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Water Quality

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Water Quality

The graphs below are created using an automated process. Each night, scripts retrieve data via the internet and process information to update the graphs. Disruptions to data feed, internet service, and other events beyond the control of DRBC could delay update of the graphs.


Healthy concentrations of dissolved oxygen in water are critical to the support of aquatic life. The dissolved oxygen plot retrieves the daily 24-hour mean dissolved oxygen concentrations from each of the last five days from continuous real-time USGS water quality monitors at Trenton, Pennypack Woods, the Ben Franklin Bridge, Chester, and Reedy Island, and compares these values to the DRBC water quality standards for dissolved oxygen. For each location, the largest, darkest dot is the most recent daily mean, and the lightest smallest dot is the oldest, showing the trend for the last five days. For dissolved oxygen, the desired condition is a concentration that is higher than the standard (above the red line). When a dot is below the red line, this indicates a potential violation of the DRBC water quality standards for dissolved oxygen. River Mile is the distance in miles upstream from the line between the Cape May Light (New Jersey) and the tip of Cape Henlopen (Delaware), where Delaware Bay meets the Atlantic Ocean.

This plot compares all the continuous temperature data collected at both NOAA PORTS and USGS NWIS stations to the DRBC temperature criteria. NOAA PORTS temperature observations are typically reported every hour, while NWIS observation reporting intervals range from every 15 minutes to every hour, depending on the location. In Zones 2, 3, and 4, DRBC's temperature criteria changes for each day of the year, as described in the DRBC water quality regulations. When an observation (circle) is above the line, this indicates a potential violation of the DRBC water quality standard for temperature. River Mile is the distance in miles upstream from the line between the Cape May Light (New Jersey) and the tip of Cape Henlopen (Delaware), where Delaware Bay meets the Atlantic Ocean.

Total Dissolved Solids (TDS) is a measure of the combined content of material in water that can pass through a filter and remains after drying in an oven. TDS in freshwater is an important water quality indicator for protection of both drinking water and aquatic life. DRBC has established a surface water quality standard for TDS of 500 mg/L in freshwater zones of the Delaware River. Although TDS can only be measured in a laboratory, it is closely correlated with Specific Conductance, which can be measured in near real-time using in-situ instruments. The plot above uses near real-time specific conductance data reported by the USGS and paired measurements of specific conductance and TDS to estimate the current TDS concentrations in the Delaware River. In the plot, we use paired measurements from the Boat Run monitoring program for the estuary, and paired measurements from the Scenic Rivers Monitoring Program for the non-tidal River. River Mile is the distance in miles upstream from the line between the Cape May Light (New Jersey) and the tip of Cape Henlopen (Delaware), where Delaware Bay meets the Atlantic Ocean.

Chloride and sodium are both measures of salt. DRBC has established surface water quality standards for chloride and sodium in the tidal freshwater zones of the Delaware Estuary. Maintaining freshwater in that portion of the estuary is important for protecting drinking water withdrawn from that part of the river and for protecting aquatic life. Although chloride and sodium are typically measured in a laboratory, they are closely correlated with Specific Conductance, which can be measured in near real-time using in-situ instruments. The plots above use near real-time specific conductance data reported by the USGS and regression relationships from DRBC's Delaware Estuary Water Quality Monitoring to estimate chloride and sodium and compare to criteria. River Mile is the distance in miles upstream from the line between the Cape May Light (New Jersey) and the tip of Cape Henlopen (Delaware), where Delaware Bay meets the Atlantic Ocean.


R scripts developed by John Yagecic. HTML programming by Karl Heinicke. Questions, contact John.Yagecic@drbc.nj.gov