Groundwater age dating using tritium
The concentrations of all substances moving with water through the unsaturated zone and beneath the water table are affected, to some extent, by transport and chemical processes, including dispersion, mixing, degradation, and sorption.
In Alaska, the presence of most manmade substances in a ground-water sample indicates some recent recharge (within about the last 50 years).
Ground water moves slowly from its point of recharge to its point of use or discharge.
This water starts as rain and melting snow that soak into the ground as recharge.
Groundwater age distribution characteristics indicated that groundwater flows from the mountain area to the basin area, and that the oldest groundwater in each high-age zone flows toward the depression cones.
Wells that have long screened intervals may produce a mixture of water from several parts of an aquifer system that have different recharge areas and flow paths, which would yield different ground-water ages.Ground-water resources provide about one-third of the water used for domestic, commercial and industrial purposes in the Anchorage metropolitan area and are the sole sources of water for industries and residents outside Anchorage.