Conductivity outside this range could indicate that the water is not suitable for certain species of fish or macroinvertebrates. Considerations Conductivity is useful as a general measure of stream water quality. Each stream tends to have a relatively constant range of conductivity that, once established, can be used as a baseline for comparison with regular conductivity measurements. Significant changes in conductivity could then be an indicator that a discharge or some other source of pollution has entered a stream. Conductivity is measured with a probe and a meter.
Voltage is applied between two electrodes in a probe immersed in the sample water.
The drop in voltage caused by the resistance of the water is used to calculate the conductivity per centimeter. The meter converts the probe measurement to micromhos per centimeter and displays the result for the user. Some conductivity meters can also be used to test for total dissolved solids and salinity. Meters in this price range should also measure temperature and automatically compensate for temperature in the conductivity reading. Conductivity can be measured in the field or the lab.