Integrated hydrochemical and ERT approach for seawater intrusion study in a coastal aquifer: a case study from Jafrabad Town, Gujarat State, India.

Hydrochemical and geophysical approach has been adopted to evaluate the seawater intrusion (SWI) in coastal aquifers of Jafrabad Town, Gujarat State, India. Electrical Resistivity Tomography (no. 9) was carried out with spread length of 160-400 m which provided penetration depth of about 23 to 76 m. Very low resistivity zone (0-3 Ω-m range) has been observed in the ERT profiles conducted in the study area. Parameters, namely, TDS, Na, and Cl, have been considered to examine the signature of SWI. The results obtained from ionic ratios, Piper plot, and Chaddha's diagram also confirm the influence of saline water within aquifer. The very low resistivity signature is correlated with the high TDS values in the nearby wells. SWI has been observed up to 9 km from the coast, and it is observed at a depth of 20-22 m in the existing limestone mines near the coast.

Impact assessment of on-site sanitation system on groundwater quality in alluvial settings: A case study from Lucknow city in North India.

The present case study has been undertaken to investigate the impact of on-site sanitation on groundwater quality in alluvial settings in Lucknow City in India. The groundwater samples have been collected in the areas of Lucknow City where the on-site sanitation systems have been implemented. The groundwater samples have been analyzed for the major physicochemical parameters and fecal coliform. The results of analysis reveal that none of the groundwater samples exceeded the Bureau of Indian Standards (BIS) limits for all the parameters. Fecal coliform was not found in majority of the samples including those samples which were very close to the septic tank. The study area has a thick alluvium cover as a top layer which acts as a natural barrier for groundwater contamination from the on-site sanitation system. The t test has been performed to assess the seasonal effect on groundwater quality. The statistical t test implies that there is a significant effect of season on groundwater quality in the study area.

Assessment of the impact of on-site sanitation systems on groundwater pollution in two diverse geological settings--a case study from India.

On-site sanitation has emerged as a preferred mode of sanitation in cities experiencing rapid urbanization due to the high cost involved in off-site sanitation which requires conventional sewerages. However, this practice has put severe stress on groundwater especially its quality. Under the above backdrop, a study has been undertaken to investigate the impact of on-site sanitation on quality of groundwater sources in two mega cities namely Indore and Kolkata which are situated in two different geological settings. The parameters for the studies are distance of groundwater source from place of sanitation, effect of summer and monsoon seasons, local hydro-geological conditions, and physico-chemical parameters. NO(3) and fecal coliform concentrations are considered as main indexes of pollution in water. Out of many conclusions which can be made from this studies, one major conclusion is about the influence of on-site sanitation on groundwater quality is minimal in Kolkata, whereas it is significant in Indore. This difference is due to the difference in hydrogeological parameters of these two cities, Kolkata being on alluvium quaternary and Indore being on Deccan trap of Cretaceous to Paleogene age.

Integrated hydrochemical and geophysical studies for assessment of groundwater pollution in basaltic settings in Central India.

The Pithampur Industrial sectors I, II, and III, located approximately, 45 km from Indore in Central India have emerged as one of the largest industrial clusters in the region. Various types of industries ranging from automobiles to chemicals and pharmaceuticals have been set up in the region since 1990. Most of the industries have effluent treatment plants (ETP) for treating wastewater before its disposal on land and/or in water body. The present study is an attempt to assess the groundwater quality in the watersheds surrounding these industrial sectors to develop the baseline groundwater quality in order to enable the policy makers to facilitate decisions on the development of industries in this region. The industries are located in two sub-watersheds, namely, Gambhir river sub-watershed and Chambal river sub-watershed. Geologically, the study area is located in the Deccan traps of Cretaceous to Paleocene age. The different basaltic flow units underlie clayey soils varying in thickness from 2-3 m. The aquifer is mostly of unconfined nature. Samples have been collected from a network of observation wells set up in the watersheds. The water quality analysis of the groundwater samples has been carried out six times during three hydrological cycles of 2004, 2005, and 2006. The results indicate that a few observation wells in the vicinity of the industrial clusters have very high TDS concentration and exceed the Bureau of Indian Standards (BIS) guideline for TDS concentration. The contamination of groundwater has been more severe in the Gambhir watershed as compared to the Chambal watershed. The presence of the impermeable clay layers has resulted in a slow migration of contaminants from the sources. The findings reveal that there is no significant groundwater contamination in the Pithampur industrial sectors except in the vicinity of the industrial clusters, which indicates that there is good environmental space available for the expansion of industrial units in the Pithampur industrial hub.

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.

Effect of on-site sanitation on groundwater contamination in basaltic environment--a case study from India.

On-site sanitation is increasingly adopted in urban cities in India. The adoption of on-site sanitation system puts the groundwater resources in the vicinity of the system at a greater risk. Microbial contaminants as well as chemical contaminants like Chloride and Nitrate are generated from human waste. These contaminants travel through the medium and ultimately get in contact with the groundwater. Hence, the groundwater sources are vulnerable to nitrate contamination near the on-site sanitation systems. The present study indicates significant Nitrate and Chloride contamination in samples collected close to on-site sanitation systems. The recommended limit set by the Bureau of Indian standards (BIS) limit of 45 mg/l for Nitrate concentration is also exceeded in few samples. The study indicates that Bacterial as well as Nitrate contamination is more in Monsoon as compared to Summer.

Assessment of pollution near landfill site in Nagpur, India by resistivity imaging and GPR.

Groundwater pollution in the vicinity of a landfill site in Nagpur, India is assessed with the help of resistivity imaging and GPR tools. The resistivity imaging survey indicates high conductive anomalies in the topsoil as well as the underlying fractured rocks. Significant reflections from the GPR records known as radargrams are extracted with the help of maximum peak module and Hilbert transform module in RADAN 6. These reflections can be attributed to presence of fractures, which are potential pathways for migration of the fluid. The geophysical findings are strengthened by the results of groundwater analysis from wells located close to the profile where resistivity and GPR survey have been carried out. The study has indicated the vulnerability of the unconfined aquifer underlying the predominantly clay layer.

Source apportionment of groundwater pollution around landfill site in Nagpur, India.

The present work attempts statistical analysis of groundwater quality near a Landfill site in Nagpur, India. The objective of the present work is to figure out the impact of different factors on the quality of groundwater in the study area. Statistical analysis of the data has been attempted by applying Factor Analysis concept. The analysis brings out the effect of five different factors governing the groundwater quality in the study area. Based on the contribution of the different parameters present in the extracted factors, the latter are linked to the geological setting, the leaching from the host rock, leachate of heavy metals from the landfill as well as the bacterial contamination from landfill site and other anthropogenic activities. The analysis brings out the vulnerability of the unconfined aquifer to contamination.