Relationship between conductivity and analysed composition in a large set of natural surface-water samples, Queensland, Australia

The relationship between Total Dissolved Ions (TDI) and conductivity is established in around 34000 samples collected from rivers, streams and dams in Queensland since the 1960s. These data are extremely variable in content, reliability and periodicity of sampling. The data were sorted into useable modules, and their statistical distribution was examined. The median ratios of TDI/Conductivity obtained for different salinity ranges were between 0.59 and 0.72, with normal variability ranging from below 0.35 to greater than 1.00, particularly at lower salinities. The data set used has sufficient sample numbers and areal distribution per increment to give reasonable reliability within the conductivity range of 50–1000 μScm –1 . A table has been developed that enables selection of conversion factors from conductivity to salinity (as TDI) which could be used to predict TDI from future conductivity measurements from the same surface water population.