4.1 the hydrological cycle

Question 1

% of the earth covered by water

Answer 1

70%

Question 2

% of water that is fresh

Answer 2

2.6%

Question 3

the life of a water molecule

Answer 3

• water on earth = constantly cycled
• size of storages in cycle = long time for water molecule to flow from one storage to another
• water can be both renewable and non-renewable (atmosphere + rivers = renewable –> oceans + ice-caps = non-renewable)

Question 4

stores of water

Answer 4

• oceans - 97% of earth’s water
• ice-caps/glaciers - 2% of earth’s water
• groundwater - 0.2% of earth’s water
• lakes/rivers - 0.02% of earth’s water
• atmosphere - water vapour

Question 5

transfers “flows” of water

Answer 5

• ocean conveyer belt
• surface runoff - flow of water along surface after heavy rain
• infiltration - soaking of water in porous soils

Question 6

ocean circulation and climate

Answer 6

• water = high heat capacity –> can absorb heat energy from equatorial regions + transport it towards the poles
• evens out world’s climate
• e.g: heat transported by gulf stream maintains western europe’s mild climate

Question 7

transformation of water

Answer 7

• evaporation - liquid water → water vapour
• condensation - water vapour → liquid water (cloud formation)
• freezing / melting

Question 8

powering global hydrological cycle

Answer 8

powered by solar radiation –> drives endothermic transformations of water

Question 9

human impacts on hydrological cycle

Answer 9

• extraction of water for agricultural, industrial, and domestic use
• discharges –> contains pollution (e.g. sewage, pesticide run-off)

Question 10

flash flooding

Answer 10

• climate change increases probability of heavy precipitation
• land clearance for agriculture –> water absorbed less effectively
• deforestation increases rate of runoff –> tree leaves intercept falling precipitation