Conductivity is a general measure of water quality. Streams have a relatively constant range of conductivity and significant changes indicate that a discharge or other source of pollution has entered a stream. A failing sewage works would raise the conductivity because of phosphate and nitrate; while an oil spill would lower the conductivity.
Smart sensors for conductivity are relatively low cost so can be deployed in greater numbers giving higher spatial resolution over a catchment. Deployed at key points (e.g. upstream and downstream of known sources) sensors can indicate the activity of that source. Water quality sampling or the use of other sensors can then be targeted at problem sources once key areas have been identified.
Smart sensors for conductivity, temperature and depth (another useful parameter) are simple to calibrate and deploy, they require little maintenance so can be used by those with little or no experience with in situ water quality monitoring sensors.
In 2013/14, Westcountry Rivers Trust and researchers from Plymouth University deployed six INW AquiStar conductivity, temperature and pressure Smart Sensors alongside automatic water samplers along a 5km section of the Fingle Brook (a tributary of the River Teign) in order to assess the impact of contaminated road runoff from the A30 and to assess pollution loads derived from other sources in the catchment (2x sewage treatment works and historical mine works).
The data-loggers in the Fingle Brook recorded clear conductivity fluctuations that could be characterised as both flow related pollution events derived from the road surface and historic mining workings, and diurnal signatures derived from sewage effluent discharges at various locations along the watercourse.
This data allowed more detailed monitoring work to be targeted at the most likely sources and for tailored mitigation measures to be designed and implemented.