Tirumalesh Keesari

Geochemical characterization of groundwater from an arid region in India

A study on the geochemical processes in arid region of western India (Kachchh district) was carried out using major, minor, trace metal data and isotopic composition (δ2H, δ18O) of groundwaters. Results indicate that the distribution of chemical species in groundwater of this district is controlled by leaching of marine sediments, dissolution of salts in root zone and incongruent dissolution of carbonate minerals. Common inorganic contaminants such as fluoride, nitrate and phosphate are within drinking water permissible limits. However, most of the samples analyzed contain total dissolved salts more than desirable limits and fall in doubtful to unsuitable category with regard to irrigational purpose. Trace metal data indicates no contamination from toxic elements such as arsenic and lead. An increased salt content is observed in groundwater at shallower depths indicating mixing with surface water sources. The chemical characteristics of the groundwater have found to be strongly dependent on the local lithological composition. Environmental isotopic data indicates that the groundwater is of meteoric origin and has undergone limited modification before its recharge. The processes responsible for observed brackishness are identified using chemical and isotope indicators, which are in agreement with subsurface lithology and hydrochemistry. These data though represent hydrochemical scenario of 2001 can still be used for understanding the long-term fluctuations in water chemistry and would be quite useful for the planners in validating groundwater quality models.

Assessment of groundwater chemistry in layered coastal aquifers using multivariate statistical analysis

This study presents statistical analysis of hydrogeochemical data of the groundwater samples collected from the layered formations of the Cretaceous, Tertiary (Lower Cuddalore and Upper Cuddalore) and Quaternary in Pondicherry region, South India. It focuses on the sources, controls and geochemical processes occurring in these formations. The results obtained from statistical analysis of 11 important hydrochemical parameters indicate dissimilar elemental correlations among aquifers. Quaternary aquifer exhibit good correlations among ion pairs Ca+–Cl− and Na+–Cl− indicating source controls like salts from unsaturated zone, fertilizers, industrial wastes and also processes like ion exchange. Upper and lower Tertiary aquifers have good correlations among ions as Ca2+–Mg2+–Na+–K+–Cl−–HCO32−—H4SiO4 indicating dominant role of silicate rock weathering processes, while Cretaceous formation show high correlations among Ca+–Mg2+–SO42−–HCO3− indicating carbonate and sulphate mineral contribution. High positive ion correlations among Na+–K+–Cl− observed in Cretaceous formation reflects contribution from marine sources. The study has also brought out the three major processes active in theses aquifers like parental, anthropogenic and mixing. The spatial distribution of the factor score for individual groundwater samples reveals the sources of the constituents that are in good agreement with those deduced from the geological and hydrogeological evidences. A conceptual geochemical model is developed to improve the understanding of this complex multi-layered aquifer system that would help the water authorities to plan for judicious exploitation of groundwater resources management without significantly hampering the groundwater quality.

Tracer-based estimation of temporal variation of water sources: an insight from supra- and subglacial environments

ABSTRACT The temporal variations in electrical conductivity and the stable isotopes of water, δD and δ18O, were examined at Chhota Shigri Glacier, India, to understand water sources and flow paths to discharge. Discharge is highly influenced by supraglacially derived meltwater during peak ablation, and subglacial meltwaters are more prominent at the end of the melt season. The slope of the best fit linear regression line for δD versus δ18O, for both supraglacial and runoff water, is lower than that for precipitation (snow and rain) and surface ice, indicating strong isotopic fractionation associated with the melting processes. The slope of the local meteoric water line (LMWL) is close to that of the global meteoric water line (GMWL), reflecting that the moisture source is predominantly oceanic. The d-excess variation in rainwater confirms that the southwest monsoon is the main contributor during summer while the remainder including winter is mostly influenced by westerlies.

Quality of water resources in Kullu Valley in Himachal Himalayas, India: perspective and prognosis

The water quality in mountain regions of Himalaya is considered to be good and quantity adequate. However, recent reports suggest that urbanisation and population growth have been tremendous, which are impacting the land use/cover changes and also endangering the water resources both in quality and quantity. This paper elaborates the systematic investigation carried out on different attributes impacting the drinking water resources in Kullu valley. Two approaches were employed in this study: (1) ex-ante approach involving field survey and secondary data analysis from ancillary sources and (2) hydrochemical approach for the measurement of water quality parameters from springs. Results from ex-ante approach infer rise in population of about 15% during 2001–2011, which led to a significant change in land use pattern, microclimate and also increased water demand. Hydrochemistry of the water samples in the study area has indicated that the current status of spring waters is satisfactory for drinking purposes with a few incidences of high NO3− which is mostly attributed to contamination from sewage, while F−, Cl− and TDS contamination is mainly confined to hot springs. From both ex-ante approach and primary hydrochemical data it can be inferred that springs need to be restored in terms of both quantity and quality. Hydrochemical interpretation suggests two main groups of samples: (1) low TDS and Ca–Mg–Cl–HCO3 type, which are mainly recharging waters with very less interaction with the aquifer material and (ii) moderate TDS and Mg–Ca–Cl, Ca–Na–HCO3, Na–Ca–Cl–SO4 and Ca–Mg–HCO3 and have undergone water–rock interaction. Based on the inferences obtained from the Piper’s, Chadha’s and Durov’s classification no evidence of hot springs contaminating or contributing to other cold springs and shallow groundwater (hand pump) is found. The study concludes that the water resources are vulnerable to anthropogenic interventions and needs treatment prior to drinking. Periodic monitoring of water quality and adopting proper treatment procedures are essential for supplying safe and sustainable water to the community in the Kullu valley, Himachal Pradesh.

Occurrence of Uranium in Groundwater Along the Lithological Contacts in Central Tamilnadu, India: An Isotope Hydrogeochemical Perspective

Groundwater contributes to the highest exposure level of naturally occurring uranium (U) to biosphere, and hence, the source and concentration of uranium in groundwater needs to be monitored periodically. In the present study, groundwaters from different lithologic locations were collected and measured for uranium concentration and major ions in order to establish any possible link with the lithology on the uranium distribution in central parts of Tamil Nadu, South India. About 11% of the samples contain U in excess of the permissible limit of WHO (Guidelines for drinking-water quality, WHO, Geneva, 2011), and the contamination was limited to mostly hard rock terrain, which is granitic in nature. The correlations among U, major ions, and environmental isotopes were studied to understand the mechanism governing uranium dissolution and transport in groundwater of this region. Observations lead us to infer that the older water with near-neutral pH and oxidizing condition contains higher dissolved U compared with relatively young groundwater. The results also reflect the possible health risk to the local population through long-term consumption of uranium-containing groundwater without any pretreatment.