Recent advances in dating young groundwater: Chlorofluorocarbons, H-3/He-3 and Kr-85

Chlorofluorocarbons, H-3/He-3 and Kr-85 are tracers of atmospheric origin that can be used to date groundwater over periods from 0 to 40 years. In suitable aquifers, measured groundwater ages can be used to estimate groundwater flow paths, and vertical and horizontal flow velocities. In simple, piston flow systems they can be used to estimate groundwater recharge rates with an accuracy of 20% or less, better than can be achieved with traditional hydraulic-based methods. Groundwater dating methods have also been used to reconstruct past releases of contaminants to aquifers.