The Impact of Sea Level Rise on Salinity Intrusion in the Delaware River Estuary

In December 2025, the DRBC released a technical report that looked at how sea level rise will impact salinity intrusion in the Delaware River Estuary. A companion model calibration report was also published.

View Reports

  • The Impact of Sea Level Rise on Salinity Intrusion in the Delaware River Estuary (pdf; December 2025)

  • Three-Dimensional Hydrodynamic and Salinity Model for the Delaware River Estuary Calibration Report (pdf; December 2025) 

News Release

  • Delaware River Basin Commission Evaluates Sea Level Rise and Salinity in the Delaware River (issued January 15, 2026)

 
Webinar Scheduled

The DRBC has scheduled a webinar for January 27, 2026, from 12 p.m. to 1 p.m., to review the report and answer questions. 

  • Register for the webinar

Background

The Delaware River Estuary includes the tidal Delaware River and the Delaware Bay. It is undammed to the ocean, allowing for the mixing of saltwater and freshwater. Importantly, key water intakes in the estuary provide drinking water to over 1.3 million people in Philadelphia, Southeastern Pennsylvania and South Jersey.

Salinity intrusion in the estuary is tracked and managed by the DRBC using an indicator known as the salt front. The salt front is the location in the river where the water is no longer considered freshwater. While its location normally shifts due to tides and hydrologic conditions, its average location is around Wilmington, Del.

Higher tides and low flows increase salinity in the estuary and move the salt front upstream. During dry conditions, DRBC releases water from reservoirs to ensure the salt front stays in its average location, keeping salt water out of key drinking water, industrial and thermoelectric intakes.

Sea levels in the basin are rising and are expected to continue to rise in the future. As the DRBC is tasked with ensuring a sustainable supply of suitable quality water to support humans and aquatic life, it is important to understand how increased sea level rise will impact salinity levels and the location of the salt front in the Delaware River Estuary.

Using sophisticated modeling, this report examines how salinity will increase and the location of the salt front will move in the estuary at various sea level rise and hydrologic scenarios. 

Analytical Approach

The DRBC developed a 3-D hydrodynamic salinity model to determine how various levels of sea level rise would impact the salt front's location in the Delaware River Estuary under various flow conditions.  

• Sea Level Rise Scenarios: 0m; 0.3m; 0.5m; 0.8m; 1m; and 1.6m
  
  
• Modeled years of varying flow conditions (wet, dry and normal years): 1965; 2001; 2002; 2011; 2012; 2013; 2016; 2017; 2018; and 2019
  
  
• Other factors examined include impacts of marshland, dredging, ocean surface temperature and other salinity sources (e.g., from non-tidal waters)

Key Findings

• Sea level rise increases tidal water levels throughout the Delaware Estuary, amplifying tidal elevations upstream to Trenton and increasing salinity throughout the estuary. The largest increases in salinity will be seen between Chester, Pa., and the Delaware Memorial Bridge.
  
  
• Collectively, the results indicate that as sea levels rise, the maximum salt front location is further upstream regardless of the flow condition.
  
  
  • The salt front moves further upstream in drier conditions and with increased sea level rise.
    
    
  • This shows that with increased sea level rise (at 0.5 m and above) and in very dry conditions, our current flow management plan may not be effective to repel the salt front. More freshwater may be needed.
    
    
• Releasing extra pulses of water larger than current flow management requirements may help temporarily by pushing the salt front downstream.
  
  
• The effectiveness of reservoir releases depends on where the salt front is relative to the Schuylkill River confluence.  
  
  
  • If the salt front is more than a few miles above the Schuylkill River confluence, releases from reservoirs that enter the Delaware River are more effective in repelling salinity than additional water released to the Schuylkill River.
    
    
  • Releases to the Schuylkill River are more effective than releases to the Delaware River when the salt front is below or near the confluence of the Schuylkill and Delaware Rivers.

Next Steps

• The results of this study demonstrate the need to consider sea level rise in future planning and policy efforts related to flow and drought management, as well as water availability and water supply sustainability.
  
  
• The model will be refined periodically based on new data and other information.
  
  
• The DRBC Advisory Committee on Climate Change, along with other stakeholders, will be engaged to determine appropriate scenarios for future planning efforts.

Additional Resources

• Salt Front Information
  
  
• Flow and Drought Management
  
  
• Evaluation of Additional Storage in the Delaware River Basin
  
  
• Flood Mitigation Efforts
  
  
• Water Resources Resilience Plan