Quality assessment of groundwater from the south-eastern Arabian Peninsula

Assessment of groundwater quality plays a significant role in the utilization of the scarce water resources globally and especially in arid regions. The increasing abstraction together with man-made contamination and seawater intrusion have strongly affected groundwater quality in the Arabia Peninsula, exemplified by the investigation given here from the United Arab Emirates, where the groundwater is seldom reviewed and assessed. In the aim of assessing current groundwater quality, we here present a comparison of chemical data linked to aquifers types. The results reveal that most of the investigated groundwater is not suitable for drinking, household, and agricultural purposes following the WHO permissible limits. Aquifer composition and climate have vital control on the water quality, with the carbonate aquifers contain the least potable water compared to the ophiolites and Quaternary clastics. Seawater intrusion along coastal regions has deteriorated the water quality and the phenomenon may become more intensive with future warming climate and rising sea level.     

Can groundwater vulnerability models assess seawater intrusion?

This study examines the uncertainty associated with two commonly used GIS-based groundwater vulnerability models, DRASTIC and EPIK, in assessing seawater intrusion, a growing threat along coastal urban areas due to overexploitation of groundwater resources. For this purpose, concentrations of Total Dissolved Solids (TDS) in groundwater samples at three pilot areas along the Eastern Mediterranean were compared with mapped vulnerability predictions obtained through DRASTIC and EPIK. While field measurements demonstrated high levels of groundwater salinity depending on the density of urbanization, both vulnerability assessment methods exhibited a limited ability in capturing saltwater intrusion dynamics. In the three pilot areas, DRASTIC was only able to predict correctly between 8.3 and 55.6% of the salinity-based water quality ranges, while EPIK's predictions ranged between 11.7 and 77.8%. This emphasizing that conventional vulnerability models perform poorly when anthropogenic impacts induce lateral flow processes such as seawater intrusion caused primarily by vertical groundwater extraction.     

Estimation of spatial distrubition of groundwater level and risky areas of seawater intrusion on the coastal region in Çarşamba Plain,Turkey, using different interpolation methods

Groundwater level plays a significant role in coastal plains. Heavy pumping and excessive use of near-coast groundwater can increase the intrusion of seawater into the aquifers. In the present study, groundwater levels were measured at 59 groundwater wells at different times during pre- and post-irrigation seasons (April and September of the year 2012) in Çar?amba Plain, Turkey. To select the best method, two deterministic interpolation methods (inverse distance weighing (IDW) with the weights of 1, 2, and 3 and radial basis function (RBF) with spline with tension (SPT) and completely regularized spline (CRS)) and two stochastic methods (ordinary kriging (OK) with spherical, exponential, and Gaussian variograms) and cokriging (COK)) were compared and then the best interpolation method was used to evaluate the spatial distribution of groundwater levels in different seasons and seasonal changes. A total of nine different techniques were tested. Also, risky areas of seawater intrusion in coastal area were determined using the best methods for two periods. The performance of these interpolation methods is evaluated by using a validation test method. Statistical indices of correlation (R ²), mean absolute error (MAE), and root-mean-square error (RMSE) were used to select and validate the best methods. Comparisons between predicted and observed values indicated RBF as the optimal method for groundwater level estimation in April and September. When the best method RBF and the worst method IDW were compared, significant differences were observed in the spatial distribution of groundwater. Results of the study also revealed that excessive groundwater withdrawals during the post-irrigation season dropped the groundwater levels up to 2.0 m in some sections. With regard to seawater intrusion, 9,103 ha of land area was determined to be highly risky and risky.     

Water quality decline in coastal aquifers under anthropic pressure: the case of a suburban area of Dakar (Senegal)

In recent years, the unregulated increase of the population in coastal areas of developing countries has become source of concern for both water supply and quality control. In the region of Dakar (Senegal), approximately 80% of water resources come from groundwater reservoirs, which are increasingly affected by anthropogenic pressures. The identification of the main sources of pollution, and thus the aquifer vulnerability, is essential to provide a sound basis for the implementation of long-term geochemically based water management plans in this sub-Saharan area. With this aim, a hydrochemical and isotopic survey on 26 wells was performed in the so-called Peninsula of Cap-Vert. Results show that seawater intrusion represents the main process affecting groundwater chemical characteristics. Nitrates often exceed the World Health Organization drinking water limits: stable isotopes of dissolved nitrate ( $\updelta ^{15}$ N and $\updelta ^{18}$ O) indicate urban sewage and fertilizers as a major source of contamination. Results depict a complex situation in which groundwater is affected by direct and indirect infiltration of effluents, mixing with seawater and freshening processes from below. Besides the relevance of the investigation at a regional level, it represents a basis for decision-making processes in an integrated water resources management and in the planning of similar monitoring strategies for other urban coastal regions.     

Impacts of seawater intrusion on soil salinity and alkalinity in Bafra Plain, Turkey

This study was carried out to investigate possible seawater intrusion into groundwater along the coastal lines of the Bafra Plain and salinity–alkalinity problems over land areas irrigated with water exposed to seawater intrusion were evaluated. For this purpose, 32 groundwater wells were selected over the plain, water samples were taken from these wells between October 2007 and September 2008, and chemical analyses were performed over these samples. Soil samples were taken from the fields irrigated with this water at 32 different locations at the end of the irrigation season in September 2008 from 0–30, 30–60, 60–90, and 90–120 cm soil depths and textures. EC, pH, Na, Ca, Mg, and K analyses were performed over these samples. Excessive seawater intrusion was observed in some parts of the plain and impacts of seawater intrusion decreased with the distance from the coastal line. It was determined that groundwater quality was significantly affected from seawater intrusion. Salinity and especially alkalinity problems were observed in land areas irrigated with this water and alkalinity increased with the rate of intrusion.     

Sea water intrusion studies near Kovaya limestone mine, Saurashtra coast, India

The Kovaya Limestone Mine is situated on the Saurashtra coast of India. Though the mine is dependent on the desalination plant installed in the plant for its domestic and industrial water requirements, there is significant withdrawal of groundwater by the large number of bore wells and open wells, which are present in the agricultural fields lying in and around the leased area of the mine. The heavy withdrawal of groundwater has led to intrusion of seawater. The present work entails study of possible seawater intrusion by chemical analysis of major cations and anions in selected groundwater samples. Very high total dissolved solids in the range of >1,000 mg/l and high chloride in the range of 103 mg/l to 3,899 mg/l have been measured in the groundwater samples. 'Resistivity Imaging Survey' has also been carried out on selected profiles in the study area. The Electrical Resistivity Tomography images indicate very low resistivity zones (~0-3 Omega m) in the bottom portion of the resistivity depth section. These low resistivity zones can be interpreted to be due to seawater intrusion. The resistivity sections on the excavated Pits, where mining is going on, indicate possibilities of seawater intrusion. Hence, protection from seawater intrusion is recommended through restriction of mining up to the safe level.     

Assessment of geochemical processes occurring in groundwaters in the coastal alluvial aquifer

Groundwater samples are collected from 30 observation wells in the study area to analyze the hydrochemical quality for determining the seawater encroachment in the part of Central Godavari Delta, Bay of Bengal, India. In order to establish the baseline hydrochemical conditions and processes determining the groundwater quality, an integrated investigation coupled with multivariate statistical analysis and hydrochemical methods are used to identify and interpret the groundwater chemistry of the aquifer system. The major land use is irrigated agriculture and aquaculture in the study area. The ground waters affected by the seawater intrusion featured high levels of sodium (Na⁺), chloride (Ca⁺), and TDS, which are the simplest common indicators for seawater influence. The elevated levels of NO₃–N at some monitoring wells indicate nitrate pollution of groundwater due to anthropogenic origin such as septic effluents or chemical fertilizers. Besides the major chemical compositions, it was also demonstrated that ionic ratios would be useful to delineate seawater intrusion and they include Na⁺/Ca²⁺, Mg²⁺/Ca²⁺, SO₄ ^2?/Ca²⁺, Na⁺/(Na⁺?+?Cl^?), and Ca^?/sum of anions. This paper demonstrates the variations in hydrochemical quality of groundwater and its evolution processes in two different seasons in the coastal aquifer alluvial settings     

Nitrate occurrence in the groundwater of the Loukkos perimeter

This study assesses the occurrence of nitrate in the groundwater beneath the R'mel area of the Loukkos perimeter (north-west Morocco), which covers an approximate area of 2,560 km2 and is located between the towns of Ksar el Kebir and Larache. It also borders the Atlantic Ocean. Groundwater supplies are the principal source of drinking water in this region and there is no public drinking water network in the rural area. This perimeter has a population of about 500,000 inhabitants of which the rural population represents 60%, many of whom have depended on and used the water from the aquifers for many years. The inhabitants and farmers depend on the groundwater supplies for drinking water, crop irrigation and other uses. The plain provides the ideal conditions for agriculture and the use of chemical fertilisers has been increasing. In this study, 53 water samples were collected from wells and springs. Each well or spring was sampled once or twice during 1998-2000. Nitrate concentrations ranged from extremely low up to 144 mg L(-1). Nitrate concentrations exceeded the maximum contaminant level (MCL) of 50 mg L(-1) in 12 of the 53 groundwater samples (23%), whereas 31 of the 53 samples (58%) had nitrate concentrations of less than 25 mg L(-1).     

Assessment of groundwater vulnerability in the coastal region of Oman using DRASTIC index method in GIS environment

A study was carried out to develop a vulnerability map for Barka region in the North Batina of Oman using DRASTIC vulnerability index method in GIS environment. DRASTIC layers were created using data from published reports and the seven DRASTIC layers were processed by the ArcGIS geographic information system. Finally, DRASTIC maps were created for 1995 and 2004 to understand the long-term changes in the vulnerability index. DRASTIC vulnerability maps were evaluated using groundwater quality data such as chemical and biological parameters. DRASTIC vulnerability maps of 1995 and 2004 indicate that the northern part of Barka is more vulnerable to pollution than southern part and the central part of Barka also shows high relative vulnerability which is mostly related to the high conductivity values. Moreover, the changes in water level due to high abstraction rate of groundwater reflect in the vulnerability maps and low vulnerability area is increased in the southern part during 2004 compared to 1995. Moreover, regional distribution maps of nitrate, chloride and total and fecal coliforms are well correlated with DRASTIC vulnerability maps. In contrast to this, even though DRASTIC method predicted the central part of the study region is highly vulnerable, both chemical and biological parameters show lower concentrations in this region compared to coastal belt, which is mainly due to agricultural and urban development. In Barka, urban development and agricultural activities are very high in coastal region compared to southern and central part of the study area. Hence, this study concluded that DRASTIC method is also applicable in coastal region having ubiquitous contamination sources.     

Groundwater contamination and its effect on health in Turkey

The sources of groundwater pollution in Turkey are identified, and pathways of contaminants to groundwater are first described. Then, the effects of groundwater quality on health in Turkey are evaluated. In general, sources of groundwater contamination fall into two main categories: natural and anthropogenic sources. Important sources of natural groundwater pollution in Turkey include geological formations, seawater intrusion, and geothermal fluid(s). The major sources of anthropogenic groundwater contamination are agricultural activities, mining waste, industrial waste, on-site septic tank systems, and pollution from imperfect well constructions. The analysis results revealed that natural contamination due to salt and gypsum are mostly found in Central and Mediterranean regions and arsenic in Aegean region. Geothermal fluids which contain fluoride poses a danger for skeleton, dental, and bone problems, especially in the areas of Denizli, Isparta, and Ayd?n. Discharges from surface water bodies contaminate groundwater by infiltration. Evidence of such contamination is found in Upper K?z?l?rmak basin, Gediz basin, and Büyük Melen river basin and some drinking water reservoirs in ?stanbul. Additionally, seawater intrusion causes groundwater quality problems in coastal regions, especially in the Aegean coast. Industrial wastes are also polluting surface and groundwater in industrialized regions of Turkey. Deterioration of water quality as a result of fertilizers and pesticides is another major problem especially in the regions of Mediterranean, Aegean, Central Anatolia, and Marmara. Abandoned mercury mines in the western regions of Turkey, especially in ?anakkale, ?zmir, Mu?la, Kütahya, and Bal?kesir, cause serious groundwater quality problems.     

Deterioration of coastal groundwater quality in Island and mainland regions of Ramanathapuram District, Southern India

A study was carried out in the Island and mainland regions of Ramanathapuram District to characterize the physico-chemical characteristics of 87 groundwater samples in Island and 112 groundwater samples in mainland which include pH, EC, TDS, salinity, total alkalinity, calcium hardness, magnesium hardness, total hardness, chloride and fluoride. Heavy inorganic load in majority of the groundwater samples has been estimated due to the salinity, TDS, TH and chloride beyond the threshold level which substantiates the percolation of sea water into the freshwater confined zones. Although the groundwater sources are available in plenty, the scarcity of potable water is most prevalent in this coastal area. The Water Quality Index (WQI) and Langeleir Saturation Index (LSI) have also been calculated to know the potable and corrosive/incrusting nature of the water samples. The statistical tools such as principal component analysis, box plots and correlation matrix have also been used to explain the influence of different physico-chemical parameters with respect to one another among the groundwater samples. The percentage of groundwater samples in mainland was more than that in Island with respect to the acceptable limit of WHO drinking standard, especially in TDS, CH, TH and chloride but the converse is observed in the case of fluoride. About 8 % of the mainland aquifers and 42 % of Island aquifers were identified to have fluoride greater than 1.5 mg/l. The signature of salt-water intrusion is observed from the ratio of Cl/CO ₃ ^2? ?+?HCO₃ and TA/TH. A proper management plan to cater potable water to the immediate needs of the people is to be envisaged.     

Does irrigation with reclaimed water significantly pollute shallow aquifer with nitrate and salinity? An assay in a perurban area in North Tunisia

In Tunisia, reclaimed water is increasingly used for irrigation in order to mitigate water shortage. However, few studies have addressed the effect of such practice on the environment. Thus, we attempted in this paper to assess the impact of irrigation with reclaimed water on the nitrate content and salinity in the Nabeul shallow aquifer on the basis of satellite images and data from 53 sampled wells. Ordinary and indicator kriging were used to map the spatial variability of these groundwater chemical parameters and to locate the areas where water is suitable for drinking and irrigation. The results of this study have shown that reclaimed water is not an influential factor on groundwater contamination by nitrate and salinity. Cropping density is the main factor contributing to nitrate groundwater pollution, whereas salinity pollution is affected by a conjunction of factors such as seawater interaction and lithology. The predictive maps show that nitrate content in the groundwater ranges from 9.2 to 206 mg/L while the electric conductivity ranges from 2.2 to 8.5 dS/m. The high-nitrate concentration areas underlie sites with high annual crop density, whereas salinity decreases gradually moving away from the coastline. The probability maps reveal that almost the entire study area is unsuitable for drinking with regard to nitrate and salinity levels. Appropriate measures, such as the elaboration of codes of good agricultural practices and action programs, should be undertaken in order to prevent and/or remediate the contamination of the Nabeul shallow aquifer.     

Feasibility study of rainwater harvesting system in Sylhet City

In rural areas in Bangladesh, groundwater is the principal source of water supply. This underground water is available in considerable amount in shallow aquifers. It is free from pathogenic microorganisms and hence water-borne diseases. In plain lands, other than hilly areas, water supply to 97% rural population comes from tube-wells, which is regarded to be a phenomenal achievement in preserving public health. Besides, a dependable water supply system all throughout the country is offset by two factors: (a) high salinity in surface plus groundwater in coastal areas; (b) want of suitable groundwater aquifers in hilly areas and the high cost of setting up tube-wells due to deep underground water table and stony layers. However, presence of arsenic in underground water now poses a serious threat to the success once made in water supply by setting up of manually operated tube-wells in the village areas—the achievement is now on the brink of total collapse. In about 61 districts out of 64, presence of arsenic exceeds a quantity of 0.05 mg/1, a permissible limit as per Bangladeshi water quality standard. Harvesting rainwater can be a pragmatic solution to this problem, which is common in many places in Sylhet especially in the hilly areas on the north eastern part of the city. This can be an alternative source of drinking water because of availability of rainwater from March to October. Heavy rain occurs from end of May till mid September, which is commonly known as the rainy season. This paper focuses on the possibility of harvesting rainwater in rural communities and thickly populated urban areas of Sylhet. It also demonstrates the scopes of harvesting rainwater using simple and low-cost technology. With setting up of a carefully planned rainwater storage tank, a family can have all of its drinking water from rain. Planned use of rainwater through rainwater harvesting in the roof catchments may fulfill the entire annual domestic water demand of a family in the rural areas of Bangladesh.     

Design of National Groundwater Quality Monitoring Network in Egypt

In the Nile Valley and Delta the protection of groundwater resources is high priority environmental concern. Many groundwater quality problems are already dispersed and may be widespread and frequent in occurrence. Examples include problems associated with the extensive application of chemical fertilizers in agricultural specially in the new reclaimed areas, leaks in sewers, septic tanks, the aggregate effects of many different points source pollution in urban areas and natural, geologically related water quality problems. A national groundwater quality monitoring has been designed and implemented based on the stepwise procedure. The national groundwater quality monitoring network is used to quantify the quality changes in long run, either caused by pollution activities or by salt water intrusion and to describe the overall current groundwater quality status on a national scale of the main aquifers. The monitoring tools and methodologies developed in this research can be used to assure protection of public health and determine the sustainability of groundwater in various purposes. This national monitoring network plays important roles for decision makers in developing the groundwater resources management plans in different aquifers systems in Egypt.     

Hydrochemical and geoelectrical investigation of the coastal shallow aquifers in El-Omayed area, Egypt

Monitoring and assessment of the coastal aquifers are becoming a worldwide concern for the need of additional and sustainable water resources to satisfy demographic growth and economic development. A hydrochemical and geoelectrical investigation was conducted in the El-Omayed area in the northwestern coast of Egypt. The aim of the study was to delineate different water-bearing formations, provide a general evaluation of groundwater quality, and identify the recharge sources in aquifers. Thirty-seven water samples were collected and chemically analyzed from the sand dune accumulations and oolitic limestone aquifers. Fifteen profiles of vertical electrical soundings (VESs) were obtained in the oolitic limestone aquifer to examine the variations of subsurface geology and associated groundwater chemistry. The groundwater reserves in the El-Omayed area are mainly contained in sand dune accumulations and oolitic limestone aquifers. The aquifer of sand dune accumulations contains freshwater of low salinity (average total dissolved solids (TDS)?=?974 mg/l). Groundwater of oolitic limestone aquifer is slightly brackish (average TDS?=?1,486 mg/l). Groundwater of these aquifers can be used for irrigation under special management for salinity control, and regular leaching as indicated by electrical conductivity and sodium adsorption ratio. Results of VES interpretation classified the subsurface sequence of oolitic limestone aquifer into four geoelectric zones, with increasing depth, calcareous loam, gypsum, oolitic limestone, and sandy limestone. Oolitic limestone constitutes the main aquifer and has a thickness of 12–32 m.     

Widespread microbiological groundwater contamination in the South-eastern Salento (Puglia-Italy)

In the Salento peninsula (Puglia Region, South-East Italy), underground waters are a fundamental resource for the population because they constitute the principal reservoir for drinking water and irrigation. They are, however, affected by overexploitation. The risk factors in the Salento arise mainly from anthropic activities, especially tourism and agriculture (leaking wells, sewage and inadequate waste disposal procedures). The Southern Salento is recognized to be at high risk of pathologies characterised by oral-faecal transmission. From 2001 to 2009 the incidence of typhoid fever in the Salento was 12.11/100,000 inhabitants as against 2.91 in Italy. Enteritis caused by rotaviruses is an important cause of hospitalization of paediatric-aged children in the Salento, with high social costs. An effective monitoring system for the conservation and management of water bodies and the protection of public health is therefore fundamental. The present study sought to determine the microbiological and chemical-physical quality of groundwater in the Salento and to analyse the factors associated with contamination. The results indicated widespread pollution from salt and microbial contamination. Contamination from faecal microorganisms posed a significant risk of human infection in 100% of samples. Furthermore, the water was unsuitable even for irrigation in a high percentage of cases (31.8%), which is of considerable significance given that agriculture is one of the most important economic activities in the area under study. The high salt concentration was probably due to excessive extraction of water for intensive irrigation, especially in summer. Under these circumstances, some of mitigation activity is necessary. Furthermore, it would be advisable to decrease the pollution load from anthropic activities in the territory and to reduce water consumption in order to conserve groundwater resources especially.     

MONITORING OF SPATIAL AND TEMPORAL HYDROCHEMICAL CHANGES IN GROUNDWATER UNDER THE CONTAMINATING EFFECTS OF ANTHROPOGENIC ACTIVITIES IN MERSIN REGION, TURKEY

The development of groundwater resources for water supply is a favored way in Turkey. The Berdan alluvial aquifer in Mersin is particularly productive, but little is known about the natural phenomena that govern the groundwater quality and the contamination sources in this region. During 2001 and 2002, water samples for chemical analysis were obtained from 27 wells and from two points of Berdan River and analyzed by ICP. Main chemical characteristics of sampled groundwater define two aquifers, which were also determined by hydrogeological investigations. The groundwater produced from some of the wells was affected by anthropogenic activities temporally and spatially by seawater intrusion. Berdan River is polluted with the wastewater discharges and river water also influences the groundwater quality.     

Utilizing Successive Linearization Optimization to Control the Saltwater Intrusion Phenomenon in Unconfined Coastal Aquifers in Crete,Greece

In the present work, a simulation-optimization method is employed in order to manage saltwater intrusion in two unconfined coastal aquifers in Crete, Greece. The optimization formulation seeks to maximize groundwater withdrawal rates while maintaining the saltwater intrusion front at the current location or inhibiting it at locations closer to the coast. A combination of a groundwater flow model (MODFLOW) with the Ghyben-Herzberg saltwater front approximation and a sequential implementation of the Simplex algorithm (GWM) are employed. The results show that under the current pumping strategies, the saltwater intrusion front will continue to move inland, posing a serious threat to the groundwater quality of these regions. Optimal groundwater withdrawal scenarios that take into consideration the water needs of the local communities and environmental concerns are presented and discussed. In both case studies, significant reductions in pumping are required in order for the saltwater intrusion front to retract closer to the shoreline.     

Fluoride, boron and nitrate toxicity in ground water of northwest Rajasthan, India

The study was carried out to access the fluoride, boron, and nitrate concentrations in ground water samples of different villages in Indira Gandhi, Bhakra, and Gang canal catchment area of northwest Rajasthan, India. Rural population, in the study site, is using groundwater for drinking and irrigation purposes, without any quality test of water. All water samples (including canal water) were contaminated with fluoride. Fluoride, boron, and nitrate were observed in the ranges of 0.50–8.50, 0.0–7.73, and 0.0–278.68 mg/l, respectively. Most of the water samples were in the categories of fluoride 1.50 mg/l, of boron 2.0–4.0 mg/l, and of nitrate <?45 mg/l. There was no industrial pollution in the study site; hence, availability of these compounds in groundwater was due to natural reasons and by the use of chemical fertilizers.     

Hydrogeochemical features of groundwater of semi-confined coastal aquifer in Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran

Hydrogeochemical data of groundwater from the semi-confined aquifer of a coastal two-tier aquifer in Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran reveal salinization of the fresh groundwater (FGW). The saline groundwater zone is oriented at an angle to both Caspian Sea coastline and groundwater flow direction and extends inland from the coastline for more than 40 km. Spearman’s rank correlation coefficient matrices, factor analysis data, and values of C ratio, chloro-alkaline indices, and Na⁺/Cl^? molar ratio indicate that the ionic load in the FGW is derived essentially from carbonic acid-aided weathering of carbonates and aluminosilicate minerals, relict connate saline water, and ion exchange reactions. Saline groundwater samples (SGWS) (n?=?20) can be classified into two groups. SGWS of group 1 (n?=?17) represent the saline groundwater zone below the Caspian Sea level, and salinization is attributed essentially to (1) lateral intrusion of Caspian seawater as a consequence of (a) excessive withdrawal of groundwater from closely spaced bore wells located in the eastern part of the coastal zone and (b) imbalance between recharge and discharge of the two-tier aquifer and (2) upconing of paleobrine (interfaced with FGW) along deep wells. SGWS of this group contain, on average, 7.9 % of saltwater, the composition of which is similar to that of Caspian seawater. SGWS of group 2 (n?=?3) belong to the saline groundwater zone encountered above the Caspian Sea level, and salinization of the groundwater representing these samples is attributed to irrigation return flow (n?=?2) and inflow of saline river water (n?=?1).