Rainfall
The potential hydro power output of an area is related to the amount of snow and rain received in that area. For this reason Tasmania's dams and power stations have been built in high rainfall areas or on rivers running from these areas.
Run-offs
The proportion of rainfall that runs off into streams depends on a variety of factors including the shape of the land surface, the amount of rainfall and the types of soil and vegetation. The percentage of run-off can be as low as 20 per cent in dry areas and above 80 percent in wetter areas such as the West Coast.
Catchment Areas
The volume of rainfall that will run off into a proposed storage is dependent upon the area of land surrounding and sloping towards that storage. This area of land is known as the catchment area. See Tasmania's catchment areas.