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Abstract Deep groundwater is an important source of drinking water, and can be preferable to shallower groundwaters where they are polluted by surface-borne contaminants. Surface-borne contaminants are disproportionately common in ‘modern’ groundwaters that are made up of precipitation that fell since the ~1950s. Some local-scale studies have suggested that groundwater pumping can draw modern groundwater downward and potentially pollute deep aquifers, but the prevalence of such pumping-induced downwelling at continental scale is not known. Here we analyse thousands of US groundwater tritium measurements to show that modern groundwater tends to reach deeper depths in heavily pumped aquifer systems. These findings imply that groundwater pumping can draw mobile surface-borne pollutants to deeper depths than they would reach in the absence of pumping. We conclude that intensive groundwater pumping can draw recently recharged groundwater deeper into aquifer systems, potentially endangering deep groundwater quality.
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This content will become publicly available on May 28, 2026
Sustainability of Tapping Ancient Groundwater
Fossil groundwaters make up a substantial fraction of the Earth's fresh water and are being targeted for water supply wells at increasing rates. These groundwaters were recharged more than 12,000 years ago, often in climate conditions that were much different from those of today. Because of the long renewal times involved, fossil groundwaters have often been classified as nonrenewable. However, groundwater ages provide little insight into how water levels and fluxes will change as the result of pumping. The relationship between groundwater ages and these outcome-based metrics of renewability is not straightforward. Therefore, whether a groundwater is fossil or not may have little to do with its renewability. The hydraulic response of an aquifer system to pumping is not strongly related to groundwater age. The use of both modern and fossil groundwater can be unsustainable.
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- Award ID(s):
- 2120733
- PAR ID:
- 10614331
- Publisher / Repository:
- Annual Reviews
- Date Published:
- Journal Name:
- Annual Review of Environment and Resources
- ISSN:
- 1543-5938
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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