The central and southern districts are drained by the Derwent from Lake St Clair - its tributaries being the Nive, Dee, Clyde, Ouse and Jordan.
Taking a stand near Lake Fergus, to the east of Lake St Clair, the observer will find himself nearly in the centre of an extensive plateau, with an elevation, especially on the northern side, of between three and five thousand feet above the sea-level.
At its greatest elevation it is comparatively level, and contains many extensive freshwater basins, such as Lake Augusta, Lake St Clair, Lake Sorell, Lake Echo, Lake Crescent, Arthur's Lake and the Great Lake.
From the outlet of Lake St Clair and 18 m.
The water is pumped from Lake St Clair and is of exceptional purity.