"Climate change may be creating a groundwater "time bomb" as the world's underground water systems catch up to the impacts of global warming.

Researchers for a study published Monday in the journal Nature Climate Change say more than half of the world’s groundwater systems — the largest source of usable freshwater in the world — could take more than 100 years to completely respond to current environmental changes from global warming.

Groundwater is replenished primarily by rainfall through a process known as recharge. Concurrently, water exits or discharges from groundwater sources into lakes, streams and oceans to maintain an overall balance.

When there is a change in recharge due to a lack of rainfall, for example, levels of groundwater drop until balance is restored. "

Pam Wright reports for the Weather Channel January 23, 2019. [2]