- Also called:
- saline intrusion
- Related Topics:
- seawater
- sea level rise
- groundwater
- aquifer
- freshwater
saltwater intrusion
-
What is saltwater intrusion?
Saltwater intrusion is an ecological issue where salt water infiltrates fresh water sources in coastal regions, which can alter landscapes and harm agriculture. This is a growing problem in coastal communities worldwide, with impacts ranging from economic losses due to ruined land to humanitarian crises from lack of drinking water.
The primary cause of saltwater intrusion is rising sea levels from global warming. Other factors include diverting rivers for irrigation and over-pumping groundwater, which reduces freshwater pressure and allows saltwater to invade aquifers, contaminating wells. Effects include threats to drinking water and agriculture. High sodium levels in drinking water can cause health issues, while saltwater intrusion in agriculture can lead to freshwater salinization, which harms plant life and contaminates water.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does saltwater intrusion happen in natural environments?
Saltwater intrusion, an ecological problem, occurs when saltwater infiltrates fresh water sources in coastal areas. Rising sea levels from global warming are a significant cause, with the rate of increase doubling in the 21st century to over 3 mm per year. This issue is worsened by extreme weather events like droughts and storms, which are becoming more frequent due to climatic changes. Droughts cause land to absorb more salt, while intense storms and floods push saltwater further inland, contaminating freshwater supplies. The diversion of rivers for irrigation and excessive groundwater withdrawal also contribute to saltwater intrusion, reducing water pressure in freshwater aquifers and allowing saltwater to encroach.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why is saltwater intrusion a problem for freshwater ecosystems?
Saltwater intrusion poses a significant threat to freshwater ecosystems by infiltrating and contaminating fresh surface water and groundwater, increasing salinity, and damaging the land. Increased salinity in freshwater sources can make the water unsuitable for drinking, food production, and most domestic and industrial uses.
Saltwater intrusion can also lead to freshwater salinization syndrome, where high salt concentrations mobilize pollutants in the water and soil. This can cause nitrogen and other nutrients to flow into water bodies, promoting algae growth. Algae population explosions and subsequent die-offs deplete oxygen in the water, threatening the survival of aquatic life.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does saltwater intrusion affect plants and animals in affected areas?
Saltwater intrusion, the infiltration of salt water into freshwater areas, poses a significant threat to both plants and animals. In agricultural areas, it leads to freshwater salinization, where high salt concentrations mobilize pollutants, such as nitrogen, resulting in algae blooms that deplete oxygen and threaten aquatic life.
Elevated salinity inhibits plant growth by causing dehydration and hindering nitrogen uptake, which deteriorates soil and reduces farmland productivity. The increased salinity in freshwater sources also makes the water unsuitable for drinking, thus affecting human health and increasing water scarcity. Exposure to elevated sodium levels can stress the kidneys and contribute to hypertension, heart disease, and dementia.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What human activities can increase the risk of saltwater intrusion?
Human activities significantly contribute to the risk of saltwater intrusion, an ecological problem where salt water contaminates fresh water supplies.
Activities that increase this risk include:
* Global warming, which raises sea levels due to thermal expansion and melting ice. This leads to more frequent extreme weather events, such as droughts, storms and floods, that worsen saltwater intrusion.
* The diversion of rivers for irrigation lowers water levels, enabling saltwater to migrate upstream.
* Over-extraction of groundwater reduces pressure in freshwater aquifers, allowing saltwater to infiltrate and contaminate wells.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What solutions or methods can help prevent or reduce saltwater intrusion in the environment?
Saltwater intrusion, an ecological issue where saltwater contaminates freshwater sources, poses a significant threat to coastal areas worldwide.
Mitigation strategies can be costly, potentially involving millions of dollars for constructing desalination plants, pipelines, and water storage facilities. Prevention measures include implementing water-management plans to reduce freshwater withdrawals, building coastal sea walls, and planting native vegetation for erosion control. Injection wells can also recharge aquifers with freshwater, counteracting saltwater advancement.
In affected agricultural lands, farmers are exploring salt-tolerant crops like barley as alternatives to traditional crops. While arable land may be lost, opportunities exist for conservation, wildlife habitat development, and native planting to prevent further erosion and invasive species. These efforts can also create carbon storage areas, which help to mitigate future global warming effects.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
saltwater intrusion (SI), ecological problem produced by the encroachment and infiltration of salt water (typically brackish water or seawater) into the fresh surface water and groundwater supplies of coastal areas. Saltwater intrusion can alter the landscape, damage the potential to use the land for agriculture, and contaminate freshwater supplies. It has become a serious issue in several seaside communities around the world, including China’s Yangtze River estuary, the East Coast of the United States, the Netherlands and Italy in Europe, and Algeria and Egypt in North Africa. The effects of saltwater intrusion can be as varied as economic losses caused by the fouling of once arable land and substantial humanitarian crises created by a declining supply of potable water. Since each location is characterized by a unique set of geographic, climate, natural resource, and population circumstances, the scope and effects of saltwater intrusion may differ between sites, but increased salinity can ruin wells, groundwater basins, and aquifers, all of which can lead to a scarcity of freshwater resources used for drinking and irrigation.
Causes
The most common cause of saltwater intrusion is a rise in global sea level due to global warming. Since 1880 global average sea level has risen 21–24 cm (8–9 inches). The rate of increase doubled in the 21st century and now stands at an increase of more than 3 mm (0.1 inch) per year. Low-lying island countries such as Kiribati are among the most threatened by sea level rise. Many of the country’s 33 islands are predicted to become uninhabitable by 2050.
As the average global temperature increases, sea levels rise due to thermal expansion and the addition of meltwater from polar ice sheets and mountain glaciers to the ocean. Climatic changes stemming from global warming is increasing the frequency of extreme weather events, such as droughts, storms, and floods, all of which worsen saltwater intrusion. In areas plagued by drought conditions, parched land is prone to soaking up more salt since little or no water is available to flush the soil. Lowered river levels also allow saltwater to migrate upstream. In addition, storms are becoming more intense, producing larger swells and greater storm surges that push water farther inland. Flooding resulting from high tides is occurring between 300 percent and more than 900 percent more frequently than it did in 1975, which sends salt water even farther upstream, contaminating more acreage and inundating low-lying communities.
" height="20" alt="HEW Logo">
Other major causes of saltwater intrusion include the diversion of rivers for irrigation (which lowers the river’s water level) and the withdrawal of too much groundwater from freshwater aquifers too rapidly. In coastal areas, when people pump water from below-ground reservoirs at a rate faster than they can be naturally refilled by precipitation, the water pressure provided by the aquifer’s fresh water declines and salt water is able to push into and contaminate the aquifer, rendering the wells above useless. For example, on Hilton Head Island, in South Carolina, only two of a dozen original underground wells used to supply drinking water remained operational as of 2024; the others have been overtaken by salt water.
Effects
One of the most worrisome effects of saltwater intrusion is the threat to drinking water supplies. Exposure to elevated sodium in foods and other sources stresses the kidneys and contributes to a variety of health problems, including hypertension, heart disease, calcium loss, and dementia; adding sodium and other salts to the body through drinking water increases the risk of and exacerbates these problems. The World Health Organization’s suggested drinking water guideline is 200 parts per million, which contrasts with the U.S. Environmental Protection Agency’s recommended sodium advisory of 30–60 parts per million for drinking water.
Saltwater intrusion into agricultural areas is also concerning, since it can lead to freshwater salinization syndrome, a process by which high concentrations of salt in the water can cause other pollutants in the water and soil to become more mobile or more concentrated. For example, nitrogen, a common farming byproduct, is freed from the soil by salt. Once freed, nitrogen and other nutrients like it flow into connecting bodies of water, where they encourage algae growth; explosions in the algae population and subsequent die-off depletes the oxygen in the water, which threatens the survival of plants, fish, and other forms of life.
Mitigation
Mitigation of saltwater intrusion can cost communities millions of dollars and involve building reverse osmosis or desalination treatment plants, pipelines to transport fresh water from new sources, and water storage facilities. Prevention can also be expensive, especially for small communities. The first line of defense is to implement water-management plans that reduce freshwater withdrawals, create coastal sea walls, and plant native plants to serve as erosion controls. In addition, in areas with wells that are threatened with contamination, some communities have opted to sink injection wells—which pump in fresh water—to recharge aquifers and prevent the advance of salt water.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
In places where coastal farmland is being replaced by brackish marshes, farmers are being forced to experiment with salt-tolerant crops, either different strains of their current crops or different crops entirely, barley instead of corn, for example. Although the arability of the land is lost, the potential exists for conservation, wildlife habitat development, and native planting, often of tidal grasses, to help stop further soil erosion and to stop invasive species from gaining a foothold. Losses suffered by farmers in coastal areas may still be immense, but there exists some opportunity to create a carbon storage area, which marshes are prized for, and potentially allay some future damage associated with global warming (see also carbon sequestration).