water cycle: key topic one

Question 1

What is the global hydrological system?

Answer 1

the circulation of water around the earth

Question 2

What type of system is the hydrological system?

Answer 2

a closed system of linked processes so there are no external inputs or outputs
-> the amount of global water is finite and constant

Question 3

Where does the power that drives the global hydrological cycle come from?

Answer 3

• solar energy (form of heat)
• gravitational potential energy (causes rivers to flow downhill and precipitation to fall to the ground)

Question 4

What are the four main stores in the water cycle?

Answer 4

• the oceans
• glaciers and ice sheets
• surface runoff (rivers, lakes, groundwater and the moisture held in soils and vegetation)
• the atmosphere

Question 5

How much water is stored in each of the freshwater stores?

Answer 5

• the cryosphere = 69%
• groundwater = 30%
• biosphere (vegetation and soil moisture) = <1%

Question 6

What is a flow?

Answer 6

the transfers of water from one store to another

Question 7

What is the amount of flow of water between the oceans and atmosphere?

Answer 7

evaporation = 400,000 km^3 per year
precipitation = 370,000 km^3 per year

Question 8

What is the amount of flow of water between the atmosphere and landmasses?

Answer 8

evaporation = 60,000 km^3 per year
precipitation = 90,000 km^3 per year

Question 9

What is the amount of flow of water between the landmasses and oceans?

Answer 9

surface runoff = 30,000 km^3 per year

Question 10

What is a flux?

Answer 10

the rates of flow between stores

Question 11

Where do the greatest fluxes take place?

Answer 11

over the oceans

Question 12

What is the global water budget?

Answer 12

takes into account all the water that is held in stores and flows of the global hydrological cycle

Question 13

How much of the global water budget is freshwater?

Answer 13

2.5%

Question 14

How much freshwater is ‘easily accessible freshwater’?

Answer 14

only 1%

Question 15

Where is 70% of freshwater locked up?

Answer 15

glaciers and ice sheets

Question 16

What is residence time?

Answer 16

the average time a molecule of water will spend in one of the stores

Question 17

What is the average residence time in the atmosphere?

Answer 17

10 days

Question 18

What is the average residence time in the ocean?

Answer 18

3600 years

Question 19

What is the average residence time in ice caps?

Answer 19

15,000 years

Question 20

What two water stores are claimed to be non-renewable?

Answer 20

• fossil water (ancient, deep groundwater made from pluvial (wetter) periods in the geological past)
• the cryosphere (Made up of those areas of the world where water is frozen into snow or ice)

Question 21

What is the most critical feature of the global water budget from a human viewpoint?

Answer 21

accessible surface water is only 1% of all the worlds freshwater, and this is the major source of water for human use