H2O Uh-oh Saltwater contamination in freshwater systems is on the rise Salt is starting to pollute the freshwater sources people rely on. Kiley Price, Inside Climate News Mar 19, 2025 10:10 am | 1 Flooded streets in Charleston, S.C. due to an unsually high tide and offshore storm in 2021. Credit: SOPA Images Flooded streets in Charleston, S.C. due to an unsually high tide and offshore storm in 2021. Credit: SOPA Images Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn moreGlobal sea levels rose faster than expected last year, largely due to warming ocean temperatures, a new NASA analysis found.As seawater creeps further into coastlines, salt threatens to pollute the freshwater reserves that people depend on. But this brine isnt just coming from the ocean: New research shows freshwater ecosystems are facing widespread dual threats of salt contamination from the sea and land, made worse by climate change.Humans are a salty species, using the mineral for a vast number of reasonsfrom de-icing the roads during snowstorms to seasoning food.But our salty habits, coupled with rising seas, pose major threats to human health, infrastructure, agriculture and wildlife. Now, scientists are trying to help water managers better understand the salt risks that crucial water supplies face from land to sea as global temperatures warm.A salty futureWhen it comes to climate change, scientists are learning to expect the unexpected. Even so, 2024s rate of sea level rise was unusual, according to NASA.Every year is a little bit different, but whats clear is that the ocean continues to rise, and the rate of rise is getting faster and faster, Josh Willis, a sea level researcher at NASAs Jet Propulsion Laboratory in Southern California, said in a statement.Using an ocean-observing satellite, scientists measured last years global rate of sea level rise at 0.23 inches, compared to the expected rate of 0.17 inches annually. This may seem tiny, but bear in mind that even small increases in sea levels can have major consequences for coastal communities, including worsening storm surges during hurricanes.Around two-thirds of 2024s rise can be attributed to ocean warming, because seawater expands as it heats. The rest of the rise is due to an influx of water coming from ice sheets and glaciers, which are melting at unprecedented rates around the world due to climate change. Last years El Nio weather event may have also been to blame for warming up the water by impacting how heat travels vertically through the ocean, NASA scientists said.Overall, the rate of annual sea level rise has more than doubled since 1993. Global sea level has increased by 4 inches in that timeframe.It used to be that we could predict the future based on the past trends, but now we know that there are all these changes happening, Sujay Kaushal, a geologist at the University of Maryland, told me. Nothing is shocking anymore.Kaushal mostly studies the ecology of watersheds outside the ocean, such as wetlands, streams and rivers, which provide roughly 70 percent of humanitys drinking water. However, in a newly published study, he teamed up with oceanographers to see how salt from the ocean and land are affecting tidal fresh waters. Spoiler alert: Its not looking good.Essentially, salt is coming from both directionsland and the oceanand meeting in the middle, representing a double trouble issue for freshwater tidal basins, Kaushal said. The salt on land is mostly coming from wastewater, fertilizers, resource extraction and road salt.I interviewed Kaushal for a newsletter I wrote in January about how road salt is threatening water supplies and wildlife, and the data is staggering: The U.S. alone uses about 25 million tons of salt on roads each year, according to one estimate. This salt can leach into watersheds when snow melts. Typically, dilution is the solution of pollution, Kaushal says, referring to the fact that heavy rainfall or releasing fresh water from dams into ecosystems can decrease salinity.But climate-fueled droughts and rising temperatures are making this strategy more difficult. During parched periods, there is less water available to dilute the system and flush out the salt, while rising seas push salt into the watershed, a process known as saltwater intrusion.The interaction between human activities and climate change and climate variability is very, very important, Kaushal said. It amplifies the salt pulses that we see from human activity.This issue is particularly prevalent in the Delaware River, a 330-mile waterway that winds from New York to the Atlantic Ocean at the Delaware Bay. The river supplies about 60 percent of drinking water to Philadelphias 1.5 million people, but saltwater intrusion and pollution is threatening this crucial resource.The Delaware River Basin Commission has a plan in place to release water from upstream reservoirs if needed to dilute the salt. But a report released in February found that this plan may no longer be viable due to the rate of sea level rise and frequent droughts, which reporter Jon Hurdle covered for ICN earlier this month.Risk managementConsuming salty water has been linked to a number of negative health impacts in people, including high blood pressure, chronic kidney disease, dementia and reproductive risks.One of the key points in the new study is that salty water can also trigger chain reactions in ecosystems that can impact drinking water quality, infrastructure and energy and food production. If saltwater reaches the intake areas that supply freshwater to communities, it could corrode pipes used for the distribution system, power generation and heating or contaminate soils used for farming, which can kill crops.The brine can exacerbate existing issues associated with climate change, according to the study. For example, salt can release nitrogen or phosphorus from sediments in a watershed, which act as nutrients for plantspotentially leading to an overgrowth of algae and bacteria in the system, Kaushal said. Research shows that climate change can increase harmful algal blooms, which can change waters oxygen levels for fish and block sunlight from underwater plants.Currently, there are few plans or comprehensive guidance on salinization threats for people who oversee rivers, estuaries and drinking water supplies. To change this, the researchers developed a risk management framework to help officials understand where and when salinization might happen along their waterways as climate change accelerates. They zero in on methods to determine the types of hazards, probability, salt exposure and vulnerability a freshwater ecosystem may face. The Patuxent River, a tributary of the Chesapeake Bay in Maryland, for instance, has experienced high rates of salinization in recent years.Most of the management we do with water resources is reactive, Kaushal said. Were starting to realize with climate change and climate variability that we have to be proactive.This story originally appeared on Inside Climate News.Kiley Price, Inside Climate News 1 Comments