Teacher background information
What is a catchment area?
A catchment area is an expanse of land that intercepts water and then flows to a certain point either on the surface or underground. It might include a lake, a reservoir (or dam), a stream or any other water body and areas where water soaks into the ground and recharges as groundwater.
The school is a catchment area that may involve two or three sub-catchments (e.g. a car park, basketball court, school oval, gardens).
Rainfall seeps through soil into the water table, where it collects in groundwater aquifers. Pollutants spilled on the ground, or leaking from storage vessels, have the potential to contaminate groundwater aquifers through seepage. Groundwater contamination in the shallow aquifer system can endanger community health and threaten the environment, especially the fauna and flora of wetlands.
What are drainage systems?
Drainage systems consist of pipes or open-channel drains that transport stormwater runoff and groundwater to natural water bodies such as rivers, wetlands or the ocean or to compensating basins. They often follow the route of natural watercourses that existed before any land development or clearing took place.
Drainage systems prevent flooding of developed land from surface runoff and from rising groundwater levels. In areas of high water tables, drainage systems lower the groundwater level so that the land can be developed.
Stormwater is not treated and in some cases, leads directly to our water bodies such as rivers, lakes, wetlands or the ocean. The water also seeps into the ground and is taken up by plants, evaporates or gradually trickles down into the groundwater. Stormwater runoff easily collects pollutants along its path.
There are many ways in which human activity can impact on water draining from a catchment. These include:
- dumping of oil, paint and solvents
- dog waste
- waste from industrial areas
- domestic fertiliser run-off
- oil and fuel from cars.