Saltwater may pollute 75% of coastal freshwater by 2100

Sea-level rise is taking a visible toll on coastal communities, but we should also be worried about what’s happening below our line of sight, as troubling new research shows.

New research from NASA’s Jet Propulsion Laboratory (JPL) and the US Department of Defense (DOD) shows that seawater will contaminate groundwater in approximately 75 percent of the world’s coastal areas by the end of the century. published at the end of last month Geophysical Research Lettershighlight how rising sea levels and decreasing precipitation contribute to saltwater intrusion.

Groundwater and saltwater in the ocean maintain a unique balance under the coastlines. The balance is maintained by the internal pressure of the ocean, as well as rainfall that replenishes the freshwater aquifers (layers underground that hold water). there is a certain overlap, known as the transition zone, the balance is usually maintained by each body of water on its own.

Climate change, however, gives salt water an advantage in the form of two environmental changes: rising sea levels and decreased rainfall due to global warming. salt water intrusion caused by rising sea levels.

Saltwater intrusion is exactly what it sounds like. when saltwater infiltrates land more than expected, often endangering freshwater resources such as aquifers.

To study the future reach of saltwater intrusion, JPL and DOD researchers analyzed how rising sea levels and reduced groundwater recharge would affect more than 60,000 coastal watersheds (areas that drain water from features such as rivers and streams into a shared body of water). around the world by 2100.

As detailed in the study, the researchers concluded that by the end of the century, 77% of the coastal watersheds studied will be affected by saltwater intrusion due to the above two environmental factors.That’s three out of every four coastal regions assessed.

The researchers also looked at each factor separately. For example, sea-level rise alone would move saltwater inland in 82% of the coastal watersheds considered in the study, specifically pushing the freshwater-saltwater transition zone back as much as 656 feet (200 meters) by 2100. Low-lying regions such as this phenomenon Southeast Asia, the Gulf Coast, and parts of the US East Coast are particularly at risk.

On the other hand, slower groundwater recharge would allow saline intrusion in only 45% of the studied watersheds, but would push the transition zone landward by up to three-quarters of a mile (about 1,200 meters). Areas including the Arabian Peninsula, Western Australia, and Baja California, Mexico. peninsula, will be vulnerable to this phenomenon However, researchers also noted that groundwater recharge will actually increase in 42% of the remaining coastal watersheds, in some cases even dominating saltwater intrusion.

“Depending on where you are and what’s dominant, the implications of your management can change,” said Kyra Adams of JPL and one of the study’s co-authors. statementciting sea level rise and aquifer depletion.

Sea-level rise is likely to affect saltwater intrusion on a global scale, while groundwater recharge will dictate the depth of local saltwater intrusion, but the two factors are closely related.

“With saltwater intrusion, we see that sea-level rise increases the baseline risk of changes in groundwater recharge becoming a serious factor,” said Ben Hamlington of JPL, who also led the study.

Global climate approaches that take local climate impacts into account, such as this research, are important for countries that do not have sufficient resources to conduct such research on their own, the team stressed, and “those with the fewest resources suffer the most.” . due to sea level rise and climate change,” Hamlington added.

The end of the century may seem like a long time, but if nations and industries are to mobilize in response to these predictions, the year 2100 will be upon us sooner than we think.