RAINFALL AND SALINITY

The annual means of rainfall, taken over 15 - 17 years, and of salinity over available intermittent years display a lowering of salinity in the Gulf of Carpentaria and along Queensland's northern shore beyond Townsville (TL). The higher salinities in the Great Australian Bight between Thevenard (TV) and Victor Harbor (VH) are probably associated with evaporation and the width of the continental shelf. The low values around Cape York Peninsula are due to heavy rainfall during the monsoon season, large catchments and runoff.

The most striking feature of the correlation of the monthly means of rainfall and of salinity is the correlation of the two parameters in the Cape York region. The dilution of the sea water by rain there is so great that its relationship to changes in the mean sea levels, with respect to geodetic levels, observed some years ago between Brisbane (BB) and Cape York (BA) deserves investigation. The catchment aspect of this dilution process and the fact that all tide gauges in the area are located on rivers or near their mouths may help to explain this phenomenon.

Despite the doubtful nature of the salinity averages of larger or smaller, non-synoptic numbers of measurements, the correlation between the curves of the monthly variations at different stations is reassuring. The lack of rain along the shore of the Great Australian Bight and the heavier rainfall of the South-West are accompanied by smaller and larger overall monthly variations, respectively. The previously referred to mean sea level survey also divulged an increase in the discrepancy between geodetic and mean sea levels around the South-West.