2C - Impact of Human Factors
Humans disrupt the drainage basin cycle by accelerating processes, (deforestation, changing land use) and creating new water storage reservoirs or by abstracting water.
It is mainly human changes to:
- rivers and drainage
- the character of the ground surface (its shape, texture and covering)
River Management
- Construction of storage reservoirs holds back river flows
- Abstraction of water for domestic flow and industrial use reduces river flows
- Abstraction of groundwater for irrigation lowers water tables
- Clearance of trees reduces evapotranspiration, but increases infiltration and surface runoff
- Arable to pastoral: compaction of soil by livestock increases overland flow
- Pastoral to arable: ploughing increases infiltration by loosening and aerating the soil
- Urban surfaces (tarmac, tiles, concrete) speed surface runoff by reducing percolation and infiltration
- Drains deliver rainfall more quickly to streams and rivers, increasing chances of flooding.
The components of the drainage basin most affected by humans are:
- evaporation and evapotranspiration
- interception
- infiltration
- groundwater
- surface runoff
Amazonia
The Amazon basin contains the world's largest area of tropical rainforest. Deforestation has disrupted the drainage basin cycle in a number of ways, including:
- A lowering of humidities
- Less precipitation
- More surface run off and infiltration
- More evaporation, less transpiration
- More soil erosion and silt being fed into rivers.