Fluoride exposure through consumption of drinking water was studied in a heavily industrialised area and suitable measures were suggested to control the fluorosis risk to residents. Groundwater quality conforms to World Health Organization (WHO) criterion for drinking except for fluoride and is also suitable for irrigation. Fluoride concentration ranges from 0.1 to 4.4 mg/l and 39% of the total samples measured were found to be contaminated as per WHO limits (1.5 mg/l). The fluoride intake through drinking water was calculated to be 0.10 mg/kg/d for infants, 0.09 mg/kg/d for children and 0.05 mg/kg/d for adults with a corresponding exposure dose exceeding 2.1, 1.9 and 1.1 times for infants, children and adults, respectively, compared to the minimum risk value of 0.05 mg/kg/d. The fluorosis risk map indicates that with a few exceptions of some western and northwestern parts, the entire study area is prone to fluorosis and the highest being in the south central part. The fluoride exposure dose suggests the risk of mottled enamel among residents if untreated groundwater is provided for drinking for a long time. Considering the hydrogeological setup of this region, various amelioration methods to help mitigate the ill effects of high fluoride were evaluated and better nutrition containing calcium and vitamin C was found to be the most effective and viable option.

Sustainable groundwater management of an extreme climatic region is very important from both social and economic point of view. This study attempts to delineate the groundwater potential zones of Sonepur district, Odisha, which falls under an extreme climatic region, using remote sensing, geographical information system and Saaty’s analytical hierarchy process (AHP). Different ancillary data, multiple data sets obtained from LANDSAT 8 OLI and ASTER Level-1T were used in conjunction with Cartosat-1 imagery to study the detailed physical attributes of the study area and to prepare the groundwater prospect map using a weighted overlay method in ArcGIS 10.4 software. The AHP technique was used for determining the weights of each layer. From the groundwater prospect map, it was found that 52% of the area belongs to the moderate groundwater prospect zone followed by good to very good, very good to excellent (32%) and poor (16%) groundwater prospect zones. Statistical analysis of the number of existing wells in each of these water potential zones and their water level was used to verify the accuracy of the water potentiality estimated in this study. The groundwater potentiality map prepared as a part of this study would serve as an important tool for identifying suitable zones for rainwater harvesting and also for managing groundwater abstraction for a safe and sustainable water supply.

This paper elaborates the hydrochemical and environmental isotope ($\delta^{2}$H and $\delta^{18}$O) inferences obtained from Uddanam region, Andhra Pradesh, India. Groundwater samples collected during pre-monsoon (June 2019) showed that the quality is fresh (EC < 1539 $\mu$S/cm) and contaminants like fluoride (<1.6 mg/L) and nitrate (<49 mg/L) are present within permissible limits. The composite water quality indices for drinking (DWQI: 14.1–92.5) and irrigation (IWQI: 2.8–20.2) are found to be satisfactory. The major water types are found to be Ca–Na–HCO$_{3}$, Na–Ca–HCO$_{3}$, Na–Mg–HCO$_{3}$–Cl, Ca–Mg–HCO$_{3}$–Cl and Na–HCO$_{3}$. Three geochemical pathways are found signifying evaporite dissolution, contribution of silicate mineral weathering and base-exchange process, which is supported by estimated chloro-alkaline indices (CAI-1: −4.3 to −0.2, CAI-2: −1.03 to −0.08). Trace metal data clearly suggest that groundwater is free from any metal pollution. Dissolved silica (SiO$_{2}$) levels range from 34 to 131 mg/L and do not show any particular spatial trend. Isotope data infer that groundwater is recharged by rainwater after undergoing evaporation ($\delta^{18}$O: −6.0 per thousand), which matches with that of the combined isotope signature ($\delta^{18}$O: −5.5 per thousand) of SW and NE monsoon rainfall. $\delta^{18}$O–TDS correlations and hydrochemical facies evolution (HFE) diagram do not infer any seawater intrusion into these coastal aquifers.

$\bf{Highlights}$

$\bullet$ The composite water quality indices infer good to excellent category for drinking and agriculture.

$\bullet$ Mineral weathering, evaporite dissolution and base-exchange reactions are the main geochemical processes.

$\bullet$ Dissolved silica occurrence in groundwater is sporadic.

$\bullet$ Isotope indicators show the signature of both SW and NE monsoons recharge to groundwater.

$\bullet$ Observed brackishness in groundwater is due to water – rock interaction and not due to sea water intrusion.