Groundwater is a major source for drinking and agricultural purposes to most of the population in Udupi district, southern India. The objective of the current study is to evaluate the spatial distribution of major ions and drinking water quality index in the study area. Groundwater samples (N = 100) were collected during pre-monsoon season. The collected samples were analyzed for major cations and anions. Based on electrical conductivity, 90 open wells were classified as fresh (<1500 µS/cm), four open wells as brackish (1500–3000 µS/cm) and six open wells as saline (>3000 µS/cm). The evaluation of drinking water quality index identified that seven groundwater samples are good, four are poor, two are very poor, three are considered to be unsuitable for drinking and 84 groundwater samples are excellent for drinking purposes. Human health risk assessment revealed that infants were more vulnerable to health risk than other age groups. The concentrations of nitrate in the two open wells were above the prescribed limit (>45) which could cause human health risk for all the age groups. Water management plan in the study area should prioritize to reduce the nitrate contamination in the study area.

Groundwater quality assessment is essential to understand land use impacts and implement water management plans. The present study aims to assess the impact of land use/land cover (LULC) on the groundwater table, and its quality in the tropical unconfined aquifers. Two hundred groundwater samples were collected from 100 sampling wells during monsoon and post-monsoon seasons. The drinking water quality index and irrigation quality indices were estimated based on the various parameters obtained from the laboratory analysis. Human health risk concerning nitrate contamination was evaluated based on the USEPA method. The land-use/land-cover map prepared using ArcGIS showed that the study area consists dominantly of croplands. Drinking water quality index results suggested that the groundwater samples were excellent to moderately suitable for drinking purposes. Only one sample was unsuitable for drinking. The different irrigation quality indices revealed various degrees of groundwater suitability for irrigation purposes. The spatial distribution of the corrosivity ratio suggests avoiding the metal pipe, for transportation of groundwater supply in the northern part of the study area. Fertilizers used in agriculture and soak pit leakages have contributed to high nitrate concentration in a few parts of the study area. Human health risk assessment showed that infants are vulnerable to non-carcinogenic health risks. The impact of the LULC assessment revealed that groundwater quality was moderately suitable for drinking in urban land. The study suggests implementing proper sewage treatment measures to avoid groundwater contamination. Overall, the findings are important in adopting site-specific, groundwater management strategies in the study area. Polluted and unpolluted areas demarcated in the study are beneficial for decision-makers to develop suitable groundwater management plans. The study recommends informed LULC development in the study area to improve groundwater quality and reduce human health risks.

Groundwater is a vital natural resource for drinking and irrigation purposes in India. Heavy metal contamination in groundwater is a global concern and leads to potential health risks to humans and the ecosystem. The aim of this study is to evaluate heavy metal contamination and human health risk in hard rock aquifers of southwest India. Groundwater samples were collected from open wells during the pre-monsoon and monsoon seasons. Heavy metal analysis was conducted using ICP-MS. Geostatistical interpolation technique was applied for spatial analysis. The results revealed that north-west region of the study area have a significant concentration of heavy metals in both the seasons due to intensive agricultural activity. Human health risk assessment in the study area revealed that children are more prone to health risks than adults and infants. Further, this study suspects moderate risk to the groundwater dependent ecosystem. Factor analysis indicates that heavy metals present in groundwater were derived from both geogenic and anthropogenic factors during both seasons. The study concludes that regular monitoring of groundwater is essential to control heavy metal contamination from anthropogenic activities. The heavy metal data obtained from this study can be a valuable database for decision makers to choose the areas of concern, for future water management plans.

The principal objective of this study is to assess the saltwater intrusion and hydrogeochemical processes that affect groundwater geochemistry in the coastal aquifers of southwestern India. Groundwater samples were collected seasonally and the physico-chemical parameters determined on-site. Major ions were determined in the laboratory. Hydrochemical diagrams, ionic ratios, and multivariate statistical analysis were adopted for understanding the groundwater chemistry. Gibbs plot identified that rock-water interaction and evaporation were the mechanisms regulating hydrogeochemistry. Ionic ratios have shown that coastal wells were contaminated with saltwater intrusion during the pre-monsoon season. Hierarchical cluster analysis classified the samples based on their quality; sample clusters with high NO3- were in densely populated areas, whereas sample clusters with moderate salt content in the coastal areas. Another cluster showed high concentrations of salts, typically the zones of saltwater intrusion. The study concludes that influence of seasons, geogenic and anthropogenic factors contribute to the heterogeneous chemistry of groundwater.

Spatio-temporal behaviour of dissolved organic carbon (DOC), inorganic carbon (DIC) and silica (DSi) along the salinity gradient of three south-west Indian monsoonal estuaries are presented. This study showed both conservative and non-conservative behaviour of DOC along the salinity gradient under varying physico-chemical conditions. The gross flux of DOC arriving at the estuary from the rivers was estimated as 0.9 x 109 g/yr for Sita-Swarna river, 4.2 x 109 g/yr for Sharavati river and 5.6 x 109 g/yr for Kali river. Similarly, the net fluxes of DOC estimated beyond the estuarine zone was 5.5 x 109 g/yr (Sita-Swarna), 8.0 x 109 g/yr (Sharavati) and 7.7 x 109 g/yr (Kali). This indicates that these estuaries are the sources of organic carbon to the ocean. The DIC linearly increased towards the higher salinity with net fluxes of 38 x 109 g/yr (Sita-Swarna), 75 x 109 g/yr (Sharavati) and 97 x 109 g/yr (Kali). The combined DIC flux of Sita-Swarna, Sharavati and Kali rivers is -8% of the total DIC fluxes received from the west flowing rivers of India, to the Arabian Sea. The DSi showed a biogenic removal of 80?85% in all the studied estuaries. From this study it is concluded that the west flowing river estuaries are net sources of DOC and DIC and net sink for DSi. Consideration of the role of west flowing rivers of peninsular India is important for the better understanding of the carbon dynamics in the river-estuary-ocean boundary.