Abstract:
Stable isotopes of H and O are the integral parts of water molecule and serve as
ideal tracers to understand the recharge processes in groundwater. Hence, a study has been
conducted in hard rock aquifers of Madurai District of Tamilnadu to identify the recharge
processes using stable isotopes. A total of 54 groundwater samples were collected representing
the entire district from various lithounits during post monsoon. Samples were analysed for pH,
EC, Ca2+, Mg2+, Na+, K+, Cl− HCO3
−, SO42−, PO43−, H4SiO4, F−, δ18O and δD. Cl− and
HCO3
− were the dominant ions in groundwater samples. Average values of Cl− and HCO3
−
ranged from 247 and 244 mg/L in fissile hornblende biotite gneiss, 262 and 268 mg/L in
Charnockite, 75 and 185 mg/L in quartzite, 323 and 305 mg/L in granite, 524 and 253 mg/L in
floodplain alluvium rock types. Geochemical signatures of groundwater were used to identify
the chemical processes that control hydrogeochemistry. Interpretation of δ18O and δD indicates
recharge from the meteoric water in charnockite, quartzite, granite and some samples of
fissile hornblende biotite gneiss. It is also inferred that recharge take place from evaporated
water in floodplain alluvium and fissile hornblende biotite gneiss.
