In this context, extensive ...

In this context, extensive field investigations were carried out by my team and me, for over four decades in different parts of India under semi-arid and arid conditions, using radioactive (3H, 14C, 234U, 238U) and stable (2H, 18O) isotopes. Mean recharge in river basins has been estimated using tritium injection technique by tracing soil moisture movement. Regional groundwater residence time in the aquifer and flow velocity has been estimated by 14C (T1/2 = 5730 yr) ages of groundwater. Groundwater seepage loss has been assessed using seasonal variation of 18O/16O and 234U/238U isotopic ratio and 238U concentration in groundwater and river water, representing varying components of overland and subsurface flow. 2H/1H and 18O/16O ratios have been used for detailed insight into the groundwater recharge and contamination characteristics, flow regime, flow-pathways and mixing in groundwater system. Potentials of isotope techniques based on my own four decades of experience provided a direct insight into the water dynamics and distribution within hidden groundwater aquifers system, and proved to be very useful for groundwater management.