The Water Cycle
Learn about the water cycle
The natural water cycle refers to the movement of water between the Earth’s surface and atmosphere through four processes:
- evaporation: liquid water evaporates from soils, oceans, lakes and water surfaces to becomes water vapour
- transpiration: Plants absorb water through their roots and release it as vapour through their leaves. Forests produce water vapour.
- precipitation: water falls from the atmosphere back to earth as rain, hail, or snow
- condensation: water vapour turns back into liquid when the temperature drops. This process produces clouds, morning dew, and the liquid on the outside of a cold drink.
Shallow aquifers may be involved in the shorter term water cycle. Recharged by water soaking through soils, they may release water through springs or into rivers & lakes. Coastal aquifers may interact with the ocean.
Learn more about the water cycle in this great fact sheet (from South East Water), and this interactive website (Unity Water).
Human activities impact the water cycle
- Water supply services can interrupt the natural water cycle by removing water from one place and moving it to another location as wastewater. For example, the current Rous system relocates water from the Rocky Creek catchment. This is piped via the reticulation and then sewerage system to the coastal plain at Byron Bay. Although Byron Shire does an excellent job treating and then cleaning this water in wetlands created for this purpose, excess water in that location causes problems with the water table.
- The removal of plants and forests impacts the water cycle:
- With less vegetation, we reduce transpiration, the way plants move water from the soil into the air. The Rous region was once covered with subtropical rainforest, but only 1% of the Big Scrub remains (some of this would be destroyed if Dunoon Dam were to proceed).
- When we destroy trees and forests, we reduce vapour in the air and potential cloud formation.
- Plants and vegetation slow down water when it moves across landscapes. The removal of plants & vegetation increases the speed of flash flooding. Planting and preserving vegetation can prevent flash flooding. This concept forms the basis of the Northern Rivers Watershed Initiative to revegetate the Richmond River catchment.
- Buildings and roads create an impermeable cover that stops water from being absorbed by soil. This can lead to flash flooding in heavy rain. Runoff can also contain polluting chemicals.
- The release of carbon dioxide and other greenhouse gases into the atmosphere causes global temperature to rise. This changes the water cycle because the processes of evaporation, transpiration, condensation, and precipitation are all driven by temperature. Rainfall is decreasing in southern Australia and becoming unpredictable.
- Irrigation and agriculture are consistently the biggest water users in Australia, according to the Australian Government’s State of the Environment reporting. While it’s important that farmers have enough water to grow crops and feed animals, it’s equally important that water resources and ecosystems are protected to ensure sustainable access long into the future.