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The present study presents a conceptual model of the chemical evolution of Canadian Shield groundwater that includes major, minor and trace elements. Four (4) stages of the natural chemical evolution of groundwater are examined: Stage 1- infiltration of rainwater; Stage 2- evolution of recharge water, Stage 3a-salinization by Water/Rock interaction, and Stage 3 b-salinization by Water/Clay interaction. The approach proposed is based on a standard of reference called the ‘Water Maturation Index’ (WMI) that establishes standardized concentration values for specific chemical elements occurring in groundwater. The WMI was developed to describe the natural process of multiparameter enrichment/depletion through ongoing salinization from a reference water (rainwater in this study). It is concluded from our study that to better understand the mixing dynamics and contribution of compositional hydrogeochemical poles (endmembers) in an area of the Canadian Shield that has experienced a post-glacial marine event, a groundwater sampling campaign should minimally include the major elements: chlorides, bicarbonates, sulphates, sodium, potassium, magnesium and calcium, to which should be added in all cases the minor and trace elements: iron, manganese, bromides, lithium, strontium, boron, fluorides, molybdenum, nitrite-nitrate, ammonium and silica. Analyzing all these elements together would allow a better understanding of the origin of the chemistry of sampled groundwater, without necessarily requiring isotopic analyses. This study also highlights the importance of using a passive or low-flow sampling protocol to limit anthropogenic disturbance of the natural environment during sampling. Finally, this study improves an existing conceptual model of the chemical evolution of groundwater for the study area. more...

Determining the aquifer vulnerability to pollution is of paramount importance for devising precautionary groundwater protection measures and for land use planning. In this study, we aim to draw a comparison between the intrinsic vulnerability reflected in the hydrogeological conditions and specific vulnerability addressing the vulnerability of an aquifer to a specific contaminant. In consequence, we would be able to quantify their prediction accuracy. To that end, we quantified the groundwater vulnerability for an overexploited aquifer in southern India by means of three indicators including DRASTIC (Depth to water, netRecharge,Aquifer media,Soil media,Topography,Impact of vadose zone, and hydraulicConductivity), modified DRASTIC, and Susceptibility Index (SI). The accuracy of the methods was evaluated using a GIS-based index-overlay approach. Temporal variations in climatic conditions influence the fluctuations in groundwater levels during various seasons which has been rarely considered in aquifer vulnerability studies. This study incorporated, therefore, the spatio-temporal variation in groundwater level in predicting intrinsic and specific vulnerability. Sensitivity and uncertainty analyses were conducted to assess the relative importance of input parameters required for the indicators. Results showed that the lithology of the aquifer was found to be the most sensitive input. A comparison of the three indicators demonstrated that the vulnerability maps from DRASTIC and SI showed the greatest difference. In contrast, modified DRASTIC and SI indicated the greatest similarity, which should be ascribed to the inclusion of the land use factor., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023) more...

High fluoride in drinking water is a rising concern due to its adverse impacts on human health. Spatial mapping coming to the fore to identify fluoride contaminated areas for more effective groundwater management is highly dependent on Spatial InterpolationMethods (SIMs). Therefore, although SIMs have often been used to evaluate the groundwater quality, their efficacy has been poorly documented. To that end, we aim to address this research gap by evaluating the accuracy and uncertainty of nine SIMs, which are applied to a large-scale dataset (n > 13,000) of fluoride concentration at the regional level in India. Our findings revealed that deterministic methods provided a more reliable prediction of fluoride contaminated areas than the stochastic methods. More specifically, inverse distance weighted, and local polynomial interpolation methods showed superior prediction than other methods. Three validation methods including leave-one-out cross validation, hold-out validation and validation with an independent dataset were adopted to evaluate the accuracy of interpolation. As establishing and more importantly maintaining a viable monitoring network of piezometers, especially in remote areas are potentially costly, relying on SIMs is inevitable. It is of paramount importance, therefore, to consider factors that influence the accuracy and uncertainty of SIMs, which varies widely based on the dataset itself i.e. its size, density, distribution, measured range, and smoothing and border effects., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023) more...

A three-dimensional variable-density finite element model was developed to quantify the impact of groundwater over use on submarine groundwater discharge (SGD). The model was applied to the Arani-Korttalaiyar river basin, north of Chennai, India. This region has an upper unconfined and lower semi-confined aquifer extending up to 30 km inland from the coast and beyond this distance; the two aquifers merge and become a single unconfined aquifer. The model simulated that during the period from 2000 to 2012, the flux of seawater to the aquifer has increased from 17,000 to 24,500 m3/day due to over-exploitation of groundwater from the semi-confined aquifer. Where as in the unconfined aquifer, SGD has been taking place. Scenarios showing the impact of newly constructed managed aquifer recharge structures, 10% additional increase in rainfall recharge, and termination of pumping from five well-fields on the groundwater conditions in the area were studied. The model predicted a SGD of 85,243 m3/day from the unconfined aquifer and 22,414 m3/day from the semi-confined aquifer by the end of 2030. By adopting managed aquifer recharge methods, seawater intrusion (rate of 4,408 m3/day) can be reduced and SGD (rate of 22,414 m3/day) increased. The rate of SGD increase and the movement of seawater to aquifer can be completely prevented in the semi-confined aquifer by adopting these management options by 2030. Findings from this study have enhanced the understanding of SGD and water budget, which can be used by decision-makers for the sustainable management of groundwater resources in coastal aquifers. more...

The present study focused on the estimation of submarine groundwater discharge (SGD) and the effects of nutrient fluxes due to the SGD process. The parameters of SGD such as magnitude, character, and nutrient flux in Punnakayal region of South East coast of India were evaluated using multiple tracers of groundwater inputs in 2019. It was found that the elevated values for the tracers in the study area, displayed a gradational change in the values as move from estuarine part to the offshore. Simultaneous occurrence of fresh and saline SGD is observed on the study sites. Also, indicated that the SGD fluxes ranged from 0.04 to 0.12 ​m3 ​m−2 ​d−1 ​at the estuary and 0.03–0.15 ​m3 ​m−2 ​d−1 ​at the groundwater site. A substantially increased value for 222Rn activities is distinguished in the estuary to values over 312 dpm L−1. Nutrient embellishments were generally greatest at locations with substantial meteoric elements in groundwater; however, the recirculation of saltwater through the geological formation could provide a way of transferring terrestrially-derived nutrients to the coastal zone at many places. more...

The main objective of the study is to evaluate the hydrogeochemical processes and potential health risk assessment for humans in groundwater of Maputaland coastal aquifer, South Africa. In this study, 53 and 42 groundwater samples were collected from bore wells during 2018 and 2019 and were analysed for major ions, minor ions, nutrients and trace metals. Na–Cl water type was dominant in groundwater followed by Ca–HCO3. Cross plots revealed that ion exchange, reverse ion exchange, silicate weathering, seawater mixing and anthropogenic inputs from agricultural activities govern the groundwater chemistry. GIS methods were adopted to produce spatial distribution maps of major ions through which locations of groundwater contamination and the intensity of hydrogeochemical processes were identified. Mean concentration of trace metals were in the order: Zn > Li > Al > Fe > Mn > Cu > Pb > As > Co > Cd in 2018, Fe > Zn > Mn > Sr > B > Pb > Cu > Co > Cr > Cd > Ag > Al > Ni in 2019. Most of the trace metals were found to be within the WHO standards for drinking water except Cd, Zn, Pb, Mn, Al and Fe. Health risk assessment of trace metals in groundwater via ingestion and dermal absorption pathways were carried out. Hazard Quotients (HQs) and Hazard Index (HI) of all trace metals were below 1, except HQingestion and HI for Co and Pb which were greater than 1 in children. This suggests that these metals pose adverse risks to local people, and children were more sensitive to risks than adults. HI values for adults and children were medium indicating high risk. This is the first baseline study conducted in the study area which identifies the chemical characterization and the potential health risk due to trace metals contamination. more...

Remote sensing, geophysical, geological and hydrogeological methods were used to characterise the aquifer of a proposed uranium mining and tailings pond area in India. Examination of lithologs show uranium occurrence at the Eparchaean unconformity at a depth of about 50 to 60 m below the surface. Resistivity studies showed four distinct zones- top soil, highly weathered, moderately weathered/fractured rock and massive rock. Wells tap groundwater from the weathered and fractured zones. Highly weathered nature of the intrusives, dykes and faults do not allow them to act as barriers to groundwater flow. Rainfall is the major source of groundwater recharge apart from irrigation return flow. Recharge to unconfined aquifers is primarily by downward seepage of rainfall through the unsaturated zone. Groundwater flows towards southeast. Pumping tests resulted in hydraulic conductivity of this aquifer ranging from 5.4 to 19.3 m/d. Infiltration rates were obtained at 1.5 and 2.3 m/d for clayey residual unconsolidated materials and 3.7 and 5.2 m/d for sandy residual unconsolidated materials. Secondary data were used to verify the results of field tests and investigations. Results from this study were also successfully used in radionuclide and geochemical modelling of the effects of leaching from the tailings pond on groundwater quality and its impact on human health. This detailed study provides a wider understanding of the sub-surface characteristics of the proposed uranium mining and tailings pond area which offers useful information for future research and development activities. more...

The present study first describes the variations in concentrations of 12 chemical elements in groundwater relative to salinity levels in Southern Quebec (Canada) groundwater systems, and then uses this data to develop an empirical predictive model for evaluating groundwater chemical composition relative to salinity levels. Data is drawn from a large groundwater chemistry database containing 2608 samples. Eight salinity classes were established from lowest to highest chloride (Cl) concentrations. Graphical analyses were applied to describe variations in major, minor, and trace element concentrations relative to salinity levels. Results show that the major elements were found to be dominant in the lower salinity classes, whereas Cl becomes dominant at the highest salinity classes. For each of the major elements, a transitional state was identified between domination of the major elements and domination of Cl. This transition occurred at a different level of salinity for each of the major elements. Except for Si, the minor elements Ba, B, and Sr generally increase relative to the increase of Cl. The highest Mn concentrations were found to be associated with only the highest levels of Cl, whereas F was observed to be more abundant than Mn. Based on this analysis of the data, a correlation table was established between salinity level and concentrations of the chemical constituents. We thus propose a predictive empirical model, identifying a profile of the chemical composition of groundwater relative to salinity levels, to help homeowners and groundwater managers evaluate groundwater quality before resorting to laborious and costly laboratory analyses. more...

A water and soil quality baseline study was carried out across the ~ 4500 km2 Vientiane Plain in Lao PDR. Eight water quality and nine soil parameters were analysed using field kits at 95 sites in March 2015. Elevated electrical conductivity and chloride were apparent at two sites due to geogenic leaching from the marine rock-salt present in some areas. Groundwater was acidic in most locations. Nitrate and faecal contamination were also observed from nitrogenous fertilizers (diffuse) and from leaky sewage pits (localised) respectively. Soil quality is neither nutrient deficient nor does it pose a threat to plant growth. Where groundwater is used for drinking, removal of bacterial contamination by simple filtration or boiling is sufficient. In the absence of a functional monitoring network in the Vientiane Plain, periodic surveys of this kind should be performed. The results should be made widely available to the relevant government departments and other stakeholders for better management of the land and water resources. more...

The objective of this study is to develop a Fluoride Index for mitigation of geogenic contamination by Managed Aquifer Recharge (FIMAR). This index was tested by applying to the Pambar river basin in southern India. About 40% of the study area had fluoride >1.5 mg/L, contributed from the dissolution of fluorite, fluorapatite, biotite and hornblende. The relationship between groundwater level and fluoride concentration exhibited two types of relationship. In shallow wells, groundwater recharge during monsoon increases the groundwater level and dilutes the fluoride concentration. During summer, evaporation decreases the groundwater levels and increases the fluoride content. In deep wells, the fluoride-rich salts that is deposited in the unsaturated zone due to evaporation in the pre-monsoon season is flushed during groundwater recharge and thus, the fluoride concentration increases with increase in groundwater level. This relationship was used as a key layer in FIMAR. Overlay analysis including the well type derived from the groundwater level and fluoride fluctuation, average fluoride concentration, geology, geomorphology, soil, drainage density, land use, lineament density and thickness of the weathered zone indicated 30% of the area was suitable for MAR to mitigate fluoride contamination. Since the construction of new MAR structures is cost-intensive, it is proposed to rejuvenate the existing ponds in the areas identified by FIMAR to induce recharge and dilute fluoride concentration. The positive impact was confirmed using numerical and geochemical modelling. This proves that FIMAR can be used as a planning tool in fluoride endemic areas and that the future MAR methods will be beneficial to mitigate geogenic fluoride contamination. more...

Importing food products is associated with the simultaneous transfer of virtual water required for the production of these products. This reduces water resource depletion in the importing country and offers water and food security. The objective of this study is to quantify the water savings and water losses due to virtual water import by India from 1986 to 2013 based on 203 products. Long-term average virtual water import from partner countries is 20.2 Bm3/y. Crop products consume the largest portion of imported virtual water (17.7 Bm3/y) followed by industrial products (2.4 Bm3/y). Livestock products contribute a smaller amount to virtual water import (0.1 Bm3/y). If these products were produced in India instead of being imported, India would have used 31 Bm3/y of its water resources. Thus, the import of products by India leads to 10.8 Bm3/y of global water savings. Importing products from Africa leads to global water losses and most virtual water is saved due to import from South America. Based on the water saved/ lost, the trade partnership of India with partner countries could be classified as mutually beneficial, partially beneficial, unsustainable and pressured. India can amend its trade relations with the partners based on this classification. India’s trade with other countries should consider the water availability in the exporting countries and the comparison between the virtual water required to import the products and to self-produce. Only such a balanced approach can help to sustainably manage the global and national water resources. The present study, however, targets only on the virtual water imports of India and the strategies that the nation could adopt from its own perspective. In order to develop a policy framework, the virtual water export of India should also be considered. more...

The DRASTIC index used to assess the vulnerability of aquifers to contamination, has been subject to various adjustments to improve its reliability. These adjustments include adding and/or eliminating certain aquifer factors and modifying the factor weights. Nonetheless, there is no consensus about which factors, or their respective weights, are most important for assessing aquifer vulnerability. In the present study, we propose an operational methodology that: (1) identifies the relevant factors for assessing aquifer vulnerability to contamination; and (2) determines the relative importance of the selected factors. We applied this approach to a large data set of granular aquifers from a region in Canada, which includes information for DRASTIC factors, combined with groundwater quality and land-use data. We found that for our study region, topography (terrain-slope) is an irrelevant factor for assessing the vulnerability of aquifers to contamination. On the other hand, the relevant factors ranked according to their relative importance (from highest to lowest), are (1) water table depth; (2) hydraulic conductivity; (3) characteristics of vadose zone materials; and (4) recharge. Our approach can serve as an initial step for identifying the relevant aquifer factors when assessing aquifer vulnerability and determining the relative importance of the relevant factors to validate weights attributed to these factors. Our methodology can help adapt index-based methods of aquifer vulnerability assessment to a range of study regions. more...

The purpose of this study is to understand the impact of coastal groundwater over-exploitation on the variations in submarine groundwater discharge (SGD) flux rate and seawater exchange flux across the seabed. As a case study, numerical modelling techniques were applied to a complex multi-aquifer system located north of Chennai, India, which has been affected since the mid-1970s by overexploitation and seawater intrusion. Because of the relatively high hydraulic conductivity, the model shows a higher amount of seawater inflow in the central part of the region. From 2000 to 2012, the movement of seawater has increased from 17,000 m3/day to 24,500 m3/day due to groundwater overexploitation from the semi-confined aquifer. However, the quantum of flux from the sea to the aquifer has been reduced from the year 2006 due to the termination of pumping from a well field supplying a part of the city’s water supply. Model simulations show that fresh groundwater of 43,312 m3/day and saltwater of 43,815 m3/day will be discharged to the aquifer by the end of 2030. In addition to the prevailing condition, various management scenarios were also predicted to prevent the degradation of groundwater quality due to seawater intrusion. By adopting managed aquifer recharge methods, saltwater intrusion (rate of 4408 m3/day) can be reduced and SGD (rate of 22414 m3/day) rate increased. Findings from this study are expected to enhance the understanding of SGD and freshwater budget in coastal areas and in creating integrated coastal management plans. more...

Assessment of historical hydro-meteorological drought is important to develop a robust drought monitoring and prediction system. This study aims to assess the historical hydro-meteorological drought of the Johor River Basin (JRB) from 1975 to 2010, an important basin for the population of southern Peninsular Malaysia and Singapore. The Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) were selected to represent the meteorological and hydrological droughts, respectively. Four absolute homogeneity tests were used to assess the rainfall data from 20 stations, and two stations were flagged by these tests. Results indicate the SPI duration to be comparatively low (3 months), and drier conditions occur over the upper JRB. The annual SSI had a strong decreasing trend at 95% significance level, showing that human activities such as reservoir construction and agriculture (oil palm) have a major influence on streamflow in the middle and lower basin. In addition, moderate response rate of SSI to SPI was found, indicating that hydrological drought could also have occurred in normal climate condition. Generally, the El Nino-Southern Oscillation and Madden Julian Oscillation have greater impacts on drought events in the basin. Findings of this study could be beneficial for future drought projection and water resources management. more...

Satellite and reanalysis precipitation products can be potentially used for monitoring and analysing drought patterns in tropical regions. In this study, Tropical Measuring Mission Multisatellite Precipitation Analysis monthly product (3B43) and the product from National Centers for Environmental Prediction Climate Forecast System Reanalysis (NCEP-CFSR) are analysed for precipitation estimation and drought assessment over Singapore. The evaluation is conducted by comparing the field observations from 22 precipitation gauges from 1998 to 2014. The Standardized Precipitation Index recommended by the World Meteorological Organization was used for the drought assessment. Results show that 3B43 performed better in monthly, seasonal, and annual precipitation estimations compared to NCEP-CFSR. Both products show an underestimation of monthly and annual precipitation. Similarly, 3B43 also outperformed NCEP-CFSR in drought monitoring over Singapore. The 3B43 product successfully detected major droughts tha... more...

Indirect trade of water (virtual water) through export of crop and livestock products may pose a risk to water resources in the exporting country. Management strategies can be framed by identifying the partner countries and the current status of water resources in these countries. This study for the first time analyses the virtual water trade of India considering the specific virtual water contents of crop and livestock products from all partner countries from 1986 to 2013 (28 years). Average virtual water export of India is 59 Bm 3 /y and virtual water import is 32.6 Bm 3 /y. Net virtual water import (−26.4 Bm 3 /y) indicates India is a major exporter. Oil, cereals, industrial products (cotton, jute, hides etc.) and semi-luxury goods contribute to 79% of virtual water export. Oil and nuts contribute to 71% of virtual water import. Decline in virtual water trade due to slow economic growth and impact of floods are reflected in the inter-annual variation. Highest virtual water trade from India is to countries in Asia (74% as virtual water export and 59% as virtual water import). Virtual water import to India are mainly through palm oil, cashew nuts, soybean, sunflower oil, wheat, rubber, cotton and pulses. Water footprint of India has increased by 1.3 times in 28 years. Strategies for sustainable management of water resources in India and the partner countries should aim at reducing the import of water-intensive goods from water-scarce countries and increasing import of water-intensive goods from water-abundant countries. more...

Analyzing the driving factors of regional carbon emissions is important for achieving emissions reduction. Based on the Kaya identity and Logarithmic Mean Divisia Index method, we analyzed the effect of population, economic development, energy intensity, renewable energy penetration, and coefficient on carbon emissions during 1990&ndash, 2016. Afterwards, we analyzed the contribution rate of sectors&rsquo, energy intensity effect and sectors&rsquo, economic structure effect to the entire energy intensity. The results showed that the influencing factors have different effects on carbon emissions under different stages. During 1990&ndash, 2000, economic development and population were the main factors contributing to the increase in carbon emissions, and energy intensity was an important factor to curb the carbon emissions increase. The energy intensity of industry and the economic structure of agriculture were the main factors to promote the decline of entire energy intensity. During 2001&ndash, 2010, economic growth and emission coefficient were the main drivers to escalate the carbon emissions, and energy intensity was the key factor to offset the carbon emissions growth. The economic structure of transportation, and the energy intensity of industry and service were the main factors contributing to the decline of the entire energy intensity. During 2011&ndash, 2016, economic growth and energy intensity were the main drivers of enhancing carbon emissions, while the coefficient was the key factor in curbing the growth of carbon emissions. The industry&rsquo, s economic structure and transportation&rsquo, s energy intensity were the main factors to promote the decline of the entire energy intensity. Finally, the suggestions of emissions reductions are put forward from the aspects of improving energy efficiency, optimizing energy structure and adjusting industrial structure etc. more...

The origin of groundwater and the processes controlling its chemical composition in complex coastal aquifers are of interest, as about 44% of the world’s population lives in coastal areas. Groundwater over-exploitation in the highly urbanized coastal regions has exerted pressure on these aquifers, leading to seawater intrusion. This study aimed to identify (1) the complex relationship between natural and anthropogenic factors, and (2) the hydrogeochemical processes controlling the groundwater chemistry in an over-stressed coastal aquifer of southern India. The results indicate an increase in the extent of seawater intrusion from 4 km in 1969 to 17 km in 2014. Major hydrogeochemical processes controlling the aquifers are evaporation, ion exchange and dissolution of aluminosilicates, gypsum, halites and calcites. The integrated use of field investigation with hydrochemical, isotopic and hydrogeochemical modelling techniques allowed a conceptual model of the groundwater salinization process over 46 years to be developed as a basis for designing sustainable management measures. more...

Comprehensive assessment of the virtual water trade of Germany with the world is performed and the national water footprint through the trade of crop and livestock products from 1991 to 2016 is assessed. Virtual water flows based on 328 products with more than 200 countries indicate Germany as a net virtual water importer. Average virtual water import was 100.5 Bm3/y, virtual water export was 60.2 Bm3/y and net virtual water import was 40.3 Bm3/y. Trade patterns of virtual water transfer differ for the various commodity types. Trade between Germany and the world implies a global water loss of 5.9 Bm3/y. This study portrays that trade between countries is not only related to the economics but interlinked with the agricultural water use and management practices of the respective nations. Sustainable management of the resources will require a collective consideration of the agricultural, water and economic sectors while developing strategies. more...

Drought, one of the most common natural disasters that have the greatest impact on human social life, has been extremely challenging to accurately assess and predict. With global warming, it has become more important to make accurate drought predictions and assessments. In this study, based on climate model data provided by the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), we used the Palmer Drought Severity Index (PDSI) to analyze and project drought characteristics and their trends under two global warming scenarios&mdash, 1.5 &deg, C and 2.0 &deg, C&mdash, in Central Asia. The results showed a marked decline in the PDSI in Central Asia under the influence of global warming, indicating that the drought situation in Central Asia would further worsen under both warming scenarios. Under the 1.5 &deg, C warming scenario, the PDSI in Central Asia decreased first and then increased, and the change time was around 2080, while the PDSI values showed a continuous decline after 2025 in the 2.0 &deg, C warming scenario. Under the two warming scenarios, the spatial characteristics of dry and wet areas in Central Asia are projected to change significantly in the future. In the 1.5 &deg, C warming scenario, the frequency of drought and the proportion of arid areas in Central Asia were significantly higher than those under the 2.0 &deg, C warming scenario. Using the Thornthwaite (TH) formula to calculate the PDSI produced an overestimation of drought, and the Penman&ndash, Monteith (PM) formula is therefore recommended to calculate the index. more...

The realization of carbon emissions peak is important in the energy base area of China for the sustainable development of the socio-economic sector. The STIRPAT model was employed to analyze the elasticity of influencing factors of carbon emissions during 1990&ndash, 2010 in the Xinjiang autonomous region, China. The results display that population growth is the key driving factor for carbon emissions, while energy intensity is the key restraining factor. With 1% change in population, gross domestic product (GDP) per capita, energy intensity, energy structure, urbanization level, and industrial structure, the change in carbon emissions was 0.80%, 0.48%, 0.20%, 0.07%, 0.58%, and 0.47%, respectively. Based on the results from regression analysis, scenario analysis was employed in this study, and it was found that Xinjiang would be difficult to realize carbon emissions peak early around 2030. Under the condition of the medium-high change rates in energy intensity, energy structure, industrial structure, and with the low-medium change rates in population, GDP per capita, and urbanization level, Xinjiang will achieve carbon emissions peak at of 626.21, 636.24, 459.53, and 662.25 million tons in the year of 2030, 2030, 2040, and 2040, respectively. At last, under the background of Chinese carbon emissions peak around 2030, this paper puts forward relevant policies and suggestions to the sustainable socio-economic development for the energy base area, Xinjiang autonomous region. more...

Mapping groundwater contaminants and identifying the sources are the initial steps in pollution control and mitigation. Due to the availability of different mapping methods and the large number of emerging pollutants, these methods need to be used together in decision making. The present study aims to map the contaminated areas in Richards Bay, South Africa and compare the results of ordinary kriging (OK) and inverse distance weighted (IDW) interpolation techniques. Statistical methods were also used for identifying contamination sources. Na–Cl groundwater type was dominant followed by Ca–Mg–Cl. Data analysis indicate that silicate weathering, ion exchange and fresh water–seawater mixing are the major geochemical processes controlling the presence of major ions in groundwater. Factor analysis also helped to confirm the results. Overlay analysis by OK and IDW gave different results. Areas where groundwater was unsuitable as a drinking source were 419 and 116 km2 for OK and IDW, respectively. Such diverse results make decision making difficult, if only one method was to be used. Three highly contaminated zones within the study area were more accurately identified by OK. If large areas are identified as being contaminated such as by IDW in this study, the mitigation measures will be expensive. If these areas were underestimated, then even though management measures are taken, it will not be effective for a longer time. Use of multiple techniques like this study will help to avoid taking harsh decisions. Overall, the groundwater quality in this area was poor, and it is essential to identify alternate drinking water source or treat the groundwater before ingestion. more...

This study aims to use fluoride as an additional indicator for seawater intrusion apart from the known effective geochemical indicators such as EC, TDS, sodium, chloride and bromide. Groundwater in a coastal part of Arani-Koratalaiyar river basin located north of Chennai, Tamil Nadu, India was assessed to determine its suitability for domestic purpose and to delineate the region affected by seawater intrusion. Fluoride concentration in groundwater samples from forty nine locations varied from 0.02 mg/l to 2.9 mg/l with an average of 0.5 mg/l. As per the Bureau of Indian Standards, the permissible range of fluoride in drinking water is 0.6–1.5 mg/l. Fluoride concentration in groundwater of this area exceeds 1.5 mg/l in 6% of the groundwater samples and is below 0.6 mg/l in 74% of the groundwater samples. There is no known geological source for fluoride in this area. Spatial variation in fluoride concentration in groundwater indicates that the coastal areas have comparatively high fluoride due to seawater intrusion which was similar in comparison with EC and bromide concentration measured in groundwater. This study indicates that fluoride can be used as an indicator of seawater intrusion in coastal areas. more...

Groundwater is an important source of fresh water for the world. In recent times groundwater has contributed a significant portion to the piped water supplies of many cities. Compared to rural areas, groundwater in urban areas is vulnerable to contamination from multiple sources and pathways. Potential sources of groundwater contamination are local geology, industries, agricultural chemicals (fertilizers, pesticides, fungicides, herbicides, and insecticides), sewage systems, heavy groundwater pumping, municipal waste landfills, electronic waste, underground storage tanks, polluted surface water and soil, road salts, effects of climate change, etc. Major contaminants in groundwater include arsenic, fluoride, nitrate, phosphates, heavy metals (lead, cadmium, chromium, mercury, etc.), pathogenic microorganisms, volatile organic compounds, and emerging organic contaminants. This chapter describes the various sources and selected contaminants that pollute urban groundwater. A case study of groundwater pollution in an urban area in India is also presented. more...

The suitability of groundwater for drinking and irrigation purposes was evaluated using Water Quality Index, GIS and Multivariate Statistical method in a part of Nalgonda District, Telangana, India Forty-five groundwater samples were collected from wells on January, 2010. On-site field measurements of pH, electrical conductivity (EC), and temperature, and the laboratory analysis of major ions were carried out. Six groundwater types are dominant: Ca-HCO3, Na-Cl, mixed Ca-Na-HCO3, mixed Ca-Mg-Cl, Ca-Cl, and Na-HCO3. Spatial variation maps were developed for physicochemical parameters by using inverse distance weighted interpolation method and grouping analysis. These maps are categorized as desirable, permissible, and not permissible according to the World Health Organization (WHO) standard. The water-quality index map comprised a 443 km2 area categorized as good for drinking purposes. Groundwater is suitable for irrigation by SAR, EC, Na%, PI, RSC, MR, and USSL classification and Wilcox methods. Multivariate statistical techniques of correlation matrix, factor analysis, and cluster analysis evaluated the hydrochemical variations and the driving factors as well as the hydrogeochemical characteristics of the aquifer. The final section of this study concludes that groundwater quality is mainly affected by water-rock interactions, intensive agricultural activities, and the anthropogenic activity in the study area. more...

Remote sensing and GIS tools have broadly helped hydrogeologists to delineate the groundwater prospective zones for watershed development and management. The origin, movement and existence of groundwater depends on several factors such as slope, drainage density, land use, geology, lineament density and geomorphology. Based on these, the mapping and identification of groundwater potential zones were carried out in a part of Nalgonda district, Telangana, India. The regions were categorised as high, moderate and low groundwater potential, and they were validated with the groundwater levels and yield of wells located in the corresponding zones. Extensive possibility for watershed development is possible in 41 % of the total 724 km2 and 46 % of the area offers moderate options. Any groundwater management project implemented in these favourable areas will bring maximum benefit. Similar studies should be considered necessary before designing a water resource development activity as it will reduce the cost on detailed field visits which are time-consuming. more...

Summary Identification of a suitable overlay and index method to map vulnerable zones for pollution in weathered rock aquifers was carried out in this study. DRASTIC and four models derived from it, namely Pesticide DRASTIC, modified DRASTIC, modified Pesticide DRASTIC and Susceptibility Index (SI) were compared by applying them to a weathered rock aquifer in southern India. The results were validated with the measured geochemical data. This study also introduces the use of temporal variation in the groundwater level and nitrate concentration in groundwater as input and for validation respectively to obtain more reliable and meaningful results. Sensitivity analysis of the vulnerability index maps highlight the importance of one parameter over another for a given hydrogeological setting, which will help to plan the field investigations based on the most or the least influential parameter. It is recommended to use modified Pesticide DRASTIC for weathered rock regions with irrigation practises and shallow aquifers ( more...

Suitability of groundwater for domestic and irrigation purposes as well as its hydrochemical characteristics was estimated in a part of Nalgonda district, Telangana state in southern India. Water samples were collected from 45 wells once every 2 months from March 2008 to January 2010. EC and pH were measured in situ while concentrations of calcium, magnesium, sodium, potassium, sulphate and chloride in groundwater were analysed using ion chromatograph. Carbonate and bicarbonate concentration were determined by acid base titration. General order of dominance of cations in the groundwater of this study area is Na+ > Ca2+ > Mg2+ > K+ while that for anions is HCO3 − > Cl− > SO 4 −2 . Ca–HCO3, Na–Cl, mixed Ca–Na–HCO3 and mixed Ca–Mg–Cl types of groundwater were dominant in this area. Groundwater is generally fresh with medium to high salinity and low alkalinity. Chloride and bicarbonate concentrations were present within the permissible limits for drinking whereas, some samples exceed the permissible limits of the Bureau of Indian Standards for pH, TDS, TH, sodium, calcium, magnesium and sulphate. Potassium exceeded the maximum permissible limits for drinking proposed by World Health Organisation. Sodium adsorption ratio, sodium percentage, residual sodium carbonate and permeability index indicates that the groundwater quality was suitable for irrigation in most parts of the study area. more...

Check dams are often constructed across the rivers to store excess runoff and to improve groundwater recharge. Quality of groundwater around the check dam depends on the chemical and biological characteristics of the water stored in the check dam. The aim of this study is to determine the benefits due to changes in chemical and microbial composition of groundwater during the process of recharge. This study was carried out in and around a check dam constructed across Arani River, Tamil Nadu, India, where people depend on groundwater reserves for domestic and irrigation requirements. Water samples were collected from the river and surrounding wells and were analysed for chemical and microbial contents. WQI based on the chemical composition indicates that the groundwater was good in this area, but microbes such as Escherichia spp., Salmonella spp., Shigella spp. and Clostridium spp. were present. However, the microbial quality of groundwater is far better than the water stored in the check dam. Hence, production wells can be planned at a distance of about 400 m in the east so that the bank filtrate will take at least 60 days to reach the well. This will considerably reduce the microbial load and also the cost of post-treatment. Thus, river bank filtration may be adopted near the check dams so as to maximise well yield and to achieve natural filtration. This will also enable to use a portion of water that otherwise would be lost due to evaporation from the dam. more...

Drought is one of the most hazardous natural disasters for human beings and the environment. Using only rain gauge is insufficient to monitor the drought pattern effectively as it impacts large areas. This situation is more critical on small island countries, with limited rain gauges for monitoring drought pattern over the ocean regions. This study aims to assess the capability of Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) 3B43 product in monitoring drought in Singapore from 1998 to 2014. The Standardized Precipitation Index (SPI) at various time-scales is used for identifying drought patterns. Results show moderate to good correlations between TMPA- 3B43 and rain gauges in the SPI estimations. Besides that, TMPA-3B43 exhibits a similar temporal drought behavior as the rain gauges. These findings indicate the TMPA 3B43 product as a very useful tool to study drought pattern over Singapore. more...

Impact of agricultural activities on groundwater can be determined from the concentration of nutrients present in groundwater. This study was carried out with the aim to assess the minor ions content of groundwater and to identify its sources, spatial, and seasonal variations in a part of the Cauvery River basin, southern India. Groundwater samples were collected from July 2007 to September 2009 and were analyzed for minor ions. These ions were in the order of dominance of nitrate> phosphate> bromide> fluoride> ammonium= nitrite> lithium. The concentration of ions tends to increase towards the coast except for fluoride. Increased concentration of ions identified in shallow wells than in deep wells with an exception of few locations indicates the impact of human activities. Relatively high concentration of agriculture-sourced nitrate was identified which pose a threat to groundwater suitability for agriculture and domestic usage. Combined influence of use of agrochemicals, improper sewage disposal, aquaculture activities, seawater intrusion due to heavy pumping near the coast, and natural weathering of aquifer materials are the major sources. Also, fine grain sediments of this area aid in poor flushing of the ions towards the sea resulting in accumulation of higher concentration of ions. A sustainable management strategy is essential to control the concentration of these ions, especially nitrate. Reduced use of fertilizers, increasing the rainfall recharge for diluting the pollutants in groundwater and maintaining the river flow for sufficiently longer period to reduce dependence on groundwater for irrigation can help to improve the situation. more...

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

The impact of a proposed uranium tailings pond on groundwater quality was assessed by geochemical modelling. Groundwater samples were collected from six dug wells in the Nalgonda district, Andhra Pradesh, in southern India, once every 2 months from March 2008 to January 2010, and analysed for calcium, magnesium, sodium, potassium, chloride, sulphate, carbonate, bicarbonate, and uranium. Prediction of groundwater quality was carried out for 100 years using PHREEQC to assess the effects of infiltration of water from the proposed tailings pond. The sensitivity of the model for variations in porosity, hydraulic gradient, hydraulic conductivity, and concentration of uranium in the tailings was evaluated. Geochemical modelling predicts that if the chemical composition of the tailings water is maintained at about the expected mean concentrations, and an appropriate liner is installed with an infiltration rate ≤1.0 × 10−9 m/s, the concentration of solutes in the groundwater will be increased from present background levels for a down-gradient distance of up to 500 m for the anticipated life of the mine, i.e. 16 years. The concentration of ions in groundwater would exceed background concentrations for up to 100 m at the end of 100 years. This study was used to predict the optimum chemical composition for the tailings and the extent, in terms of time and distance, that the groundwater concentration of various ions would be increased by infiltration of wastes from the tailings pond. more...

Drainage and lineaments play an important role in the flow of groundwater. The objective of this study is to assess the groundwater level and its relation to drainage and lineaments in a hard rock region of a part of Nalgonda district, Andhra Pradesh, southern India. The region predominantly comprise of granites and gneisses. Groundwater level was measured in 42 representative wells in this study area from March 2008 to January 2010 once in every two months. Observed groundwater levels were compared with drainage and dyke density. Groundwater level fluctuation in low drainage density region is generally greater than those in moderate and high drainage density regions. The dykes do not act as barriers for groundwater flow as they are highly weathered. The quantity and flow of groundwater in this region is predominantly controlled by drainage density, intensity of weathering and presence of fractures. Thus the study indicate that the drainage density play a major role in groundwater level fluctuation and as the dykes are weathered, they do not affect the groundwater flow in this shallow unconfined aquifer. more...

Presence of polycyclic aromatic hydrocarbons (PAHs) in the soil and water is of serious environmental concern as they are carcinogenic in nature. The present study was carried out with an aim to identify the presence of PAHs in groundwater of Chennai, Tamil Nadu, India. This is an industrialised area where petrochemical storage tanks are located. Groundwater sampling was carried out in the years 2001, 2011 and 2012 to understand the variation in PAHs content in this area. Concentration of major ions, pH and EC were measured during the year 2001. Of the 24 groundwater samples collected in the year 2001, most of them were alkaline and 62.5 % were not permissible for drinking based on pH and EC, respectively. Influence of seawater was the major reason for the Na–Cl dominant nature of groundwater. TPH and PAHs analysis of groundwater carried out in 2001 and 2011, and physical examination of groundwater in 2012 indicate the increased level of contamination in the eastern part of the study area. The contamination in the eastern part persists because of the fact that groundwater is flowing towards the east and also due to the presence of petrochemical storage tanks near the coast. Thus this area is affected by PAHs pollution which has endured over the past 50 years. An underground storage tank that was functioning in this area was closed about 50 years ago and leakage of PAHs from this tank was reported in the year 1993. However, the present study indicates the decrease in the area of zone of pollution, possibly due to natural flushing of groundwater zone. more...

Nitrate is a common pollutant in surface water and groundwater of agricultural areas. It is essential to monitor this pollutant in groundwater, especially when it is used for drinking purposes without treatment. The present study was carried out in an intensively irrigated area which forms a part of Nalgonda district, Andhra Pradesh, India where groundwater meets all the water needs of the rural population living in this area. The objective was to assess the spatiotemporal variation in the concentration of nitrate in groundwater and soil. Based on the analysis of 496 groundwater samples collected from 45 wells over a period of 2 years from March 2008 to January 2010 by sampling every 2 months, it was observed that groundwater in 242 km2 of the total 724 km2 area had nitrate above the maximum permissible limit of 45 mg/l for drinking purposes. Nitrate concentration in groundwater showed a positive relation with potassium, chloride, and sulfate, indicating their source from fertilizers. Reasons for the high concentration of nitrate in domestic areas were the dumping of animal wastes and leakage from septic tanks. The pH of the soil samples showed that most of the area had basic soil. Apart from pH, organic carbon, available phosphorous, available potassium, ammoniacal nitrogen, and nitrate nitrogen were also analyzed in the 97 soil samples. more...

During floods, human exposure to pathogens through contaminated water leads to the outbreak of epidemic diseases. This research presents the first extensive assessment of surface and groundwater samples collected immediately after a flood (December 2015) and post-flood (April 2016) from the Adyar River of Chennai, a major city in India, for major ions, trace metals, bacterial population, and pathogens. Severe rains in a short period of time resulted in flooding which inundated the wells, allowing the entry of sewage contaminated river water into the groundwater zone. This has led to bacterial counts and chemical ions exceeding Bureau of Indian Standard’s recommended limits in most flood affected areas. Pathogens isolated from the groundwater showed resistance to antibiotics, namely ceftriaxone, doxycycline and nalidixic acid. However, they were sensitive to chloramphenicol, ciprofloxacin, norfloxacin, and tetracycline. Determining the antibiotic susceptibility of pathogens will help in the treatment of humans affected by contaminated water through an appropriate selection of prescribed medication. Machine-accessible metadata file describing the reported data (ISA-Tab format) more...

Groundwater used for domestic purpose without proper treatment should be free from chemical and biological contaminants. This study was carried out to assess the groundwater quality with respect to uranium in a part of Nalgonda district, Andhra Pradesh, India. Groundwater was regularly monitored for uranium concentration by collection of samples once every two months from March 2008 to November 2009 from 44 wells. The concentration of uranium in groundwater ranged from 0.2 to 118.4 ppb. Groundwater is unsuitable for domestic use in 2 % of this area based on the limit of 60 ppb prescribed by the Atomic Energy Regulatory Board of India. However, due the wide variation in limit suggested by different organizations and countries, the no-observed-adverse-effect level and lowest-observed-adverse-effect level (in mg/kg day) was used to understand the dosage of uranium that reaches the people through drinking water pathway. This level varied from 0 to 0.02 mg/kg day and 0 to 0.08 mg/kg day based on an uncertainty factor of 10 and 50 respectively for the mean uranium concentration in groundwater in each well. With an uncertainty factor of 50, 5 groundwater samples had uranium above 0.06 mg/kg day which is the lowest-observed-adverse-effect level. This study showed that with the presence of present level of uranium concentration in groundwater of this area there is no major threat to humans through the drinking water pathway. more...

Extensive hydrogeological investigations followed by three-dimensional groundwater flow and contaminant transport modelling were carried out around a proposed uranium tailings pond at Seripalli in Andhra Pradesh, India, to estimate its radiological impact. The hydrogeological parameters and measured groundwater level were used to model the groundwater flow and contaminant transport from the uranium tailings pond using a finite-element-based model. The simulated groundwater level compares reasonably with the observed groundwater level. Subsequently, the transport of long-lived radionuclides such as 238U, 234U, 230Th and 226Ra from the proposed tailings pond was modelled. The ingrowths of progenies were also considered in the modelling. It was observed that these radionuclides move very little from the tailings pond, even at the end of 10,000 y, due to their high distribution coefficients and low groundwater velocities. These concentrations were translated into committed effective dose rates at different distances in the vicinity of the uranium tailings pond. The results indicated that the highest effective dose rate to members of the public along the groundwater flow pathway is 2.5 times lower than the drinking water guideline of 0.1 mSv/y, even after a long time period of 10,000 y. more...

The present study was carried out with the objective of determining the extent of groundwater pollution caused by tanning industries in Chromepet area located south of Chennai, Tamil Nadu, India. Groundwater samples were collected during January and March 2008 from 36 wells and were analysed for the concentration of various major ions and chromium. Na-Cl was the dominant water type found in this area. Groundwater in this area is not suitable for drinking as it contains elevated concentration of most major ions and chromium. This is due to the recharge of partially treated effluent discharged by tanning industries into open drains. The concentration of chromium was above the permissible limit (0.05 mg/l) in 86% of the groundwater samples. The use of chemicals, such as sodium chloride, sodium sulphate, chromium sulphate etc. during the tanning processes is the major reason for the high concentration of major ions and chromium in groundwater. Hence it is important to regulate the industries and also take measures to reduce the total dissolved solids in the treated effluent before disposal. The groundwater quality of this region can also be improved by adopting rainwater harvesting thereby increasing groundwater recharge. more...

Geochemical processes that take place in the aquifer have played a major role in spatial and temporal variations of groundwater quality. This study was carried out with an objective of identifying the hydrogeochemical processes that controls the groundwater quality in a weathered hard rock aquifer in a part of Nalgonda district, Andhra Pradesh, India. Groundwater samples were collected from 45 wells once every 2 months from March 2008 to September 2009. Chemical parameters of groundwater such as groundwater level, EC and pH were measured insitu. The major ion concentrations such as Ca2+, Mg2+, Na+, K+, Cl−, and SO42− were analyzed using ion chromatograph. CO3− and HCO3− concentration was determined by acid–base titration. The abundance of major cation concentration in groundwater is as Na+ > Ca2+ > Mg2+ > K+ while that of anions is HCO3− > SO42− > Cl− > CO3−. Ca–HCO3, Na–Cl, Ca–Na–HCO3 and Ca–Mg–Cl are the dominant groundwater types in this area. Relation between temporal variation in groundwater level and saturation index of minerals reveals the evaporation process. The ion-exchange process controls the concentration of ions such as calcium, magnesium and sodium. The ionic ratio of Ca/Mg explains the contribution of calcite and dolomite to groundwater. In general, the geochemical processes and temporal variation of groundwater in this area are influenced by evaporation processes, ion exchange and dissolution of minerals. more...