Saltwater gets into groundwater primarily through a process called saltwater intrusion.
Saltwater Intrusion Explained
Here’s how saltwater intrusion occurs and contaminates freshwater aquifers:
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Infiltration: Saltwater can directly infiltrate (seep) into freshwater aquifers. This happens when saltwater, from the ocean or other sources, moves through the soil and porous rock layers into underground freshwater reservoirs.
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Rising Sea Levels: As sea levels rise, saltwater can move further inland. High tides and storm surges can push saltwater over low-lying coastal areas. This leads to more saltwater infiltration into the ground and groundwater.
- Example: During a major storm, seawater may flood coastal regions, and some of this water will percolate into the ground, eventually reaching groundwater supplies.
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Groundwater Table Issues: Saltwater intrusion can raise the groundwater table below the soil surface. This means that the area where the groundwater is located becomes partially or fully filled with saltwater instead of freshwater.
- Impact: The freshwater is displaced by saltwater and can cause wells to pump saltwater.
Summary of How Saltwater Enters Groundwater
| Mechanism | Description |
|---|---|
| Infiltration | Saltwater seeps directly into freshwater aquifers through the ground. |
| Sea Level Rise | Rising sea levels push saltwater inland, leading to increased infiltration. |
| Storm Surges and Tides | Storm surges and high tides overtop low-lying areas, forcing saltwater into the ground. |
Practical Insights
- Coastal Areas: Coastal regions are particularly vulnerable to saltwater intrusion due to their proximity to the ocean.
- Over-pumping: Excessive extraction of groundwater in coastal areas can lower water pressure and allow saltwater to move inland more easily.
- Environmental Impact: Saltwater contamination of groundwater can render the water undrinkable, harm agriculture, and disrupt ecosystems.
Solutions and Mitigation
- Managed Groundwater Extraction: Controlled pumping of groundwater can help maintain water pressure and prevent saltwater from moving inland.
- Barriers: Creating physical or hydraulic barriers can help to prevent or reduce saltwater infiltration.
- Water Conservation: Reducing overall water usage can alleviate pressure on freshwater aquifers.
