What is "fossil water"

aquifer \aquifer\ n. 1. an underground bed or layer yielding ground water for wells and springs etc.; as, the Oglala aquifer. The water contained in an aquifer may be of great age, and in such cases is sometimes called

fossil water.

n. Water that has remained in an aquifer for a long timespan, usually thousands or millions of years.

“Fossil water” or paleowater is a somewhat broadly-used term to describe water that has been contained in some undisturbed space, usually groundwater in an aquifer, for millennia or longer. Fossil water could also describe ancient water on other planets, or water sealed in subglacial lakes such as Antarctica’s Lake Vostok. “Fossil groundwater” can be defined as “water that infiltrated usually millennia ago and often under climatic conditions different from the present, and that has been stored underground since that time.”

Determining the time since water infiltrated usually involves analyzing isotopic signatures. Determining “fossil” status—whether or not that particular water has occupied that particular space since the distant past—involves modeling the flow, recharge, and losses of aquifers, which can involve significant uncertainty. Some aquifers are hundreds of meters deep and underlie vast areas of land. Research techniques in the field are developing quickly and the scientific knowledge base is growing. In the cases of many aquifers, research is lacking or disputed as to the age of the water and the behavior of the water inside the aquifer.