum limits for drinking at a groundwater level of 485 m asl. Accordingly, any decline in the water level of Mullusi aquifer that occurs from 4.5 to 30.5 m may cause deterioration in groundwater quality. This study modeled the effect of groundwater depletion on the groundwater quality in a theoretical equations approach.     

Large-scale aquifer sensitivity model

A 480-square-mile region within Will County, in northeastern Illinois, was used as a test region for the development of a methodology to map the sensitivity of aquifers to contamination. An aquifer sensitivity model was developed using a geographic information system (GIS) to overlay and combine several data layers. The components used for our model are: (1) depth to sand and gravel or bedrock, (2) thickness of the uppermost sand and gravel aquifer, (3) glacial drift thickness, and (4) bedrock geology. The model is an improvement over many previous aquifer sensitivity models because it combines specific information on depth to the uppermost aquifer with information on the thickness of the uppermost sand and gravel aquifer. This county-wide model results in an aquifer sensitivity map that can be a useful tool for making land-use planning decisions regarding aquifer protection and management of groundwater resources.     

A regional-scale groundwater flow model for the Leon-Chinandega aquifer,Nicaragua

Groundwater flow in the Leon-Chinandega aquifer was simulated using transient and steady-state numerical models. This unconfined aquifer is located in an agricultural plain in northwest Nicaragua. Previous studies were restricted to determining groundwater availability for irrigation, overlooking the impacts of groundwater development. A sub-basin was selected to study the groundwater flow system and the effects of groundwater development using a numerical groundwater flow model (Visual MODFLOW). Hydrological parameters obtained from pumping tests were related to each hydrostratigraphic unit to assign the distribution of parameter values within each model layer. River discharge measurements were crucial for constraining recharge estimates and reducing the non-uniqueness of the model calibration. Steady-state models have limited usefulness because of the major variation of recharge and agricultural pumping during the wet and dry seasons. Model results indicate that pumping induces a decrease in base flow, depleting river discharge. This becomes critical during dry periods, when irrigation is highest. Transient modeling indicates that the response time of the aquifer is about one hydrologic year, which allows the development of management strategies within short time horizons. Considering further development of irrigated agriculture in the area, the numerical model can be a powerful tool for water resources management.     

Hydrochemical changes in a small tropical island’s aquifer: Manukan Island, Sabah, Malaysia

Small islands groundwater are often exposed to heavy pumpings as a result of high demand for freshwater consumption. Intensive exploitation of groundwater from Manukan Island’s aquifer has disturbed the natural equilibrium between fresh and saline water, and has resulted increase the groundwater salinity and leap to the hydrochemical complexities of freshwater–seawater contact. An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes and saturation indices. It was observed that the mixing between freshwater–seawater created diversity in geochemical processes of the Manukan Island’s aquifer and altered the freshwater and seawater mixture away from the theoretical composition line. This explained the most visible processes taking place during the displacement.     

Calculation of groundwater head distribution with a close barrier during excavation dewatering in confined aquifer

When pumping is conducted in confined aquifer inside excavation pit(waterproof curtain),the direction of the groundwater seepage outside the excavation changes from horizontal to vertical owing to the existence of the curtain barrier.There is no analytical calculation method for the groundwater head distribution induced by dewatering inside excavation.This paper first analyses the mechanism of the blocking effects from a close barrier in confined aquifer.Then,a simple equation based on analytical solution is proposed to calculate groundwater heads inside and outside of the excavation pit with waterproof curtain(hereafter refer to close barrier)in a confined aquifer.The distribution of groundwater head is derived according to two conditions:(i)pumping with a constant water head,and(ii)pumping with a constant flow rate.The proposed calculation equation is verified by both numerical simulation and experimental results.The comparisons demonstrate that the proposed model can be applied in engineering practice of excavation.     

Hydrogeological characterization of aquifer in palla flood plain of Delhi using integrated approach

The Yamuna flood plains spread across the northern part of Indian subcontinent is home to millions of people. The ever-growing population in these plains make it difficult to sustain the demand of freshwater resources. However, the productive aquifers of flood plains could provide solution for these issues. In this context, it is necessary to understand the aquifer characteristics. Thus, the paper attempts to characterize the aquifer in Palla area of the flood plain using integrated approach. Besides, grain size analysis and site-litholog study, the nature of aquifer material was also ascertained from bulk mineralogy of the sediments using X-Ray Diffraction. The aquifer parameters were estimated with help of long duration pumping test data. Moreover, the effect of pumping on salinity variation and hydrochemical facies evolution was also examined. The sand dominant, unconfined aquifer was estimated to have horizontal hydraulic conductivity in the range of 25 m/day and vertical hydraulic conductivity of 6–7 m /day. While the specific yield of the aquifer was estimated in the range of 0.07–0.08. It is observed that under conducive active flood plain environment, the given sand mineralogy at the site does not allow salinity increase in groundwater even after more than a decade of groundwater pumping. In fact, over years, hydrochemical facies have evolved towards Bicarbonate type. These things put together make the active flood plain aquifer a sustainable groundwater resource.     

Isotopic and hydrochemical studies of groundwater flow and salinity in the Southern Upper Rhine Graben

In order to determine the origin and the propagation mechanisms of highly concentrated chloride brines within the Quaternary aquifer system in the southern part of the Upper Rhine Graben, a combined isotope (H, O, C) and hydrochemical analysis was carried out. Groundwater recharge in this area is a complex system, consisting of local precipitation, river bank filtration, lateral flow from the Graben borders and, to a minor extent, an old Pleistocene component. In some areas, groundwater consists of up to 90% of recent bank filtrate, reaching depths down to at least 100 m. The isotopic and hydrochemical results show, that the elevated chloride concentrations in the Quaternary aquifer mainly result from leaky settling basins charged by the French potash mines until the mid 1970s. Input of natural brines coming from tertiary salt diapirs is of only minor importance. While infiltrating, the anthropogenic brines were strongly diluted by local river bank filtrate of the Rhine. Nevertheless, maximum chloride concentrations nowadays still reach some 10,000 mg/l at the base of the aquifer at a depth of more than 100 m below surface. The main volume of the brines is stored in the less permeable lower part of the quaternary sediments (Breisgau-Formation) whereas only a minor part is transported northwards with the rapid convective groundwater flow. Brines undergoing only dilution preserve their hydrochemical characteristics (NaCl-type). In contrast, brines recirculated from the Breisgau-Formation show a northwards increasing alteration through ion exchange processes. Potassium and sodium may be fixed in the fine grained aquifer material while calcium is set free into the groundwater. After a flow distance of about 12 km, complex hydraulic interactions between groundwater and surface waters lead to the rise of strongly diluted and hydrochemically altered brines with chloride contents up to maximum 700 mg/l. The presented case study is an example for a detailed analysis of a multi-component groundwater mixing system using combined isotope and hydrochemical methods. Furthermore, cation exchange is shown as a major process affecting the hydrochemical evolution of the young groundwater in the southern Upper Rhine Graben which is locally strongly polluted by chloride as a consequence of former potash mining.