While officials currently assert that the drinking water is not immediately threatened, they are closely observing the drought’s impact on the river and are exploring options for the future, preparing for further dry spells that could affect the region.
A closer examination of this advancing salt front reveals its significance to the ecosystem. The salt front, or salt line, marks the convergence of saline ocean water and freshwater within the river system. Normally positioned around Wilmington, Delaware, prolonged dry conditions have shifted this boundary approximately 20 miles northward to around Philadelphia International Airport.
The implications of the salt line’s movement are concerning, as it creates a risk to drinking water intake points that officials have diligently safeguarded for decades. Approximately 14 million people rely on the Delaware River for their drinking water, including the majority of Philadelphia residents, and even individuals in New Jersey and New York. At present, the salt front remains south of these crucial intakes and has not reached levels observed during severe droughts in the 1960s.
Desalinating the saltwater is not a viable alternative as the process is expensive, requires considerable energy, and poses additional challenges, such as the disposal of concentrated salt brine extracted from the water. As noted by Amy Shallcross, water resource operations manager with the Delaware River Basin Commission, “There are alternative sources, but we don’t want to be trucking in bottled water for people. We get anxious when it approaches Philadelphia, as it’s currently only 18 miles away from the drinking water intakes. It can swiftly move upstream.”
To combat the advancing saltwater, officials are actively managing the salt front by releasing water from two reservoirs, effectively pushing the salt line further downstream. The commission keeps a vigilant eye on the flow at Trenton, which is the highest upstream point influenced by the encroaching tide. Their target flow rate is comparable to having two Olympic-sized swimming pools worth of water passing by each minute; should their measurements fall short, additional water is released.
The last occasion when saltwater advanced this far up the river was in 2016, during another drought, according to officials.
This issue isn’t confined to the Delaware River basin; it is part of a larger trend where other regions nationwide also grapple with saltwater intrusion exacerbated by rising sea levels and riverbed dredging. The Mississippi River experienced a similar challenge in 2023, facing a “salt wedge” scenario which prompted authorities to heighten underwater levees and improve drinking water supplies.
The recent dry spells were catalyzed by a rainless beginning to fall in the Northeast, notably affecting the Delaware River basin. This scarcity of rain has slowed the river’s flow, allowing heavier saltwater to advance upstream.
Although recent rainfall has provided some help, it has not been enough. According to Shallcross, the river requires approximately an inch of rain per week over a sustained period to push the salt line back to its customary position.
Plans for the future are in firm development at the Basin Commission, which oversees water resources in cooperation with Delaware, New Jersey, New York, and Pennsylvania. The organization is investigating the impacts of climate change on water resources while exploring possibilities for expanding storage options. Conservation measures are also being seriously evaluated, with Shallcross emphasizing, “I would say the East is not water-rich, we’re water adequate, and we need to recognize that.”