Salinity can be measured using electrical conductivity
(E.C.) because there is a strong relationship between E.C. and the concentration
of salt in water. The advantage of using E.C. as a measure of salinity is that
E.C. can be recorded continuously, unlike spot samples analysed in a
laboratory. E.C. is measured in micro-siemens per centimetre.
The relationship between E.C. and salt concentration changes
with water temperature, so E.C. values are usually ‘corrected’ to represent
E.C. at 25 degrees Celsius. This makes it possible to compare salinity at
different sites or at the same site over time.
While there are currently no standards for calculating
corrected E.C., most agencies in Australia adopt a rule of thumb where E.C. is
increased 2% for each degree below 25 degrees Celsius. This formula is an
approximation as the relationship will change depending on other factors, such
as the composition of the salts being measured.
