Delaware River Salt Front Moves Upstream as Drought Cuts Flows
Reservoir releases can slow the front, but reduce available amount of drinking water — already in scant supply — in the process
Salty water from the Delaware Bay has crept up the Delaware River toward a drinking water intake plant at Delran, and is now at its highest point since 2010 because low river flows in the recent dry spell have been too weak to prevent the so-called salt front from moving upstream, officials said.
The salt front was at river mile 85, between Chester, PA, and Philadelphia International Airport at the latest reading on October 20, making it 13 miles farther upstream than it normally is at this time of year, the Delaware River Basin Commission (DRBC) said on Wednesday.
While the salt front was still 25 miles downstream from the Delran intake, officials are now considering how to prevent the salty water moving farther upstream while conserving reserves in two Pennsylvania reservoirs that have been used to boost river flows since early September. The reservoir releases are designed to compensate for the sluggish natural flows that have been caused by a lack of rain, and to prevent the salt front from moving farther upstream.
On October 21, the New Jersey Department of Environmental Protection declared a drought warning for 14 northern and central counties, enabling officials to direct water transfers among systems, control releases from reservoirs, and modify stream flows, with a view to preventing more serious water shortages in affected areas. It also urged residents and businesses to reduce water use.
“We want to keep it away from the intakes, for sure,” said Clarke Rupert, a spokesman for the DRBC, which regulates water supplies in the Pennsylvania, New Jersey, New York, and Delaware portions of the basin.
The Delran plant is run by New Jersey American Water, and meets 50 percent to 60 percent of demand from that company’s customers in Burlington, Camden, and Gloucester counties, said Anthony Matarazzo, senior director of water quality and environmental management.
Matarazzo said that if salty water ever got into the Delran intake, it would be possible to treat it by using more chlorine — as is often done for water that has been affected by road salt in the winter — although that is likely to lead to customer complaints about taste and odor.
Without chlorine treatment, some other customers will complain about a salty taste to the water, he said.
“Generally, chlorides and sodium don’t cause us any treatment issues,” he said. “We can deal with it in our treatment plant.”
He’s more concerned about the possibility that DRBC officials will release more water from reservoirs to boost river flows rather than for its intended purpose as drinking water.
“We’re going to use that water to suppress that salt line for ecological benefits,” Matarazzo said, referring to the DRBC’s release of water from the Pennsylvania reservoirs. “It’s necessary but it’s hard to watch that happen. You are taking fresh water out of storage, and you’re not using it for drinking water purposes.”
In response to the prolonged shortage of rainfall, DRBC officials have been releasing water from Pennsylvania’s Beltzville and Blue Marsh reservoirs in an effort to maintain water flows in the river. Officials aim to maintain the volume of the river at Trenton at 3,000 cubic feet per second.
The reservoir levels have now dropped near the point at which officials will be required to reduce their withdrawals, Rupert said. That would cut the flow volume, at Trenton and further reduce the river’s resistance to the salt front.
While the water level in the Beltzville reservoir is now below the point that requires officials to reduce water withdrawals, the Blue Marsh reservoir is slightly above that limit. Regulations require both bodies of water to be below specified limits in order for withdrawals to be cut.
If the dry conditions continue, the DRBC must balance a requirement to conserve water levels in the reservoirs with a need to stop the salt front moving farther up the river.
Those actions could be triggered if DRBC declares a drought warning which it said on Wednesday was “becoming likely” for the lower basin downstream of Montague, NJ.
A drought warning would reduce the targeted flow at Trenton to 2,500-2,900 cubic feet per second, depending on the location of the salt front, Rupert said. If the salt front moves above river mile 92.5 — about seven miles upstream from its location on October 20 — officials would aim for a flow of 2,900 cubic feet per second.
Declaring a drought warning would also give DRBC the option of drawing water from Lake Wallenpaupack near Hawley, PA, and from Merrill Creek Reservoir near Phillipsburg, NJ, but only if the targeted and actual flows at Trenton fell below 3,000 cubic feet per second for five consecutive days, the DRBC’s Rupert said.
The salt front, defined as a concentration of at least 250 milligrams per liter of chloride, is the farthest upstream since 2010 when it reached river mile 86. It is still below its highest recorded level at river mile 102, two miles north of the Ben Franklin Bridge, during the “drought of record” in the 1960s. And it is even farther from the drinking water intakes at river mile 110 on both sides of the river.
But the prolonged dry spell, which has prompted New Jersey, Pennsylvania, and New York to declare drought warnings in about half of their “basin states” (the part of the state that is in the Delaware River basin), has prompted officials to consider the consequences of continued low flows in the river.
Rainfall in north Jersey counties bordering the Delaware River has been 75 percent or more below normal in October, while the basin’s South Jersey counties have seen rainfall as much as 50 percent below normal, according to the National Weather Service.
Steve Tambini, executive director of the DRBC, warned of further possible declines in reservoir levels. “If more water is needed to address salt-front management, we can expect additional declines in reservoir storage,” he said in a statement. The last time the DRBC declared a basin-wide drought emergency was in 2001-2002 when the salt line rose to river mile 89.
The DRBC will be holding a public meeting on November 9 to discuss current conditions and how to address them.