Merrimack River: Long Term Data

The Merrimack River Watershed Council has deployed four temperature and conductivity probes to collect data for a year to analyze trends in temperature change that may be related to road salt runoff or climate change. Probes take two readings a day, one at noon and one at midnight. The probes are in Tyngsboro Massachusetts, Merrimack New Hampshire, Manchester New Hampshire, and Milford New Hampshire to measure long term temperature data. The following graphs show data from the first weeks of activation.

What Does This Mean?

“Conductivity is a measure of the ability of water to pass an electrical current”. Increased saltiness can increase the conductivity of water so that could be an indicator of road salt runoff into the river. Conductivity can be affected by temperature because warmer water carries a higher conductivity. The conductivity of rivers in the United States ranges from 50 to 1500 µm/cm. Streams supporting good mixed fisheries have a range between 150 and 500 µm/cm. Higher or lower conductivity could indicate that the water is not suitable for certain aquatic species. Significant changes in conductivity could indicate runoff or some other source of pollution.

Temperature can alter water density and the solubility of oxygen and other chemicals. Fluctuating temperatures and extreme temperatures could be stressful to aquatic life.

Definitions derived from

This grant is funded by the New Hampshire Charitable Foundation and The Agape Foundation.


GPS coordinates for this site are 42°51.580 N and 71°29.601 W


GPS coordinates for this site are 42°50.548 N and 71°42.338 W


The GPS coordinates for this site are 42°51.740 N and 71°29.563 W. This site is located below the Manchester airport to gather data from road salt runoff from the planes and heavy traffic.


This site is located below the Pheasant Lane Mall to gather data from road salt runoff from cars.