Saltwater Intrusion
What is it, and why is it dangerous?
Written by one of our excellent interns, Everett Tompkins
On many coasts, unfortunately, a process called saltwater intrusion can occur, where saltwater can contaminate wells. The sucking out of water from the ground limits the freshwater’s ability to deflect the saltwater back towards the ocean, causing the saltwater level to rise. The picture below can illustrate this phenomenon.
Source: USGS.gov, Public Domain
Due to changes in the climate, the rise of ocean water relative to the water table of fresh water can increase the risk of saltwater intrusion. By using recent metrics from sources such as the U.S. Geological Survey, water managers can limit and prevent saltwater intrusion.
But why should we worry? Firstly, it can be dangerous for our bodies. For adults with high blood pressure, a maximum of 1,500 mg of sodium per day is recommended. The EPA limit sodium to 250 mg/L for water; an adult would get 500 mg of sodium a day just from their water, contributing to ⅓ of their maximum recommended daily intake. For Maryland, a coastal state, 32.2% of adults have high blood pressure. Additionally, salt in water can increase the mobility of metals such as cadmium, copper, and lead in both infrastructure and soil. These can cause kidney damage, liver damage, and brain damage. Second, it can be hazardous to infrastructure. Chloride, a component of salt, can prevent the formation of protective layers on metal, making the metal more prone to corrosion. This corrosion can cause an increase in water contamination and thinning of plumbing materials.
Works Cited
Bui, Tiffany. “Salt: Health and Safety.” Clean Water Action, Clean Water Action, 29 September 2021, https://cleanwater.org/2021/09/29/salt-health-and-safety. Accessed 4 June 2025.
Water Resources Mission Area. “Saltwater Intrusion.” U.S.G.S. | Science for a changing world, U.S. Geological Survey, 2 March 2019, https://www.usgs.gov/mission-areas/water-resources/science/saltwater-intrusion. Accessed 4 June 2025.