Studies in Australian Estuarine Hydrology. II. The Swan River

Abstract

The physiography of the Swan River is described, with particular reference to the drowned valley basin which is connected to the sea across a shallow sill. The climatological features of the region are discussed, together with the tidal characteristics of the basin. Drought conditions prevail during the summer, effective rainfall being confined to the winter months. Density stratification in the basin is intense and prolonged, because of the weakly developed tidal mixing.

Changes in the mean water level of the basin are correlated with variations in barometric pressure; the amplitude of these changes sometimes exceeds that of the lunar tides. This fact has a significant bearing on hydrological conditions within the basin.

The distribution and the seasonal cycles of temperature, chlorinity, and oxygen saturation are compared with those of a tidal-dominated estuary situated at the same latitude In eastern Australia. Most of the differences in these cycles can be attributed to the tidal regimes of the two systems.

Nutrient cycles within the Swan River basin are discussed with particular reference to the recovery period following the development of stratification. In the later stages of the investigation this period was studied intensively, and from the information obtained several theories are advanced to explain the circulatory features of the basin region.

An attempt is made to classify the Swan River estuary.