Lehigh River Water Quality Monitoring

Real-time Lehigh River Water Quality Data

Courtesy of Matt MacConnell, the Lehigh River Stocking Association, and Lehigh Valley Sierra Club

The Lehigh River Stocking Association collaborates with Lehigh Valley Sierra Club to monitor water quality in the Lehigh River using submerged probes placed at various sites. Real-time depth, pH, dissolved oxygenspecific conductance, and water temperature data are accessible at the following links: https://bit.ly/LR_Data and https://bit.ly/LR_Data_2The Lehigh River Stocking Association is a local nonprofit organization dedicated to the restoration and restocking of the Lehigh River. Also a local nonprofit organization, the Lehigh Valley Sierra Club is part of the Sierra Club Pennsylvania Chapter, whose mission is to explore, enjoy, and protect the planet.

Reading the Data:

  • Depth = depth of water at the probe site, recorded in feet (ft.)
  • pH = acidity of the water at the probe site (less than 7.0 = acidic; above 7.0 = basic)
  • Dissolved oxygen (DO) = percent of oxygen dissolved in the water at the probe site (higher percentage = more DO)
  • Specific conductance = a measure of dissolved solids in the water at the probe site, recorded in microsiemens (μS) (higher specific conductance = more dissolved solids/possible pollutants)
  • Temperature = temperature of the water at the probe site, recorded in degrees Fahrenheit (F)

Sample Datasets:

Data and interpretation provided by Matt MacConnell of the Lehigh River Stocking Association

The graph above illustrates that, when river depth increases, specific conductance decreases. This general trend is supported by the understanding that rain water is nearly pure and therefore dilutes the specific conductance (dissolved solids) in the river water. This is counterintuitive to most folks because the river becomes turbid (brown) during high water, and most would assume it is more contaminated. However, this increased turbidity is caused by suspended solids, not dissolved solids. What we need to watch for in this trend is if we see depth and conductance increase at the same time. This would indicate that solutes are being washed into the river by the rain. And if conductance increases without any change in depth, we know that someone has likely dumped something into the river.

The second graph illustrates that dissolved oxygen, temperature, and pH all peak and fall at the same cyclic timing. This trend is caused by the process of photosynthesis. As river algae consume carbon dioxide from the river, they reduce the carbonic acid in the water, therefore raising the pH, while concomitantly liberating 100% pure oxygen. Observe that this trend begins at 8 a.m. and peaks at 4 p.m., aligning with daylight hours. Also observe that the percent saturation of dissolved oxygen can exceed 100%. This is due to the fact that photosynthesis produces pure oxygen (not 20.9% as in the air), and it can consequently drive the oxygen concentration of the water well above 100% saturation (in this graph, some peaks reach about 113%). On days with small pH cycles, observe that the river does not warm up as much, indicating that the day was likely overcast. When river levels rise and turbidity increases, photosynthesis is depressed.   What we need to watch for in this trend is if we see pH increase or decrease during evening hours. Since this change cannot be explained by photosynthesis, it can be attributed to human factors.