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Around 9000 inhabitants in the Panda River basin, Sonbhadhra District, Uttar Pradesh, India, are vulnerable to a “silent” dental and skeletal fluorosis from groundwater consumption. The fluoride source and seasonal groundwater quality variation were studied by collecting 65 groundwater samples in the Upper Panda River basin. Major rock types are phyllites and granite gneissic rocks. Fluoride concentrations are in the range 0.4–5.6 mg/L in the pre-monsoon season and 0.1–6.7 mg/L in the post-monsoon season. Fluor-apatite and biotite mica in the granite gneissic rock were identified as the main provenance of fluoride in the groundwater through water–rock interactions. Due to precipitation of calcium, soils become alkaline with high contents of sodium; these conditions allow fluoride to accumulate in water. According to risk index calculations, the fluoride-affected villages were shown to fall in the fluoride risk zone (with a risk index of around 1.7). On the basis of mineral stability diagrams, groundwater from the weathered and fractured aquifers appears to be stable within the kaolinite field, suggesting weathering of silicate minerals. The groundwater is chemically potable and suitable for domestic and agricultural purposes, except for a few wells in the southern region that are contaminated with high amounts of fluoride. Editor D. Koutsoyiannis Citation Raju, N.J., Dey, S., Gossel, W., and Wycisk, P., 2012. Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin, Sonbhadra District, Uttar Pradesh, India. Hydrological Sciences Journal, 57 (7), 1433–1452. [ABSTRACT FROM AUTHOR]

Correlations and multiple linear regressions were used to develop models relating well water chemical quality parameters to a set of independent chemical variables in post- and pre-monsoon seasons in the upper Gunjanaeru River basin, Cuddapah district, Andhra Pradesh, South India. The correlation between the specific electrical conductance (SEC) and other parameters except potassium (K+) is significantly positive, whereas Ca2+ + Mg2+/Na+ + K+ is significantly negative for both post- and pre-monsoon seasons. In predicting SEC for both post- and pre-monsoon, the independent variables, viz. HCO3-, SO42- and Cl- in the model had a significant effect (from 't' test for partial regression coefficient at the 5% level of probability). The multiple R² values 0.982 and 0.997 indicate that 98.2 and 99.7% of variability in the observed SEC could be ascribed to the combined effect of Na+, Cl-, Ca2+ + Mg2+, HCO3-, and SO42- for post- and pre-monsoon seasons, respectively. Out of the 98.2% variability in SEC due to the combined effect of Na+, Ca2+ + Mg2+, HCO3-, SO42- and Cl-; 44.8% is due to HCO3-, 44.4% is due to Cl-, 9% is due to SO42- and 2% each is due to Na+ and Ca2+ + Mg2+ for post-monsoon season. Whereas in the pre-monsoon season, 99.7% variability in SEC is due to the combined effect of Na+, Ca2+ + Mg2+, HCO3-, SO42- and Cl-; 38.8% is due to Cl-, 36.9% is due to HCO3-, 12% is due to Na+, 7% is due to SO42- and 3% is due to Ca2+ + Mg2+. This shows that HCO3-, Cl-, SO42- and Cl-, HCO3-, Na+, SO42- are the most significant independent variables in predicting SEC for post- and pre-monsoon seasons respectively. [ABSTRACT FROM AUTHOR]

• Godavari geothermal province is manifested with several geothermal waters with issuing surface temperature 30–55 °C and near neutral nature (pH: 6.5–7.3). • The investigation suggests a moderate enthalpy geothermal system. • The heat flow value observed in geothermal wells ranges from 83 to 388 mW/m2 which provide geothermal gradient range 22.5–105.5 °C/km in Manuguru area. • This research suggest that the Manuguru area can produce 3584 MW e using Organic Rankin Cycle (ORC). The Godavari geothermal field in India is one of the potential areas manifested by several geothermal waters and groundwaters. The geothermal waters of the area are near neutral (pH: 6.5–7.3) with surface temperature ranging from 30 to 55 °C while groundwaters are also near neutral (pH: 6.6–7.5) with surface temperature ranging from 24 to 28 °C. The hydrogeochemistry of the geothermal waters suggests that the geothermal waters show a Na-Ca-SO 4 -HCO 3 to a Ca-HCO 3 type and groundwaters are of the Ca-HCO 3 to Na-Ca-HCO 3 type while groundwaters and river waters are of the Ca-Na-SO 4 types. The geothermal waters of the study area are enriched in SO 4 2– and Cl–, due to the interaction with the pyrite-bearing Gondwana sediments and granitic gneiss basement rocks. Furthermore, enrichment of Ca2+, Mg2+ and an increased HCO 3 /Cl ratio in geothermal water is caused by the exchange and/or mixing process that takes place during water-rock interaction at an elevated temperature while ascending to the surface. This type of behavior of water is also observed during the water-rock interaction experiment at 100 °C. Studies on geothermal gas geochemistry suggest the deeper circulation of geothermal waters in the crust and high helium concentration as a thermal gas that can be utilized for commercial purposes. Estimated reservoir temperatures from quartz and Na-K-Ca geothermometry are in the range 110–195 °C. Therefore, the geothermal water of the study area is categorized as a moderate enthalpy geothermal system. Thermal logging in the borewell and depth range from 50 to 1000 m suggest that the geothermal gradient in the Manuguru area ranges from 22.5 to 105.5 °C/km and heat flow ranges from 83 to 388 mW/m2, which is higher than the regional condition. Therefore, 3584 MW e power can be produced by using the Organic Rankine Cycle (ORC) from the Manuguru geothermal area of Godavari valley. [ABSTRACT FROM AUTHOR]