Delineating shallow saline groundwater zones from Southern India using geophysical indicators.

A geophysical survey was conducted over an industrial belt encompassing 80 functional leather factories in Southern India. These factories discharge untreated effluents which pollute shallow groundwater where electrical conductivity (EC) value had a wide range between 545 and 26,600 µS/cm (mean, 3, 901 µS/cm). The ranges of Na(+) and Cl(-) ions were from 46 to 4,850 mg/L (mean, 348 mg/L) and 25 to 10,390 mg/L (mean, 1,079 mg/L), respectively. Geoelectrical layer parameters of 37 vertical electrical soundings were analyzed to demarcate fresh and saline water zones. However, the analysis not did lead to a unique resolution of saline and fresh waters. It was difficult to assign a definitive value to the aquifer resistivity of any area. Thus, geophysical indicators, namely longitudinal unit conductance (S), transverse unit resistance (T), and average longitudinal resistivity (Rs), were calculated for identifying fresh and saline waters. Spatial distributions of S, T, and R s reflected widely varying ranges for the saline and fresh water zones. Further, the empirical relation of formation factor (F) was established from pore-water resistivity and aquifer resistivity for fresh and saline aquifers, which may be used to estimate local EC values from the aquifer resistivity, where well water is not available.

Chloride migration in groundwater for a tannery belt in Southern India.

Groundwater in a tannery belt in Southern India is being polluted by the discharge of untreated effluents from 80 operating tanneries. Total dissolved solids and chloride (Cl(-)) measurements in open wells in the tannery cluster vary from 27,686 to 39,100 and 12,000 to 13,652 mg/l, respectively. A mass transport model was constructed using Visual MODFLOW Premium 4.4 software to investigate the chloride migration in an area of 75.56 km(2). Input to the chloride migration model was a groundwater flow model that considered steady and transient conditions. This model was calibrated with field observations; and sensitivity analysis was carried out whereby model parameters, viz., conductivity, dispersivity, and source concentration were altered slightly, and the effect on calibration statistics was evaluated. Results indicated that hydraulic conductivity played a more sensitive role than did dispersivity. The Cl(-) migration was mainly through advection rather than dispersion. It was found that even if the pollutant load reduced to 50% of the present level, the Cl(-) concentration in groundwater, even after 6 years, would not be reduced to the permissible limit of drinking water in the tannery belt.

Integrated approach for demarcating subsurface pollution and saline water intrusion zones in SIPCOT area: a case study from Cuddalore in Southern India.

This paper deals with a systematic hydrogeological, geophysical, and hydrochemical investigations carried out in SIPCOT area in Southern India to demarcate groundwater pollution and saline intrusion through Uppanar River, which flows parallel to sea coast with high salinity (average TDS 28, 870 mg/l) due to back waters as well as discharge of industrial and domestic effluents. Hydrogeological and geophysical investigations comprising topographic survey, self-potential, multi-electrode resistivity imaging, and water quality monitoring were found the extent of saline water intrusion in the south and pockets of subsurface pollution in the north of the study area. Since the area is beset with highly permeable unconfined quaternary alluvium forming potential aquifer at shallow depth, long-term excessive pumping and influence of the River have led to lowering of the water table and degradation of water quality through increased salinity there by generating reversal of hydraulic gradient in the south. The improper management of industrial wastes and left over chemicals by closed industries has led surface and subsurface pollution in the north of the study area.

Assessment of natural groundwater reserve of a morphodynamic system using an information-based model in a part of Ganga basin, Northern India.

Assessment of morphodynamic groundwater reserves is important for the sustainable management of water resources. It is a truth that groundwater resource evaluation is anxious with the ambiguity of its several factors and employing methods. Thus, an information-based model has been hypothesized to assess natural groundwater reserves in a morphodynamic system in a part of the Ganga basin of Northern India, where the spatial variability in natural groundwater reserve exists. Marginal information of rainfall data, and transinformation among the rainfall, and monthly depth to groundwater level measurement at 50 wells in a dense monitoring network were used for evaluating natural groundwater reserve. The results indicate that an average recharge rate is about 246 mm/monsoon and or 32.65% of the seasonal rainfall, and its values are well-correlated with the soil infiltration rate. It has been found that the estimated recharge rates are about 54.08, 45.85, 33.77, 32.48, and 32.14% of the seasonal rainfall in an active flood plain, back swamp, natural levees, flood plain, and palaeochannel, respectively. The calculated annual rainfall input to groundwater reserve is found about 127.98 MCM/monsoon rainfall, which could be employed for sustainable management of groundwater resources in the morphodynamic system of the Ganga river basin.

Geostatistical spatial projection of geophysical parameters for practical aquifer mapping.

Dense data acquisition for 3-D high-resolution aquifer mapping through heliborne transient electromagnetic (HTEM) survey is continually not possible due to various technical and administrative constraints. Consequently, we apply ground geophysical surveys at possibly closer spacing to collect the sub-surface information in the no-fly area, which provides only a regional aquifer picture. In the area near Patna of Northern India, an extent of 18% was covered under the HTEM survey, and the rest was surveyed by ground geophysical methods. Both data are integrated using the theory of regionalized variables. The parameters of multi-aquifers i.e., top of the first aquifer, top of the separating clay layer, top and the bottom of second aquifer, are estimated together with their respective resistivities. The estimations are made at an interval of 250 m, practically an appropriate distance at which dense data generation was carried out using the HTEM survey. The integrated approach generates the data in the no-fly area with the same spatial density as the flown area. With this, we achieved the goal of completing the 3-D aquifer mapping of the entire area with dense data at high spatial resolution. This is a unique finding to manage the handicapped situation in this HTEM surveys, and an aide to overcome such constraints with cost-effectiveness.

Assessment of seawater impact using major hydrochemical ions: a case study from Sadras, Tamilnadu, India.

The impact of seawater intrusion was investigated using major hydrogeochemical ions to evaluate the origin of salinity in Sadras watershed located between Buckingham Canal and Bay of Bengal in the southeastern coast of India. From empirical data collected twice during pre- and post-monsoon seasons, it was found that groundwater was slightly acidic to mildly alkaline, and more than 44% of groundwater samples had EC > 3,000 µS/cm in both the seasons. Results of principle component analysis (PCA) showed that Na( + ), Cl( - ), Mg(2 + ), and SO[Formula: see text] concentrations had the highest loading factor and the samples affected by saline/seawater were separated from the cluster. Hydrochemical processes that accompany the saline/seawater were identified using ionic changes. It was observed during sampling periods that the mixing due to saline/seawater intrusion varied from 4.82-7.86%. Negative values of ionic change (e (change)) for Na( + ) and K( + ) decreased with the increasing fraction of seawater. Furthermore, salinity, sodium adsorption ratio, percentage of sodium Na (%), and exchangeable sodium percentage in well samples showed that groundwater was unsuitable for irrigation purposes.

Anthropogenic nitrate in groundwater and its health risks in the view of background concentration in a semi arid area of Rajasthan, India.

An increased nitrate (NO3-) concentration in groundwater has been a rising issue on a global scale in recent years. Different consumption mechanisms clearly illustrate the adverse effects on human health. The goal of this present study is to assess the natural and anthropogenic NO3- concentrations in groundwater in a semi arid area of Rajasthan and its related risks to human health in the different groups of ages such as children, males, and females. We have found that most of the samples (n = 90) were influenced by anthropogenic activities. The background level of NO3- had been estimated as 7.2 mg/L using a probabilistic approach. About 93% of nitrate samples exceeded the background limit, while 28% of the samples were beyond the permissible limit of 45 mg/L as per the BIS limits. The results show that the oral exposure of nitrate was very high as compare to dermal contact. With regard to the non-carcinogenic health risk, the total Hazard Index (HITotal) values of groundwater nitrate were an average of 0.895 for males, 1.058 for females, and 1.214 for children. The nitrate health risk assessment shows that about 38%, 46%, and 49% of the samples constitute the non-carcinogenic health risk to males, females, and children, respectively. Children were found to be more prone to health risks due to the potential exposure to groundwater nitrate.

Arsenic enrichment and its natural background in groundwater at the proximity of active floodplains of Ganga River, northern India.

Arsenic contaminated groundwater is seen as one of the most critical routes of human exposure to geogenic pollutants. Recently around 40 million inhabitants of the world are living in the hazardous zone having groundwater As level >50 µg/L. As problem of groundwater in Bhagirathi-Ganga deltaic plain is well-known for over the last three decades. Hydrogeochemical analytical data related to the As concentration had been analysed to identify the As sources in groundwater of the active floodplains of the Ganga basin in Northern India. The natural background level of As was also estimated using Grubb's test and cumulative probability plots. The natural background level is a crucial parameter for identifying and quantifying groundwater pollution and assessing measures to control pollution. The anthropogenic addition of As in groundwater was separated by the estimated inflection point. The results show that the highest As concentration, which is 8-times more than the permissible limit, is observed at Gyantoli village in Begusarai district in Bihar state. Groundwater is alkaline with a high concentration of HCO3- as compared to other chemical parameters. Further, it indicates the dominance of carbonate weathering and relatively high pH values (range: 8.00-9.00) helps to release As in groundwater. The reducing environment of the aquifer system becomes oxic at the shallow depth due to comparatively shallow groundwater level, and impressive water level fluctuation resulting in vertical mixing of anthropogenic As contaminants.

Trace element concentration in groundwater of Pesarlanka Island, Krishna Delta, India.

There is a growing concern over the potential accumulation of trace element concentration in groundwater of coastal aquifer owing seawater encroachment in the last several decades. A total of 29 groundwater samples collected from Pesarlanka Island, Krishna delta, Andhra Pradesh, India were analyzed for 13 trace elements (B, V, Mn, Fe, Ni, Co, Cu, Zn, As, Sr, Cd, Ba, and Pb) using inductively coupled plasma mass spectrometry. The results reveal that B, Fe, Ni, As, Sr, and Pb vary from 11.22 to 710.2, 1.25 to 684.6, 0.02 to 37.33, 27.8 to 282.3, 164.1 to 7,009, and 1.97 to 164.4 microg/l, respectively. Ba, Cd, Co, Cu, Ni, V, and Zn are almost within permissible limits for drinking water, but As, Fe, Mn, Pb, B, and Sr are above the permissible limit. The toxic element Pb is 1.64 times more than the maximum permissible limits of drinking water. The minimum value of As is also 2.78 times more, whereas the maximum is 28.2 times the permissible limit. The spatial distributions of alkaline earths (Sr, Ba), transition metals (V, Co, Ni, Fe), metallic elements (Cu, Pb), and (As) were found in considerable variation in the entire Island. Good cross-correlations were found between As, B, Co, and Sr with total dissolved solids and among other trace elements such as B, As, Co, and Sr. The variability observed within the groundwater samples is closely connected to the sea spray input; hence, it is primarily a consequence of geographical and meteorological factors, such as distance from the ocean and time of year. The trace element levels, in particular those of heavy metals, are very low, suggesting an origin from natural sources rather than from anthropogenic contamination. A few trace elements (Sr and B) are found as sensitive parameters responding to changes in fresh to saline groundwater environment. The highly elevated trace elements in this area which may be attributed to marine sediments or death and decay of plants are presented in this paper.

Assessment of hydrochemical backgrounds and threshold values of groundwater in a part of desert area, Rajasthan, India.

Natural background levels (NBLs) and threshold values (TVs) are crucial parameters for identification and the quantification of groundwater pollution, and the evaluation of pollution control measures. The cumulative probability distribution technique was used for the evaluation of NBLs for 36 samples collected during two climate conditions in the part of the desert area from Rajasthan, India. The NBLs for Na+, Cl-, SO42-, HCO3-, NO3- and F- ions were assessed and compared with the natural and anthropogenic processes. The TVs were also calculated for Na+, Cl-, SO42-, HCO3-, NO3- and F- ions, and compared with the drinking limits of the Bureau of Indian Standards. Additionally, the pollution percentage (%) at the individual well was estimated and identified the polluted zones. Results indicate that most of the polluted areas were situated in the southern part, which was influenced by the natural and anthropogenic factors. The sodium concentrations above the TVs, in indicating the saline nature of water. Chloride threshold value above the drinking water limit was mainly observed in the dry season, related to intensive evaporation and industrial waste, which leads to groundwater quality degradation. The NO3- concentration (∼56% samples) above the TVs indicates extensive use of nitrate fertilizers and sewage effluent. The values of total dissolved solids (TDS) shows the suspicious scenario as about 84% of the samples in the dry period and about 89% in the wet season exceeding the drinking limit. Assessment of background concentrations and threshold values on regional and local scale assigns the basis for the identification of groundwater pollution, and helpful for better water quality guidelines to protecting of water resources.

Evaluation of groundwater resources in a tiny Andrott Island, Union Territory of Lakshadweep, India.

Lakshadweep is a group of 36 coral islands scattered in the Arabian Sea off the western coast of India. On such small tiny islands, groundwater is the only source of fresh water for the islanders. Due to the growing population on these islands, demand for fresh water is also increasing and on the other side the peculiar hydrologic, geologic and geomorphic features restrict the availability of groundwater. Therefore, a proper understanding of the groundwater condition is important in order to meet this increasing demand and also to formulate future development and management strategies. Detailed hydrogeological, geophysical and hydrochemical studies have been carried out to identify potential fresh groundwater resources and quantify vulnerable parts of Andrott Island, Union Territory of Lakshadweep. Systematic collection and analysis of hydrological, geophysical and hydrochemical data reveal that fresh groundwater is only available between 2.5 to 5.0 m depths and provide an early sign of deterioration in groundwater quality in the peripheral parts of eastern and western coasts of this island. It suggests immediate measures for arresting the deterioration in groundwater quality as well as augmentation for restoration of aquifer in some parts of the island.

Risk factors of diarrhoea among flood victims: a controlled epidemiological study.

The concept and practice of 'disaster preparedness and response', instead of traditional casualty relief, is relatively new. Vulnerability analysis and health risks assessment of disaster prone communities are important prerequisites of meaningful preparedness and effective response against any calamity. In this community based study, the risk of diarrhoeal disease and its related epidemiological factors were analysed by collecting data from two selected flood prone block of Midnapur district of West Bengal. The information was compared with that of another population living in two non-flood prone blocks of the same district. The study showed that diarrhoeal disease was the commonest morbidity in flood prone population. Some behaviours, like use of pond water for utensil wash and kitchen purpose, hand washing after defecation without soap, improper hand washing before eating, open field defecation, storage of drinking water in wide mouth vessels etc. were found to be associated with high attack rate of diarrhoea, in both study and control population during flood season compared to pre-flood season. Attack rates were also significantly higher in flood prone population than that of population in non-flood prone area during the same season. Necessity of both community education for proper water use behaviour and personal hygiene along with ensuring safe water and sanitation facilities of flood affected communities were emphasized.