Saltwater Intrusion: By 2100, Saline Water in 77% of Global Aquifers
By 2100, over three-quarters (77%) of coastal aquifers will face saltwater intrusion. The primary drivers behind this increase are a combination of rising sea levels and reduced groundwater recharge. While rising sea levels exert greater pressure from seawater onto coastal freshwater, diminished recharge weakens the resistance of freshwater reserves.
This finding comes from a study on future vulnerability to saltwater intrusion published in Geophysical Research Letters. The research was led by the Jet Propulsion Laboratory at the California Institute of Technology (NASA) in Pasadena, California.
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Three Scenarios of Saltwater Intrusion
The authors analyzed three scenarios, each considering some or all contributing factors to saltwater intrusion, highlighting regions where the phenomenon would be most pronounced:
- Scenario 1: Changes in Aquifer Recharge (Excluding Sea Level Rise)
Significant saltwater intrusion is projected in 45% of coastal areas, particularly in arid regions like the Arabian Peninsula and Western Australia. Italy presents a mixed situation in this scenario: central regions see a retreat of the saltwater wedge, while the rest of the peninsula experiences limited increases. - Scenario 2: Sea Level Rise (Excluding Recharge Changes)
Rising sea levels alone cause saltwater intrusion in 82% of coastal areas, especially in low-lying regions like Southeast Asia. The overall intrusion extent is smaller than in Scenario 1. For Italy, this is the most favorable scenario, with only limited increases in saltwater intrusion across most regions. - Scenario 3: Combined Effects of Sea Level Rise and Recharge Changes
This scenario results in the most widespread saltwater intrusion, affecting 77% of coastal areas and pushing the saltwater front an average of 210 meters inland. In Italy, some regions still experience a retreat of the saltwater wedge, but areas with severe intrusion emerge, particularly in Sicily and specific locations along the Adriatic coast.
“Depending on where you are and which factor dominates, the implications for managing the phenomenon could vary,” said Kyra Adams of JPL, the study’s lead author.