The Water Cycle
Did you know?
The overall amount of water on earth has remained the same for 2 billion years and the only thing that changes is how this water is distributed
You could be drinking the same water as a dinosaur did, 100 million years ago
Every living thing on earth including us, is part of the earth’s water cycle. Water moves in an endless cycle from the sea and land to the atmosphere and back again
The sun’s energy converts water from oceans, rivers, lakes and surface layers of soil into water vapour through evaporation.
Importantly, plants also add water vapour through transpiration.
The water vapour rises into the atmosphere and condenses into clouds and then precipitates and falls back to the land or sea as rain, sleet, hail or snow.
Most of the rain that falls on land either soaks into the soil in a process called infiltration or runs off the land surface into rivers, lakes and eventually out to the sea.
People have changed the natural water cycle, building pipes that take water for drinking and remove sewage and storm water.
This is the called urban water cycle.
Catchments to tap
When it rains, the run-off flows into rivers and onto dams and reservoirs and water mains that make up our water supply system, then making its way to us to use and look after.
Toilets to sewage plants
Used water from homes and businesses travels through sewer pipes to sewage treatment plants. These plants remove toxic substances and treated water is pumped back into the natural water cycle, or recycled on farms, parks and golf courses.
Stormwater drains collect rainwater run-off from roads, roofs and gutters, and send it into nearby rivers and creeks. These eventually carry the water into our bays and the ocean, where it re-enters the water cycle. It’s so important to ensure that stormwater is free of litter and pollutants and as clean as possible.
When rain falls, some of it flows across the surface of the land and accumulates in rivers, lakes, and eventually the ocean. But some of the water seeps into the ground and accumulates within cracks or pores in the rocks (aquifers), forming groundwater resources, which in turn also eventually flow into rivers, lakes or the ocean.
In Australia, groundwater makes up approximately 17 per cent of accessible water resources and accounts for over 30 per cent of our total water consumption. Some groundwater is fresh and can be used for drinking. Other groundwater can be brackish water or even saltier than the sea. Some contain high levels of dissolved chemicals, rendering it unsuitable for human consumption or stock water supplies.
Approximately 2 per cent of the Earth’s water occurs as groundwater, compared with 0.1 per cent as rivers and lakes and 94 per cent as oceans.