The presence of charged ionic species in solution enables water to conduct an electrical current. This is referred to as conductivity, electrical conductivity (EC) or conductance, and it is directly related to the total dissolved salt concentration. Conductivity is best measured in the field using an electronic probe that applies a voltage between two electrodes. EC is sensitive to water temperature. The international standard temperature for laboratory conductivity measurements is 25 oC. Most modern field instrumentation will correct and standardise conductivity readings to this temperature and then refer to the measurement as specific conductance. It is worth mentioning that different standard temperatures were used in the past, so the water temperature at which the measurement was taken should always be reported. Up until around the late 1970s the units of EC were micromhos per centimetre (?mhos cm-2) after which they were changed to microSiemens cm-2 (1?S cm-1 = 1 ?mho cm-1).

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