East Coast Has a New Drought Worry

Salty ocean water is creeping up the Delaware River, the source for much of the drinking water for Philadelphians and millions of others, brought on by drought conditions and sea level rise, and prompting officials to tap reservoirs to push the unpotable tide back downstream. Officials say drinking water isn't imminently at risk yet, but they're monitoring the effects of the drought on the river and studying options for the future in case further droughts sap the area, per the AP.

• What is the salt front? The salt front, or salt line, is where salt water from the ocean and fresh water meet in the river. That boundary is typically somewhere around Wilmington, Delaware, but the recent drought has pushed it about 20 miles north.

• Why does it matter? The farther the line moves upstream, the closer it gets to drinking water intakes, which officials have worked for decades to avoid. The Delaware River provides drinking water for some 14 million people, including most of Philadelphia but also New Jersey and New York. Still, the line is south of those intakes and below the level it traveled in the 1960s during record drought. Desalination of salt water is costly and energy intensive and can create new issues, such as where to dispose of the highly concentrated salt brine pulled from the water.
• Encroaching salt: Officials control the salt line by releasing water from two reservoirs, which pushes the front downriver. The flow that officials target is roughly equivalent to the amount of water in two Olympic-size swimming pools flowing by per minute.
• Precedence: The salt front last reached roughly where it is now in 2016 during another drought.
• Elsewhere in the country: The Mississippi River similarly saw what officials call a "salt wedge" in 2023, resulting in heightening underwater levees and bringing in drinking water.
• Has recent rain helped? Yes, but not enough. The river needs about an inch of rain a week for a time to move the line back to its normal location.
• How are officials planning for the future? The Delaware River Basin Commission, a federally created agency run by Delaware, New Jersey, New York, and Pennsylvania that manages the river's resources, is studying the impact of climate change and considering other options, including additional storage. Water managers are starting to consider more serious conservation measures as well. "I would say the East is not water-rich, we're water adequate, and we need to recognize that," says water resource operations manager Amy Shallcross.

(More Delaware River stories.)