The water cycle, also called the hydrological cycle, refers to the movements of water between the atmosphere, lithosphere and biosphere. The hydrological cycle can be viewed as a closed system, as no water is lost from the system. However, if the water cycle is being looked at within a single drainage basin then it can be viewed as an open system. This cycle is made up of a number of inputs, outputs, stores and transfers.
How can humans influence the hydrological cycle?
There are many human impacts on the hydrological cycle, such as:
- Deforestation: This is when humans cut down trees. If there are less trees then less interception can take place. This means that more precipitation falls directly onto the surface increasing the amount of surface run-off. Deforestation tends to increase the risk of flooding because water reaches the ground and rivers quicker, causing the ground to become saturated and rivers to flood.
- Urbanisation and construction: When houses and roads are built, more impermeable surfaces are created meaning that there is less infiltration and more surface run-off. However, buildings can also intercept precipitation and humans can build artificial drains which can reduce flooding by redirecting water away from vulnerable areas.
- Afforestation: Afforestation is the opposite of deforestation, it is when humans plant trees, the amount of interception increases. This means that water reaches the ground more slowly and can reduce flooding because it takes longer for precipitation to reach the ground and ultimately the river, meaning that the ground has time to absorb any excess water through infiltration.
- Dams: Dams create artificial surface stores (reservoirs). They are also used to regulate the discharge and velocity of the river, meaning that they can reduce the risk of flooding.
- Deforestation: This is when humans cut down trees. If there are less trees then less interception can take place. This means that more precipitation falls directly onto the surface increasing the amount of surface run-off. Deforestation tends to increase the risk of flooding because water reaches the ground and rivers quicker, causing the ground to become saturated and rivers to flood.
- Urbanisation and construction: When houses and roads are built, more impermeable surfaces are created meaning that there is less infiltration and more surface run-off. However, buildings can also intercept precipitation and humans can build artificial drains which can reduce flooding by redirecting water away from vulnerable areas.
- Afforestation: Afforestation is the opposite of deforestation, it is when humans plant trees, the amount of interception increases. This means that water reaches the ground more slowly and can reduce flooding because it takes longer for precipitation to reach the ground and ultimately the river, meaning that the ground has time to absorb any excess water through infiltration.
- Dams: Dams create artificial surface stores (reservoirs). They are also used to regulate the discharge and velocity of the river, meaning that they can reduce the risk of flooding.
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