Salinity ingress is also known as a saltwater intrusion. It is a natural and human-induced phenomenon that occurs when saline or saltwater enters previously dominated freshwater environments within coastal areas. This gradual process is characterized by the encroachment of saltwater into various freshwater sources, including rivers, estuaries, groundwater reservoirs, and even surface water bodies like lakes and lagoons, which are typically associated with lower salinity levels.
This results in the gradual displacement of freshwater by saltwater, converting the pure sources of drinking water into brackish or saline and making the fertile agricultural lands unsuitable for cultivation. Furthermore, this process disrupts the biodiversity of coastal ecosystems, threatening the habitats of numerous species, impacting fisheries, and ultimately the ecological imbalances.
Salinity ingress stands as an emerging environmental issue that requires adaptive strategies to minimize its adverse effects on coastal communities, ecosystems, and the delicate equilibrium between saltwater and freshwater in these vulnerable regions.
Causes for Salinity Ingress
1. Rising Sea Levels
One of the most prominent contributors to salinity ingress is the rising sea level, a direct consequence of global climate change. As the Earth's temperature increases, polar ice caps and glaciers melt, causing sea levels to rise. This elevated sea level has a profound impact on coastal areas, allowing saltwater to push further inland. This process is especially concerning in low-lying coastal regions, where even small increases in sea level can result in significant salinity intrusion.
2. Over- Extraction of Groundwater
Coastal communities often rely on groundwater as a primary source of freshwater. However, excessive extraction of groundwater for agriculture, industrial processes, and domestic use can lead to a drop in the water table. When the water table decreases, it creates a hydraulic gradient that draws saline water from the nearby sea into the freshwater aquifers. This intrusion of saltwater can contaminate groundwater, making it unsuitable for consumption and agricultural ecology.
3. Climate-Induced Extreme Weather Events
Extreme weather events, such as hurricanes, typhoons, and storm surges, can exacerbate salinity ingress. These events, driven by climate change, can result in the inundation of coastal areas with seawater. The force of the storm surge can push saltwater deep into coastal regions, affecting both surface water sources and groundwater reservoirs. Even after the event subsides, the lingering saltwater can continue to impact the affected areas.
4. Land Use Changes and Deforestation
Human activities, including deforestation and changes in land use, can alter natural drainage patterns and exacerbate salinity ingress. Forests and wetlands play a vital role in regulating water flow and preventing saltwater intrusion. When these natural buffers are removed or disrupted, it becomes easier for saltwater to infiltrate freshwater sources. Urbanization, in particular, can lead to increased impermeable surfaces, reducing the area available for water absorption and exacerbating the problem.
5. Poor Water Management Practices
Inefficient water management practices can also contribute to salinity ingress. Inadequate irrigation techniques, excessive water wastage, and the lack of proper drainage systems can lead to the accumulation of salts in soil. Over time, these salts can build up and make the land unsuitable for the agricultural environment, further intensifying the issue.
Effects or Consequences of Salinity Ingress
1. Agricultural Devastation
One of the most palpable consequences of salinity ingress is its devastating effect on agriculture. As saltwater infiltrates arable land, it leaves behind a saline legacy. High levels of salt in the soil render it unsuitable for most crops, leading to reduced agricultural yields and, in some cases, complete crop failures. This agricultural devastation threatens food security for coastal communities and beyond.
2. Ecosystem Disruption
Coastal ecosystems, rich in biodiversity and ecological value, face dire consequences from salinity ingress. Mangroves, estuaries, and wetlands, often referred to as "nurseries of the sea," are particularly vulnerable. Increased salinity disrupts the delicate balance of these ecosystems, jeopardizing the habitats of numerous marine biodiversity. The ramifications extend to fisheries, as the decline in fishery resources affects both livelihoods and food supplies.
3. Drinking Water Contamination
The contamination of freshwater sources due to salinity ingress has dire implications for communities reliant on these sources for drinking water. As saltwater infiltrates groundwater reservoirs and surface water bodies, it compromises water quality. High levels of salinity make water unsafe for consumption, necessitating costly treatment processes or the search for alternative water sources.
4. Infrastructure Vulnerability
Saltwater, with its corrosive properties, poses a significant threat to infrastructure in coastal areas. Roads, bridges, buildings, and pipelines are susceptible to degradation and damage. Maintenance costs skyrocket as governments and communities grapple with the ongoing battle against infrastructure deterioration.
5. Economic Crisis
The economic consequences of salinity ingress are far-reaching. Agriculture-dependent economies suffer from reduced crop yields, while coastal tourism may decline due to the degradation of once-pristine beaches and ecosystems. Moreover, the costs associated with adapting to and mitigating the impacts of salinity ingress can place a heavy burden on local and national budgets.
6. Human Displacement
In some extreme cases, the consequences of salinity ingress can force communities to abandon their ancestral homes. Rising sea levels and the persistent encroachment of saltwater can lead to the displacement of coastal populations, creating a humanitarian crisis that demands resettlement and infrastructure development in safer areas.
V. Senapathi, S. Sekar, P. Viswanathan and C. Sabarathinam (2022).Groundwater Contamination in Coastal Aquifers, Elsevier, 9-18, https://doi.org/10.1016/B978-0-12-824387-9.00019-0.