Saltwater degrades large areas by killing less salt-tolerant species and leaving behind “ghost forests,” or wetland areas with only standing dead trees. Over time, saltwater intrusion along with rising sea levels and less rain converts these diverse wetland ecosystems to grass marshes and eventually to open saltwater. What is Saltwater Intrusion?
Saltwater intrusion occurs when salty H2O is drawn into freshwater aquifers affecting multiple wells in an aquifer, degrading water quality, making it unacceptable for drinking H2O & farming that’s made worse by higher temperatures & lack of rainfall dropping the H2O table inland below the ocean.
Water is always moving downwards until it finds its way until it gets to the sea. The same happens with groundwater. In coastal areas, where fresh groundwater from inland meets saline groundwater an interesting dynamic occurs. As salt water is slightly denser than freshwater, it intrudes into aquifers, forming a saline wedge below the freshwater.
What is Saltwater Intrusion
Saltwater intrusion is the movement of saline water into freshwater aquifers, which can lead to groundwater quality degradation, including drinking water sources, and other consequences. Saltwater intrusion can naturally occur in aquifers close to the coast, creating the hydraulic connection between groundwater and the sea.
Because saline water has a higher mineral content than freshwater, it is denser and has higher water pressure. As a result of water science, saltwater can push inland beneath the freshwater.
Under natural conditions, the seaward movement of freshwater keeps saltwater from encroaching on freshwater coastal aquifers. This interface between freshwater and saltwater is maintained near the coast or far below the land surface. The interface actually is a large spread-out area zone where freshwater and saltwater mix. The zone is referred to as the zone of dispersion or the zone of transition.
Groundwater pumping can reduce freshwater flow toward coastal areas and cause saltwater to be drawn toward the freshwater zones of the aquifer. Saltwater intrusion decreases freshwater storage in the aquifers, and, in extreme cases, can result in the abandonment of wells.
One part of the U.S. that has dealt with saltwater intrusion is Florida. In Florida, saltwater has intruded into groundwater supplies through different compounding ways. For example, saltwater has encroached into aquifers because fresh groundwater levels have decreased relative to sea level, allowing higher gradient water to flow toward the freshwater.
Also, leaking saltwater inland canals, leakage between aquifers, or even upwelling of saltwater from depth also have impacted freshwater aquifers. Water managers in Florida are using information from local, State, Tribal, and Federal saltwater intrusion monitoring networks, such as from the USGS, to prevent and reverse saltwater intrusion.
The salinity barrier between fresh groundwater and saltwater is referred to as the freshwater/saltwater interface. Fresh groundwater discharging to the coast prevents the landward encroachment of saltwater.
If too much freshwater is pumped from the aquifer system, then saltwater can migrate landward by a process referred to as “saltwater intrusion.” If a pumping well is close to the landward migrating freshwater/saltwater interface, saltwater could enter the well and contaminate the water supply, too.
USGS Water Intrusion Project
Saltwater encroachment has occurred to some level in many of the coastal aquifers located in the United States on the east coast.
Since saltwater cannot be used like a freshwater drinking system to irrigate crops or be consumed by people, saltwater intrusion can be a very serious problem for coastal communities that rely on fresh groundwater supplies for their livelihood.
The USGS studies show how excessive groundwater pumping, sea level rise, and other factors contribute to the saltwater encroachment of seawater intrusion polluting fresh groundwater system supplies.
This research study aids those who manage water supplies, allowing for better management strategies to protect coastal communities and their sources of water.
Saltwater intrusion occurs in many ways, including lateral encroachment from coastal waters and vertical movement of saltwater near community discharging wells.
The intrusion of saltwater caused by withdrawals of freshwater from the groundwater system can make the resource unsuitable for use. Thus, groundwater management plans should take into account potential changes in water quality that might occur in the near future directly because of saltwater intrusion.
Further, saltwater intrusion may cause agriculture to become unsuitable, enabling agriculture farmers to switch over to AQC as an alternative means of growing their typical crops. This could be a positive aspect of AQC. AQC is Alternative agriculture that is defined as production systems that do not use conventional methods. However, developing and adapting are key and of paramount importance in combating climate change impacts.
- Maintain and Restore Wetlands.
- Maintain Water Quality and Availability.
- Preserve Coastal Land and Development.
- Preserve Habitat.
- Use “Hard” Shoreline Maintenance.
- Use “Soft” Shoreline Maintenance.
The movement of saltwater into freshwater aquifers can harm groundwater quality in a variety of places with drought, especially with ongoing drought salinity. Seawater Intrusion or Saltwater encroachment is most common in coastal regions, where the fresh drinking water is displaced by the inland movement of saltwater from the ocean.
But it can also occur inland, far away from an ocean, as freshwater is pumped out from underground reservoirs and the salt-laden water from surrounding saline layers of the earth flow in through the science of seawater intrusion like in California or Florida.
Drought from Climate change can increase saltwater encroachment along coastal regions, particularly as the full sea level increases. The increased salinity of coastal freshwater can threaten the plant life and wildlife of coastal areas, destroy habitats such as wetlands, and threaten drinking water supplies.
Normally, along coastal regions, freshwater moves out to the sea from a bay in a river or stream. This outward flow creates a barrier that prevents seawater from moving inland. As well, the boundary between freshwater and saltwater (freshwater contains a lesser content of minerals than salt water and so will float on top) is normally to be near the coast rather than inland.
The ocean basins have a maximum volume that they can hold. As the amount of ocean full water increases, the ocean depth rises, causing the coastal ocean to push farther inland causing saltwater intrusion.
A rise in sea level can cause saltwater to move farther inland (seawater intrusion) in regions where the coastline is very near sea level in height, simply from the increased volume of water present. As well, the tendency of saltwater to penetrate underground freshwater reservoirs is increased.
What are the Functions of a Wetland?
The Functions of a Wetland are:
- Water purification
- Flood protection
- Shoreline stabilization
- Groundwater recharge
- Streamflow maintenance
- Provide habitat for fish & wildlife, including endangered species
- Trap sediments that contain contaminants & pollutants
- Help create biological productivity ……………………………………………………………………………………………………………….. Read more
Salt Water Soil
Most of the cash crops that are grown in the Northeast are not salt or flood tolerant. Researchers say that farmers may be able to continue generating income farming the land impacted by saltwater intrusion by planting alternative crops.
There are a few strategies that can improve soil health and lessen the effects of saltwater intrusion in the short term. However, these are not long-term answers. Farmers can remove excess salt from the soil through irrigation.
- Natural rainfall events will also help with this process.
- Farmers can also add gypsum to decrease excess salt in the
- Using compost and manure products with low salt levels. Cover crops, which help salt leach down through the soil by increasing the flow of water, can also be grown on affected fields for one season.
Adding Gypsum (calcium sulfate (CaSO4)) to the soil. Gypsum removes sodium by the interaction between the sulfate ions and sodium. The negatively charged sodium ions attract with the positively charged sodium ions, forming sodium sulfate, which is very highly leachable from the soil.
Conclusion
Saltwater intrusion occurs when salty H2O is drawn into freshwater aquifers affecting multiple wells in an aquifer, degrading water quality, making it unacceptable for drinking H2O & farming that’s made worse by higher temperatures & lack of rainfall dropping the H2O table inland below the ocean.
Water is always moving downwards until it finds its way until it gets to the sea. The same happens with groundwater. In coastal areas, where fresh groundwater from inland meets saline groundwater an interesting dynamic occurs. As salt water is slightly denser than freshwater, it intrudes into aquifers, forming a saline wedge below the freshwater.
Water availability is the quantity of water that can be used for human purposes without significant harm to ecosystems or other users. Consideration is given to demands from human and ecosystem needs, equitable apportionment of water among uses, and indicators of stress to the water resource .…………………………………………………………………… Read more
Reference:
USGA-Saltwater Intrusion
