Delaware River water levels at 60% as salt front increases amid drought

Parched farms, wildfires, and browned vistas are highly visible signs of this fall's drought.

Less visible: Water flow in the Delaware River, which dropped to 60% at Trenton, the regional agency that oversees the river's use said Tuesday.

Officials with the Delaware River Basin Commission (DRBC) said they have released billions of gallons of water from upstream reservoirs to keep the river to acceptable levels in Philadelphia, but that protective measures might have to be taken if conditions persist. That could include reducing more reservoir releases, or diverting water from elsewhere.

DRBC officials said during a virtual public hearing on the drought that salt front in the river has encroached well above its normal level near Wilmington. Currently, it is near Philadelphia International Airport. The salt front is a metric that shows salinity in the tidal portion of the river.

Philadelphia pulls drinking water from the river at its Samuel S. Baxter Water Treatment Plant in Torresdale, which is about 20 miles above the airport.

'Repel salinity'

The DRBC watches to ensure the salt front does not encroach that far. The front, which moves upriver during a drought without freshwater to push it down, indicates water that is not safe to drink. Currently, the front is at mile marker 89. The Philadelphia intake is at mile marker 110. The front is normally at mile marker 70.

The front has not reached the Schuylkill since a drought in the 1960s when it reached mile marker 102.

"Our operations are designed to preserve regional storage and repel salinity," said Amy Shallcross, manager of the DRBC's water resource operations.

The DRBC made a presentation of drought conditions on the 330-mile waterway during Tuesday's special virtual public hearing. Officials said that they would decide whether protective actions are needed either at a special meeting on Nov. 21, or a regularly scheduled meeting on Dec. 5.

Much of the Philadelphia region began falling into dry conditions in August, with the drought taking hold in September and a record-dry October, though some reservoirs upstream have seen more rain.

A heavy rain was expected to sweep through the Philly region Wednesday night, and should help boost river flow, but it's unclear how much of a lasting impact it will have. Some parts of the region face a 10 inch rain deficit.

Reservoirs to the rescue

The Delaware River begins in New York, runs the border along Pennsylvania and New Jersey, and enters Delaware. The DRBC can pull from a system of reservoirs that begin in New York. But many of the streams that feed those reservoirs are well below normal.

Tens of billions of gallons of water have been released from New York City reservoirs to keep the river flow from falling too low. Water has also been released from the Beltzville Reservoir in the Lehigh Valley to keep the flow at Trenton acceptable.

"So you can see we've been adding a lot of water to the system or to the river to maintain flow," Shallcross said.

Currently, she said, reservoirs for New York City, which gets a portion of its drinking water from the Delaware River, are between 35% and 63% full. Meanwhile, reservoirs in Beltzville in the Lehigh Valley, and Blue Marsh, in Berks County, are 79.7% and 75.4% full.

Shallcross said low rainfall and normal releases have combined to reduce reservoir storage.

The salt front is in about the same location as it was during a 2016 drought, which ended in about December that year, she said. So officials are watching short- and long-term forecasts, as well as a La Nina winter pattern, which tends toward a wetter and warmer winter.

The seasonal outlook, according to the National Oceanic and Atmospheric Administration, gives the East Coast about even chance of an above or below average precipitation for the winter, with temperatures leaning above normal. The long-term forecast calls for the drought to persist in November, but for conditions to likely improve in the winter.

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