Changes Over Time: Human Impacts

Question 1

What are the human impacts to the water cycle over time

Answer 1

Farming practices, land use change, water abstraction

Question 2

Farming practices

Answer 2

Ploughing breaks up the surface, increasing infiltration
Arable farming can increase interception and evapotranspiration
Pastoral farming compacts soils, reducing infiltration and increasing runoff
Irrigation removes water from local rivers, decreasing their flow

Question 3

Land use changes

Answer 3

Deforestation (e.g for farming) reduces interception, evapotranspiration and but infiltration increase (dead plant material in forests usually prevents infiltration)
Construction reduces infiltration and evapotranspiration, but increases runoff Irrigation removes

Question 4

Water abstraction (water removed from stores for human uses)

Answer 4

This reduces the volume of water in surface stores (e.g lakes)
Water abstraction increases in dry seasons (e.g water is needed for irrigation)
Human abstraction from aquifers as an output to meet water demands is often greater than inputs to the aquifer,
Leading to a decline in global long term water stores