Electrical conductivity (EC)
Water that contains salt is able to conduct electricity. The more salt there is in a solution, the easier it is for and electric current to flow. The potential of a solution to pass an electric current is called electrical conductivity (EC) and it is usually measured in microSiemens per centimetre (µS/cm). This is often expressed simply as an 'EC Unit'.
As the concentration of salt in a solution increases, so does the EC reading. An EC meter can also be used to measure the amount of salt in soil by mixing a soil sample with water and then testing the EC of the solution.
The most commonly used units of measurement in NSW are 'EC Units' or 'µS/cm'.
Other units for measuring salinity are:
- deciSiemens per metre (dS/m)
- milliSiemens per centimetre (mS/cm)
- millimho per centimetre (mmho/cm)
- Parts per million in water (mg/litre)
Converting units of measurement
One unit of measurement can be converted to another by using the following information: 1000 EC (µS/cm) = 1dS/m = 1mS/cm = 1mmho/cm = 640 ppm.
|To Convert from this...||To this...||Do this|
|EC (µS/cm)||dS/m||Divide by 1000|
|dS/m||EC (µS/cm)||Multiply by 1000|
|dS/m||ppm||Multiply by 640|
The amount of salt carried in rivers, streams, groundwater or surface run-off, in a given time period, is called the salt load. The salt load is calculated from data on salinity and stream flow and is often expressed in kg/day, tonnes/day or tonnes/year.
Salt load estimates are vital because they indicate the amount of salt stored in the landscape, washed from land, or entering the system from groundwater. If we only used salt concentration (measured as EC) as an indicator of salinity, we would not have a sense of the total quantity of salt in the system. For example, if a river has high flows, salt concentration (EC) can be low, but the salt load can still be very high. Salt loads also indicate the potential rate of salt build up in places where salt might accumulate, such as wetlands and depressions on floodplains.
Salt load estimates are also important in predicting the impacts of salinity further downstream in the system.
NSW contributes a salt load of 710,000 tonnes into the Murray Rivers as it flows into South Australia. This is roughly equivalent to 1,950 tonnes of salt per day, which is like having 77 semitrailer loads of salt passing through your front door each day.
The Government and communities are reducing salt loads through actions and initiatives under the NSW Salinity Strategy and by implementing Catchment Action Plans developed for each major region by Catchment Management Authorities.
Page last updated: 26 February 2011