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A Guide to Understanding MWA's Latest Sensors

MWA has received a grant to place sensors at sites where we would like to understand how managing levels in headwater lakes influences river health. Our sensor stations are SL101 and SL102.  SL101 is at Old Waterloo Road in Stanhope, NJ and is downstream of Lake Musconetcong.  SL102 is in Byram Township, NJ off of River Road and is downstream of the Musconetcong sewage treatment plant.  Both of these sensor location sites are located downstream of Lake Hopatcong and Lake Musconetcong.

During the summer season, the flow from Lake Hopatcong is supposed to be kept at 12 cfs (cubic feet per second) as read on the stream gage at the Lake's dam.  This rule is designed to keep Lake Hopatcong at around 8 feet deep at the dam, protect flows to the river for fishing and aquatic life, and maintain a passing flow of 6.8 cfs for the sewage treatment plant.  But there was never a gage at Lake Musconetcong making it difficult to determine how managing that lake impacts the river downstream.  Volunteers have observed that, during the summer months, the depth of water gets very shallow in sections downstream of Lake Musconetcong.  Until recently, it has not been clear how lake releases in the fall effect our watershed downstream.

MWA interpretative and sensor information sign at Riverside Park in Byram Township, NJ.

The recently installed sensors now collect continuous water depth, conductivity, turbidity and temperature.

​​Water Depth can be used to calculate discharge.  Some refer to this as "flow." Discharge is calculated by developing a graph of the relationship of depth to volume and them comparing depth measurements against this graph.  Our project partners at Stroud are working on a display to show discharge as well as depth.

Conductivity (specific conductance) is a measure of how well water in the river at the site conducts electricity.  This is an indicator of the levels of pollutants in the river.  Water depth and conductivity are displayed in the same graph.

Turbidity is the measure of water clarity, and it is an indicator of the amount of sediment in the river.

Water Temperature is displayed in degrees Celsius.  For those who are not used to thinking in Celsius, below is a guide that translates Celsius to Fahrenheit:

0°C = 32°F   water freezes; 0°C air is warm jacket weather

10°C = 50°F   perfect temperature for trout; 10°C is light jacket weather

20°C = 68°F   trout may die after capture; at 20°C, a light sweater may be needed

30°C = 86°F   fish do not survive this heat; 30°C is bathing suit weather!

Logger Temperature is the temperature inside the sensor unit.  Electronics can be effected by temperature, so we use this to determine weather the sensor is being influenced by the weather.  Water temperature and logger temperature are displayed on the same graph.

Battery is the measure of how well the solar panel on the sensor station is charging the battery.  This is used to help maintain the sensor.

Click here for a link to the gage site

MWA is excited to begin tracking readings through these sensors.  We would like to thank our friends at Stroud as well as Trout Unlimited and The Watershed Institute who were also partners on this project.  They have deployed a sensor on a tributary of the lower Musconetcong where there has been a lot of restoration work done.  Their sensor is SL116.

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