Water EQ1 - Hydrological cycle Flashcards
What is the global hydrological cycle?
A closed system of never ending water circulation driven by solar energy and gravitational potential energy
What is a store?
Reservoirs where water is held e.g. the ocean
What is a flux?
The rate of flow between stores
What is a process?
The physical mechanisms which drive the fluxes of water between the stores
What is the cryosphere?
Areas of the Earth where water is frozen into snow or ice
What is blue water?
Water stored in rivers, streams, lakes and groundwater in liquid form (visible part of the hydrological cycle)
What is green water?
Water stored in the soil and vegetation (invisible part of hydrological cycle)
What are the main global water stores?
Oceans, atmosphere, biosphere, cryosphere, groundwater, surface water
Which are the largest stores?
Oceans and icecaps
What is residence time?
The average time a water molecule spends in a reservoir or store
Which stores have the longest/shortest residence times?
Longer = cryosphere (up to 800,000 years), groundwater (10,000 years)
Shorter = surface water, atmospheric water (about ten days)
What is fossil water?
Ancient groundwater formed as the result of former pluvial periods. Not renewable or reachable for human use
What is precipitation?
The movement of water in any form from the atmosphere to the ground
What is evaporation?
The change in state of water from a liquid to a gas
What is transpiration?
The diffusion of water from vegetation to the atmosphere, involving a change from a liquid to a gas
What is groundwater flow?
The slow transfer of percolated water underground through pervious (permeable) or porous rocks
How much water is available to humans?
Only 2.5% of Earth’s water is freshwater, and 69% of this is locked up in the cryosphere, whilst 30% occurs as inaccessible groundwater. This leaves only 1% of fresh water easily accessible for human use
What store has the longest/shortest residence time?
Ice sheets (800,000 to 1 million years) and groundwater (10,000 years) have the longest. Atmospheric moisture is the shortest (about ten days)
Why is the hydrological cycle a closed system?
There are no external inputs or outputs
What is a drainage basin?
Subsystem within global hydrological cycle, the area of land drained by a river and its tributaries
Why is a drainage basin an open system?
Has external inputs and outputs that cause the amount of water in the basin to vary over time
What is a watershed?
The highland which divides and separates waters flowing to different rivers
What conditions are needed to form precipitation?
- air cooled to a saturation point with relative humidity of 100%
- condensation nuclei
- temperature below dew point
What is condensation?
The change from a gas to a liquid
What is dew point?
The temperature at which dew forms, measure of atmospheric moisture