|Trevor Nace reports that the largest and most extensive study to date on Earth groundwater has revealed surprising results regarding modern groundwater recharge rates. Ancient (= deep) groundwater remains largely unknown and uncharacterized, limiting hydrogeologist understanding of recharge rates and cycle times.|
Groundwater is a vital component of practically every system on Earth and has been used extensively in modern times for irrigation, potable water, and industrial activity. Further understanding of the recharge time, or the time that groundwater takes to be replenished, allows hydrologists to identify imbalances in the underground system.
Hydrogeologists have identified modern (shallow and less than 50 years old) and ancient (= deep) groundwater and mapped the respective reserves throughout the world. Modern groundwater is most vulnerable to human activity and climate and must be understood to effectively manage fresh water supplies around the world...because it is shallow and relatively cheap to pump to the surface.
To get a sense of the overall distribution of fresh water around the world, the diagram provided offers valuable information. Ancient groundwater storage, at 21.97 million cubic kilometers, is by far the largest source of fresh water in the world. However, replenishment of ancient groundwater takes place over millions of years. We must effectively manage both surface water and modern groundwater in order to limit strain on ecosystems both human and non....but the older the groundwater, the higher the total dissolved solids (TDS) because it has traveled long distances picking up chlorides, iron and other elements along the way. It usually needs to be treated to remove such dissolved elements.