Delaware • New Jersey • Pennsylvania
New York • United States of America
- Aquatic Life Designated Use Study
- Bacteria Monitoring
- Biomonitoring Program
- Chlorides Monitoring
- Contaminants of Emerging Concern
- Delaware Estuary Water Quality Monitoring Program
- Dissolved Oxygen and Nutrients
- Modeling
- Other Monitoring Programs & Studies (e.g., Fish Tissue, Microplastics, Metals)
- PCBs and PMPs
- Special Protection Waters (SPW)
- Water Resource Data Sets
- A Water Quality Concern
- The Salt Front
- Monitoring Chlorides in Special Protection Waters
- Winter Chloride Monitoring in Tidal Delaware River
- Additional Resources
Why Care about Chlorides?
- Chlorides found in water and wastewater at elevated concentrations can impart a salty taste to drinking water and potentially impact public health.
- Salinity levels also affect aquatic life and other living resources.
The DRBC has adopted criteria and monitors chlorides to ensure water quality remains suitable as a source of drinking water and protective of aquatic life.
- Visit https://drbc.net/Sky/waterq.htm (scroll down ~halfway) to view comparison of estimated chloride concentrations to criteria for water quality zones 2 and 3 (link to map of zones; pdf).
In the Delaware River Estuary, salt water mixes with freshwater.
Higher chloride concentrations indicate the degree to which ocean derived saltwater has moved into the freshwater portion of the upper estuary, near Philadelphia and Camden, where drinking water intakes are located.
In addition to impacting treatment costs for public water suppliers, salty water increases corrosion control costs for other surface water users, for example, industry.
Monitoring the Salt Front
DRBC's Hydrology/Flow Management Program focuses on controlling the upstream migration of salty water from the Delaware Bay during low-flow conditions to protect drinking water.
One important metric that is monitored 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's location fluctuates in the Delaware River Estuary as streamflows increase or decrease in response to changing inflows, which either dilute or concentrate chlorides in the river.
Climate Change
DRBC is studying the potential affects of sea level rise on chloride concentrations in the Delaware River Estuary and Bay.
Will sea level rise force the salt front upstream? Will more freshwater coming downstream be needed to repel the salt front? Will additional reservoir storage be needed for freshwater?
Staff are using rainfall-runoff models and the latest climate research to help plan for a sustainable water supply to meet future water demands in the basin.
This graph shows the increase in chlorides at the Delaware River at Trenton, N.J. Graphic by DRBC. View larger (jpg). |
Elevated chloride concentrations are also a concern in the non-tidal Delaware River, which are protected under DRBC's Special Protection Waters(SPW) regulations.
Over the past several years, instream monitoring of the non-tidal river has shown an upward trend in chloride concentrations.
While concentrations are still below criteria for drinking water and aquatic life use, the DRBC is watching this trend closely.
This trend is not just seen in the Delaware River's freshwater, it is becoming commonplace in areas of the U.S. with significant roadway de-icing activity. Studies suggest that chloride concentrations in winter are as much as a hundred-fold over summertime levels. Also, higher chloride concentrations increase as a function of impervious surface.
Additional monitoring and investigation into sources, mitigation measures and de-icing alternatives to salt and brine are needed.
Study: 2021-2023
From 2021 - 2023, the DRBC performed a two-year study to monitor chlorides, other ions and TDS concentrations in the non-tidal Delaware River watershed.
A mix of mainstem and tributary locations were chosen, for a total of 27 sites.
• View Map of Monitoring Locations
• Monitored Ions included: chlorides, TDS, nitrate, calcium, magnesium, sodium, potassium, sulfate, total silica, total alkalinity, total suspended solids and total phosphorus
At seven tributary sites, DRBC deployed continuous specific conductance and temperature loggers; the remaining sites already have continuous data being collected.
To complement the continuous data collection, staff sampled each site once monthly for conductivity and temperature. The loggers were maintained regularly throughout the study period.
A report is forthcoming.
SIFT Workgroup
In 2022, the DRBC formed the Salinity Impacts Freshwater Toxicity (SIFT) Workgroup to collaboratively sift through the escalating issue of freshwater salinization and increasing chlorides in rivers and streams and discuss regulatory and road salt management options. The workgroup is made up of DRBC partner agencies, ngos and a few consulting groups and is meeting quarterly.
Looking Ahead
In 2024, for the second phase of this project, staff identified a subset of the 2021-2023 non-tidal chloride monitoring sites for further and more frequent monitoring. Twice monthly monitoring at 10-15 tributary locations will begin in October 2024 and go through winter. Monitoring will be done using continuous conductivity loggers, and grab water samples will be collected for chloride, magnesium, potassium, sodium and other ions. Additional components of this phase of the study include outreach to highlight areas of concern, troubleshoot probable causes of degradation and educate the public about the issue.
One of the applications on the DRBC's water quality dashboard pulls real-time USGS chloride data and compares it to water quality criteria for DRBC water quality zone 2. Data show that criteria exceedances do occur when winter storms are timed with periods of low flow.
- Check out the Dashboard: https://drbc.net/Sky/waterq.htm
During the winter months of 2024-2025, the DRBC is going to - when conditions warrant - monitor chloride data with grab samples from the Bristol Wharf (located in water quality zone 2). Samples will be collected once per day during the storm event and will end when exceedences are confirmed or deemed no longer likely.
DRBC Presentations/Information
- Chlorides Management and Monitoring (pdf; given at the April 2024 Water Quality Advisory Committee Meeting)
- Restoring Water Quality in the Main Stem Delaware River: Programs, Policies and Strategies (presentation given by DRBC staff at the 9th Annual Delaware River Watershed Forum, Sept. 2021; pdf 3.6 MB)
- Non-Tidal Chloride Monitoring 2021-2023 (presentation given at the Nov. 2020 joint MACC-STAC Meeting; pdf 6 MB)
- A Fishable, Swimmable (and Drinkable) Delaware River Estuary (presentation given at the Sept. 2020 Delaware River Watershed Forum; pdf 6.7 MB)
- Evaluation of SPW Chloride Data (presentation given at the July 28, 2020 WQAC Meeting; pdf 3 MB)
- History of the Salt Front (presentation given at the October 2019 CDRW Forum; pdf 2 MB)
- Chloride Trends (presentation at the March 29, 2018 WQAC Meeting; pdf 1.4 MB)
- Graphic showing chloride concentrations from 2014-2018 in Delaware Estuary Water Quality Zone 2 as compared to DRBC criteria (png 17 KB)
- Chloride and/or sodium concentrations in Delaware Estuary Water Quality Zones 2 and 3 as compared to DRBC criteria (link to DRBC water quality graphs using R scripts; scroll down for chloride graphs)
- DRBC Delaware Estuary Water Quality Zones (jpg 364 KB)
Additional Links of Interest
- USGS: Chlorides, Salinity, and Dissolved Solids
- USGS Publication: Long-term impacts of impervious surface cover change and roadway deicing agent application on chloride concentrations in exurban and suburban watersheds (August 2022)
- Alternatives to Salt for Treating Icy Sidewalks and Driveways
- Road Salt Articles from the Stroud Water Research Center
- Penn State Extension: Environmental Hazards of Road Salt
- Tookany/Tacony-Frankford Watershed Partnership: Road Salt Fact Sheet
Copyright © Delaware River Basin Commission,
P.O. Box 7360, West Trenton, NJ 08628-0360
Phone (609)883-9500; Fax (609)883-9522
Thanks to NJ for hosting the DRBC website