Ocean saltwater entering Delaware River due to drought and sea level rise, water managers say

Water managers in the Delaware River Basin are sounding the alarm as ocean saltwater is advancing further upstream into the river, a consequence of ongoing drought conditions and rising sea levels. This growing crisis poses a significant threat to drinking water supplies for millions of residents in Pennsylvania, New Jersey, and Delaware.

The Delaware River’s freshwater flows typically keep ocean saltwater at bay, maintaining a delicate balance. However, reduced rainfall has weakened this barrier, allowing salty ocean water to intrude farther inland. Compounding the problem, rising sea levels due to climate change make it harder for the river to naturally repel the encroaching saltwater, heightening the risk for communities that depend on its freshwater.

Philadelphia and neighboring towns that rely on the river for municipal water are at risk of seeing elevated salt levels, which could overwhelm water treatment systems. Prolonged saltwater intrusion may force costly adaptations, such as advanced desalination technologies or importing water from alternative sources. Industries dependent on the river, including power plants and chemical manufacturers, face potential disruptions. Increased salinity can damage infrastructure, such as pipes and machinery, and affect processes requiring freshwater.

Regional water authorities are responding by planning releases from upstream reservoirs to bolster freshwater flows and push the “salt line” back toward the sea. These short-term fixes are part of broader strategies to combat the dual threats of climate change and drought.

“Saltwater intrusion is a growing challenge that underscores the need for sustainable water management and climate resilience,” said officials from the Delaware River Basin Commission. The situation mirrors similar challenges faced by other rivers around the world, from the Nile to the Mekong, where saltwater intrusion threatens agriculture, ecosystems, and water supplies.

With predictions of more frequent droughts and continued sea-level rise, experts warn that the Delaware River Basin must adopt long-term strategies to secure water resources for future generations.