Salt Front
Location of the Salt Front

The below graphic shows the current location of the salt front in relation to several other sites along the river. Estimates of the salt front are based on provisional data and subject to change if better data becomes available.

This graph is updated weekly, usually on Mondays.

The current location of the salt front. Graphic by the DRBC.

(RM=  river mile)

Next Scheduled Update: December 16, 2024

Click here for daily data
Learn More about the Salt Front


What is the Salt Front?

One important metric for understanding salinity concentrations in the Delaware Estuary (the tidal Delaware River & Bay) is the seven-day average location of the salt front, the 250 mg/L chloride concentration based on drinking water quality standards.

The salt front indicates water that is not safe to be used for drinking water because it is too salty. Because there are no dams on the Delaware River, ocean derived saltwater can move up the Delaware River from the Delaware Bay. While you cannot see the salt front, its location fluctuates in response to changing freshwater inflows, which either dilute or concentrate chlorides in the river.

Its average location is around Wilmington, Del. (see above graphic)


DRBC Management of the Salt Front

Freshwater flowing downstream from the non-tidal Delaware River helps repel, or flush back, the salt-laced ocean water. Philadelphia and New Jersey both have drinking water intakes on the Delaware River about 10 miles upstream from the Ben Franklin Bridge.

DRBC has adopted criteria, monitors chlorides, manages freshwater flows and tracks the salt front to control the upstream migration of salty water, ensuring water quality in the upper estuary remains suitable as a source of drinking water and protective of aquatic life. Salty water can also corrode industrial intakes and other infrastructure, which can be expensive to mitigate and therefore another reason for management.

Because the primary focus is to manage the upstream migration of the salt front, it is not tracked below RM 54.


Keeping Freshwater Flowing Downstream: the Trenton Flow Objective

As mentioned above, the DRBC manages freshwater flows to help maintain the salt front downstream of drinking water and other industrial intakes on the Delaware River.

A minimum flow objective at Trenton, N.J. of 3,000 cfs has been established by the DRBC to ensure enough freshwater is flowing downstream to keep the salt front from advancing too far upstream. This flow objective is met by either natural flow or by releases from upstream reservoirs during dry conditions.

DRBC has the primary responsibility to manage the salt front and meet the Trenton flow objective; this is accomplished through directed releases from water that is stored in the U.S. Army Corps of Engineers' Blue Marsh and Beltzville reservoirs, located in Pennsylvania along the Schuylkill River in Berks County and the Lehigh River in Carbon County, respectively. While DRBC does not own these reservoirs, the Commission owns storage in them for flow management purposes.

Three additional reservoirs, Pepacton, Neversink and Cannonsville, which are owned by New York City and located in the Delaware River's headwaters in the Catskill Mountains in New York State, also have storage that can be used to meet the Trenton flow objective. Releases from these reservoirs are made by the Office of the Delaware River Master.


Additional Resources
Animated Graphics: See the Salt Front Move

These graphics can also be viewed on our YouTube page: https://www.youtube.com/user/DelRivBasinComm/videos


1960s Drought

The drought of the 1960s is still considered the Basin's drought of record. DRBC was newly formed in 1961, and its experience managing the Basin's water resources during this drought helped form its flow management programs that are used today.

This animated graphic shows the movement of the salt front in the Delaware River Estuary during the months of July 1964 through January 1965. The Delaware River Basin was extremely dry during these months, allowing the salt front to travel upstream to river mile 102, just 8 miles south of Philadelphia's drinking water intakes on the Delaware River. River mile 102 was the highest recorded location of the salt front.


 

 


This animated graphic shows the movement of the salt front in the Delaware River Estuary during the months of July through November 1965. The Delaware River Basin was dry during these months, allowing the salt front to travel upstream to approx. river mile 95, just a few miles north of the Schuylkill River's confluence with the Delaware River.

 

 


2002 Drought

This animated graphic shows the movement of the salt front in the Delaware River Estuary during the months of July through November 2002. The Delaware River Basin was dry during these months, allowing the salt front to advance upstream to river mile 89 near the Philadelphia International Airport.

 

2017: Normal Hydrologic Conditions

This animated graphic shows the movement of the salt front in the Delaware River Estuary during the months of July through November 2017. The Delaware River Basin experienced normal hydrologic conditions during these months; the salt front never reaches the Commodore Barry Bridge, staying mostly within its median range.