This guide has information on surface water, including climatic zones, drainage divisions and uses in the Northern Territory.
Water moves between oceans, the atmosphere and the land. Water that is seen on the surface, either flowing or stored in natural depressions like lakes and waterholes, is called surface water.
Most surface water comes from rainfall runoff from the surrounding land area or catchment.
There are three types of surface water:
- Permanent or perennial surface water is always present as rivers, lakes, springs and swamps - these are supported by groundwater when there is little or no rain.
- Semi-permanent surface water holds water for part of the year and are usually small creeks, lagoons, waterholes or low lying areas in the arid zone.
- Man-made surface water can be held in man-made structures ranging from lakes, dams and turkey nests to artificial swamps and sewage treatment ponds.
The Wet and Dry seasons cause great changes in surface water.
Most surface water is found in the Top End where the tropical climate brings large quantities of rain and high humidity.
Surface water in the arid zone is minimal due to much lower rainfall.
Clay pans, salt pans, rivers and flood outs are dry most of the time, but infrequent yet sometimes intense rainfall events cause arid zone streams to flow for short periods.
Surface waters are essential for life - human, plant and animal.