An integrated approach to assess the quality of groundwater in a coastal aquifer of Andhra Pradesh, India

The Narava basin in Visakhapatnam district situated on the east coast is a productive agricultural area, and is also one of the fastest growing urban areas in India. The agricultural and urban-industrialization activities have a lot of impact on this coastal aquifer water quality. The hydrochemistry of the groundwater was analyzed in the basin area with reference to drinking and agricultural purposes. The area is underlain by Precambrian rocks like khondalites, charnockites and migmatites. The water samples were collected from shallow wells for the year 2008. Physical and chemical parameters of groundwater such as pH, total alkalinity (TA), electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃ ^?, Cl^?, SO₄ ^2?, NO₃ ^?, F^? were determined. The analytical results revealed that the most of the groundwater found to be in polluted category. Geographical information system (GIS) was utilized to generate different spatial distribution maps of various chemical constituents in the study area. The analytical data were used to compute certain parameters such as salinity hazard, percent sodium (Na%), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), permeability index (PI), Kelley??s ratio (KR) and corrosivity ratio (CR) to determine the quality of water for agricultural purposes. The abundance of the major ions in the basin area was found to be in the following sequence: Na⁺?>?Ca²⁺?>?Mg²⁺?>?K⁺:Cl^??>?HCO₃ ^??>?SO₄ ^2??>?NO₃ ^??>?F^?. According to Gibbs?? diagram most of the samples fall under rock dominance. As per Wilcox and USSL classification most of the groundwater samples are suitable for irrigation except few samples which are unsuitable due to the presence of high salinity and high sodium hazard. From the obtained data, it can be concluded that the water quality profile was good and useful for normal irrigation agriculture.     

Assessment of hydrochemistry and groundwater quality in the coastal area of South Chennai,India

An attempt has been made to evaluate the water quality in the fast-growing coastal area of South Chennai. Groundwater samples were collected from selected locations and analyzed for major physico-chemical parameters. Experimental results show that the water has alkaline with pH varying from 7.2 to 8.2. Concentrations of Na and Cl were positively correlated with EC and elevated levels of these parameters near the coastal region, especially in the northern end of the study area, indicating the influence of seawater intrusion. Piper diagram identified Na–Cl as the dominant type of water in most of the samples. The presence of Ca–Cl facies in the groundwater suggests the possible ion exchange (Na with Ca) reaction in the aquifer. Molar ratios of Cl/HCO₃ and Mg/Ca showed a higher value (>1) in many samples, which confirmed the influence of seawater intrusion on water quality. The Water Quality Index (WQI) of the study area ranged between 8 and 116, the highest recorded being at Thiruvanmiyur and the lowest at Muttukkadu. However, total hardness values show that 64% of the samples were hard or very hard in nature. The results of SAR, Na%, and PI show that majority of the samples are suitable for irrigation purposes. A comparison of spatial distribution maps of water quality parameters with those of WQI shows that groundwater quality has highly deteriorated in the Thiruvanmiyur region, located on the northeast part of the study area. Good-quality water is found at the southeast part of the study area, namely, Muttukkadu. This study indicates that urbanization and seawater intrusion have heavily affected the groundwater quality of South Chennai coastal area.     

Geologic factors controlling groundwater chemistry in the coastal aquifer system of Douala/Cameroon: implication for groundwater system functioning

Douala city, located in the littoral province of Cameroon, receives abundant rainfall quantities due to its geographical position in the Gulf of Guinea and bears considerable surface water and groundwater resources. Due to socioeconomic development and rapid demographic growth in the city and its consequences of unplanned urbanization and improper sanitation system, these water resources are poorly protected and managed. Streams in the Wouri watershed receive large amounts of wastewater discharge, and hundreds of boreholes have been drilled into the aquifer system without any management plan. A detailed hydrodynamic and hydrogeochemistry study in Douala town and its environs was conducted to get a better insight into the groundwater system functioning in order to provide information for the sustainable management and protection of the groundwater resource. Two field campaigns were carried out with 187 samples collected and analyzed for major ions, stable isotopes (¹⁸O, ²H), and tritium ³H. The results of the sampling have shown that the weathering of silicate minerals is the dominant geochemical process affecting groundwater chemistry in this system. However, acid rainfall in the humid climate has also caused carbonate mineral dissolution, amorphous silica deposition, and ion exchange reactions to occur in aquifers in the region. The various water types identified were categorized into four major clusters C1 to C4, based on the major ion composition and the local hydrogeological conditions. Environmental isotope data reveal that modern-to-submodern waters occur in the phreatic Quaternary/Mio-Pliocene and Oligocene/Upper Eocene aquifers, respectively. These results corroborate with the conceptual model built where modern groundwater types indicated silicate mineral weathering and calcite dissolution (C1 and C2), whereas submodern groundwater mostly showed silica deposition, ion exchange, and, to a lesser extent, carbonate mineral dissolution (C3 and C4). This improved understanding of the aquifer system functioning is essential to provide a reasonable basis for effective control measures and sustainable water management.     

Degradation of groundwater quality in coastal aquifer of Sabratah area,NW Libya

Overextraction of groundwater is widely occurring along the coast where good quality groundwater is at risk, due to urbanization, tourist development and intensive agriculture. The Sabratah area at the northern central part of Jifarah Plain, Northwest Libya, is a typical area where the contamination of the aquifer in the form of saltwater intrusion, gypsum/anhydrite dissolution and high nitrate concentrations is very developed. Fifty groundwater samples were collected from the study area and analysed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters electrical conductivity, sodium, potassium, magnesium, chloride and sulphate which can be attributed to seawater intrusion. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 30 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high nitrate concentration towards the south of the region. Seawater intrusion and deep salt water upconing result in general high SO₄ ^2? concentrations in groundwater near the shoreline, where localized SO₄ ^2? anomalies are also due to the dissolution of sebkha deposits for few wells in the nearby sebkhas. Upstream, the increase in SO₄ ^2? concentrations in the south is ascribed to the dissolution of gypsum at depth in the upper aquifer.     

Environmental magnetic and geochemical characteristics of Chennai coastal sediments,Bay of Bengal,India

In this study, environmental magnetic, heavy metal and statistical analyses were conducted on 21 surface sediments collected from Chennai coast, India, to examine the feasibility of heavy metal pollution using magnetic susceptibility. The Chennai coastal sediment samples are dominated by ferrimagnetic minerals corresponding to magnetite-like minerals. The percentage of frequency dependent magnetic susceptibility reflects the presence of super-paramagnetic/single domain magnetic minerals in Chennai harbour, Cooum and Adayar rivers sediments. High pollution load index in sample E1, E2, CH7, C11, C12 and A16 is mainly due to anthropogenic activities such as, harbour activities, Cooum and Adayar rivers input and industrial effluent. Factor analysis shows that the magnetic concentration dependent parameters (χ, χ _ARM and SIRM) covary with the heavy metal concentrations, suggesting that the input of magnetic minerals and heavy metals in Chennai coastal sediments are derived from the same anthropogenic sources. Strong correlation obtained between pollution load index (PLI) and concentration dependent parameters (χ, χ _ARM and SIRM) for the polluted samples with magnetic susceptibility excess of 50×10^− 8 m³kg^− 1. Significant correlations between heavy metals and magnetic susceptibility point out the potential of magnetic screening/monitoring for simple and rapid proxy indicator of heavy metal pollution in marine sediments.     

Hydrologic factors controlling groundwater salinity in northwestern coastal zone,Egypt

The aim of this article is to assess the main factors influencing salinity of groundwater in the coastal area between El Dabaa and Sidi Barani, Egypt. The types and ages of the main aquifers in this area are the fractured limestone of Middle Miocene, the calcareous sandstone of Pliocene and the Oolitic Limestone of Pleistocene age. The aquifers in the area are recharged by seasonal rainfall of the order of 150 mm/year. The relationship of groundwater salinity against the absolute water level, the well drilling depth, and the ability of aquifer to recharge has been discussed in the present work. The ability of aquifer to locally recharge by direct rainfall is a measure of the vertical permeability due to lithological and structural factors that control groundwater salinity in the investigated aquifers. On the other hand, the fracturing system as well as the attitude of the surface water divide has a prime role in changing both the mode of occurrence and the salinity of groundwater in the area. Directly to the west of Matrouh, where the coastal plain is the narrowest, and east of Barrani, where the coastal plain is the widest, are good examples of this concept, where the water salinity attains its maximum and minimum limits respectively. Accordingly, well drilling in the Miocene aquifer, in the area between El Negila and Barrani to get groundwater of salinities less than 5000 mg/l is recommended in this area, at flow rate less than 10 m³/hr/well. In other words, one can expect that the brackish water is probably found where the surface water divide is far from the shore line, where the Wadi fill deposits dominate (Quaternary aquifer), acting as a possible water salinity by direct rainfall and runoff.     

Sustainability analysis of groundwater resources in a coastal aquifer, Alabama

Fort Morgan Peninsula is an attached portion of a dynamic barrier complex in the northern Gulf of Mexico and is a large tourist area that brings in a significant amount of revenue for Alabama. Many of the hotels and tourist attractions depend on the groundwater as their water supply. The over-withdrawal of groundwater and saltwater intrustion will have a negative impact on the ecology, tourism and economy if groundwater resources are not properly monitored and managed. In this study a calibrated groundwater flow model was used to analyze the sustainability of groundwater resources at Fort Morgan Peninsula. Detailed flow budgets were prepared to check the various components of inflow and outflow under different water use and climatic conditions. The results indicated the locations where groundwater was over-pumped and subjected to saltwater intrusion, or will be subjected to saltwater intrusion under a range of projected water use and climatic conditions.     

Assessment of groundwater salinity using GIS and multivariate statistics in a coastal Mediterranean aquifer

The integration of the statistical approaches and GIS tools with the hydrogeological and geological contexts allowed the assessment of the processes that cause groundwater quality deterioration in the great important deltaic aquifer in the northeastern Tunisia (Medjerda Lower Valley Aquifer). The spatial variation of the groundwater parameters and the molar ratio (Cl^?/Br^?) were also used to determine the possible impacts from seawater intrusion and from the septic tank leachate. Sixty shallow groundwater samples were collected in 2014 and analyzed for major and trace ions over an area of about 1090 km² to determine the suitability for drinking or agricultural purposes. The total dissolved solids (TDS) content ranges from 1005 to 19,254 mgl^?1 with a mean value of 3477.18 mgl^?1. The chemistry is dominated by the sodium–chloride waters (55%). Mapping of TDS, Cl^?, Na⁺, SO₄^2? and NO₃^? using kriging method shows a clear increase in salinity toward the coastline accompanied by Na⁺ and Cl^? increase which may be related to seawater intrusion and halite dissolution. Locally, higher nitrate concentration is related to the agricultural activities inducing contribution of chemical fertilizers and irrigation with treated wastewater. The saturation indices indicate that all carbonate minerals tend to reach saturation equilibrium confirming water–rock interactions, while evaporitic minerals are still in sub-saturation state and may increase the salinity of the groundwater. The principal component analysis proves the occurrence of groundwater contamination principally by seawater intrusion in the factor I (74.15%) and secondary by an anthropogenic source in the factor II (10.35%).     

Identification of seawater intrusion signatures through geochemical evolution of groundwater: a case study based on coastal region of the Mahanadi delta,Bay of Bengal,India

Natural Hazards - The study dealt with seawater intrusion process in a coastal aquifer system in the Mahanadi river delta region in the east coast of India along the Bay of Bengal. The aquifers of...     

Processes affecting groundwater temperature patterns in a coastal aquifer

The temperature depth profiles of six wells in the Motril-Salobren～a aquifer were used as a basis for a comparative analysis involving various parameters to determine their relations and factors influencing the different trends. There is a clear influence of ambient temperature on all the profiles, with a lag time of two to five months. Nevertheless, there are clear differences in the temperature depth profile patterns that can be accounted for by other factors. First, there is a greater influence of localized recharge; Guadalfeo River as opposed to diffuse recharge; irrigation return flow and rainfall. Three of the wells located near the riverbed of the Guadalfeo River have extremely variable temperature-depth profiles and show clear river influence. In springtime, during the highest flood stages of the river due to cold melt water from the Sierra Nevada, the groundwater falls in temperature. During secondary peaks in river flow rates during the autumn due to rainfall, the warm water increases groundwater temperature. The effect of the river recharge decreases with distance from the course since there is less mixing with water from the Guadalfeo River. In addition, there are two temperature-depth profiles in which temperature variations remain shallow and follow a pattern that cannot be attributed to the influence of either of the above two parameters. Among these two cases, the most influential factor is the groundwater flow pattern typical of a discharge zone, characterized by vertical-flow components.     

Geoenvironmental appraisal of groundwater quality in Bengal alluvial tract,India: a geochemical and statistical approach

Groundwater is an essential natural resource which has enormous use throughout the world, but with the enhanced population pressure, its quality and quantity gets affected. Consequently, assessment and categorization of groundwater quality is necessary and the availability of safe water for utilization is to be ensured. The present study was based on groundwater samples, collected over 5,324 km² from the alluvial tract of Bengal plain, India. Ten geochemical parameters viz. arsenic, pH, total dissolved solids, electrical conductivity, iron, total hardness as calcium carbonate, sulphate, nitrite and depth were analysed, and multivariate statistical analyses were performed on the data set. Factor analysis depicted four factors, which explained 66.57 % of total variability of data. Factor 1 represented high positive loadings on total dissolved solids and electrical conductivity. Factor 2 was associated with depth, arsenic and iron and indicated process of reduction in groundwater. Over extraction of groundwater showed probable relationship with arsenic concentration in groundwater. Parameters of Factor 3 and 4 had been related with agricultural activities and local geological conditions. Further, four clusters observed from hierarchical cluster analysis, assisted in grouping groundwater geochemistry of the region. The results coupled with GIS facilitated in categorizing and mapping the groundwater quality.     

Assessment of groundwater quality in and around Vedaraniyam,South India

Groundwater from 47 wells were analyzed on the basis of hydrochemical parameters like pH, electric conductivity, total dissolved solids, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, CO₃ ^2?, HCO₃ ^?, NO₃ ^?, PO₄ ^3? and F^? in the Cauvery delta of Vedaraniyam coast. Further, water quality index (WQI), sodium percentage (Na %), sodium absorption ratio, residual sodium carbonate, permeability index and Kelley’s ratio were evaluated to understand the suitability of water for drinking and irrigation purposes. The result shows significant difference in the quality of water along the coastal stretch. The order of dominance of major ions is as follows: Na⁺ ≥ Mg²⁺ ≥ Ca²⁺ ≥ K⁺ and Cl^? ≥ HCO₃ ^? ≥ CO₃ ^2? ≥ PO₄ ^3? ≥ F^?. Na/Cl, Cl/HCO₃ ratio and Revelle index confirmed that 60–70 % of the samples were affected by saline water intrusion. WQI showed that 36 % of the samples were good for drinking and the remaining were poor and unsuitable for drinking purpose. The degradation of groundwater quality was found to be mainly due to over-exploitation, brackish aquaculture practice, fertilizer input from agriculture and also due to domestic sewage.     

Delineation of groundwater salinization in a coastal aquifer, Bousheher, South of Iran

The geochemical processes controlling chemical composition of groundwater are studied using hydrochemical and isotopic data in Abdan-Dayer coastal plain, south of Iran. The salinity of groundwater in the coastal plain ranges from 1,000, a fresh end-member, to more than 50,000 μS cm^?1, a saline end-member. Groundwater salinity increases from the recharge area toward areas with a shallow water table close to the Persian Gulf coast due to direct evaporation and sea water intrusion as confirmed by mixing binary diagrams, stable isotope content, and Br^?/Cl^? ratio. Groundwater flow pattern in the study area has been modified due to over-pumping of groundwater in recent years which resulted in further saline water migration toward fresh water and their mixing. The maximum mixing ratio is estimated about 15% in different parts of the study area according to chloride concentration.     

Study of subsurface geology in locating arsenic-free groundwater in Bengal delta,West Bengal,India

Over a large area of the Bengal delta in West Bengal, India, arsenic distribution patterns in groundwater were studied. One hundred and ten boreholes at different target locations were made, subsurface sediments were logged and analysed, and arsenic values in sediments vis-à-vis groundwater were compared. The study elucidates the subsurface geology of the western part of Bengal delta and characterises the sediments that were intersected in different boreholes with contrasting values of arsenic in groundwater. It reveals an existence of multiple aquifers stacked over each other. Depending on the color and nature of aquifer-sands and their overlying clay beds six aquifer types (Type-1 to Type-6) are classified and described. Sediment-arsenic for all the varieties of aquifer sands are near similar but the groundwater-arsenic of these six aquifers varies widely. Type-2 and Type-5 aquifers host arsenic-contaminated groundwater whereas the other four aquifers are arsenic-free. Type-2 and Type-5 aquifers are capped by a grey to dark grey soft organic matter-rich clay unit which makes these aquifers semi-confined to leaky-confined. These contribute in releasing arsenic from the sediments. The results of this study are employed in a proposed georemedial measure against this hazardous toxic element.     

Geochemistry of groundwater,Burdwan District,West Bengal,India

Hydrogeochemical investigations are carried out in the different blocks of Burdwan district, West Bengal, India in order to assess its suitability for drinking as well as irrigation water purpose. Altogether 49 representative groundwater samples are collected from bore wells and the water chemistry of various ions viz. Ca²⁺, Mg²⁺, Na⁺, K⁺, CO₃²⁻, HCO₃⁻, Cl⁻, SO₄²⁻ and NO₃⁻ are carried out. The chemical relationships in Piper and Gibbs diagram suggest that the groundwater mainly belongs to alkali type and Cl⁻ group and are controlled by rock dominance. A comparison of groundwater quality in relation to drinking water quality standards proves that most of the water samples are suitable for drinking water purpose whereas groundwater in some areas of the district has high salinity and high sodium adsorption ratio (SAR), indicating unsuitability for irrigation water and needs adequate drainage.     

A study on the hydrogeology and hydrogeochemistry of groundwater from different depths in a coastal aquifer: Annamalai Nagar,Tamilnadu, India

Chemical characterization of groundwater is essential to bring out its nature and utility. Samples from shallow and deep ground water of the same location were collected and studied for their geochemical characteristics following standard procedures (APHA 1998). Sediment samples from different depths were collected and analysed for minerals using FTIR and SEM. Resisitivity logging was carried out in the bore well to understand the variations in depth to fresh water potential. The shallow ground water is dominated by Na–Cl–HCO₃–SO₄ and deeper groundwater by Na–HCO₃–SO₄–Cl types. It is observed that there is a significant ionic variation with depth. The ionic strength of the deeper samples is lesser than in the shallower samples. Wide pH variations in the shallow water samples are due to ion exchange process. Thermodynamic stability plot was used to identify the state of stability. It is inferred that there is no major significant difference in the thermodynamic state of stability in the shallow and the deeper aquifers as the aquifer matrix for the shallow and deeper aquifers are almost similar. Saturation index of Gibbsite, Kaolinite, Calcite, Dolomite and anhydrite, were studied for shallow and deep aquifers, to identify the difference in hydro chemical signatures. The Si/Al ratios of shallow samples are less when compared with the deeper samples. Leaching of secondary salts was the chief mechanism controlling the ground water chemistry of the region.     

Assessment of groundwater quality in the flood plains of upper Palar River, India

Groundwater is generally presumed to be good for human consumption and is used as a main source of drinking water. Although there are numerous reasons for groundwater pollution, anthropogenic sources are consid-ered as the prime ones. In this study, twenty-two groundwater samples were collected from the flood plains of upper Palar River during the pre- and post-monsoon seasons to assess the extent of pollution and effects on human health. Physico-chemical characteristics of groundwater were analyzed and compared with those of drinking water standards recommended by the World Health Organization (WHO) and the Bureau of Indian Standards (BIS). The Piper’s tri-linear diagram shows the nature of alkali earth with the high contents of alkalies and prevailing sulphate in the pre-sent samples. The univariate statistics and correlation analysis were performed to find out the relationships between the variables. The tannery effluents, solid wastes and sewage were suspected to be the predominant sources of pollu-tion in the area.