water cycle: key topic one Flashcards
(21 cards)
What is the global hydrological system?
the circulation of water around the earth
What type of system is the hydrological system?
a closed system of linked processes so there are no external inputs or outputs
-> the amount of global water is finite and constant
Where does the power that drives the global hydrological cycle come from?
- solar energy (form of heat)
- gravitational potential energy (causes rivers to flow downhill and precipitation to fall to the ground)
What are the four main stores in the water cycle?
- the oceans
- glaciers and ice sheets
- surface runoff (rivers, lakes, groundwater and the moisture held in soils and vegetation)
- the atmosphere
How much water is stored in each of the freshwater stores?
- the cryosphere = 69%
- groundwater = 30%
- biosphere (vegetation and soil moisture) = <1%
What is a flow?
the transfers of water from one store to another
What is the amount of flow of water between the oceans and atmosphere?
evaporation = 400,000 km^3 per year
precipitation = 370,000 km^3 per year
What is the amount of flow of water between the atmosphere and landmasses?
evaporation = 60,000 km^3 per year
precipitation = 90,000 km^3 per year
What is the amount of flow of water between the landmasses and oceans?
surface runoff = 30,000 km^3 per year
What is a flux?
the rates of flow between stores
Where do the greatest fluxes take place?
over the oceans
What is the global water budget?
takes into account all the water that is held in stores and flows of the global hydrological cycle
How much of the global water budget is freshwater?
2.5%
How much freshwater is ‘easily accessible freshwater’?
only 1%
Where is 70% of freshwater locked up?
glaciers and ice sheets
What is residence time?
the average time a molecule of water will spend in one of the stores
What is the average residence time in the atmosphere?
10 days
What is the average residence time in the ocean?
3600 years
What is the average residence time in ice caps?
15,000 years
What two water stores are claimed to be non-renewable?
- 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)
What is the most critical feature of the global water budget from a human viewpoint?
accessible surface water is only 1% of all the worlds freshwater, and this is the major source of water for human use
