Water Cycle Flashcards
How much of the water on Earth is freshwater?
3%
What stores is the freshwater divided into?
69% in cryosphere
30% in groundwater
0.3% as liquid freshwater
0.04% as water vapour
What is groundwater?
Water stored underground in lithosphere
What is the global hydrological cycle?
Water constantly cycled between stores
What type of system is the global hydrological cycle?
Closed - no input or output of water
What does the magnitude of each store depend on?
Amount of water flowing through the store
How does evaporation affect the water cycle?
Increases amount of water stored in atmosphere
Why does the magnitude of evaporation vary by location and season?
- If there’s lots of solar radiation and a large supply of water + warm dry air, evaporation is high
- if there’s little solar radiation, small supply of water and cold damp air, evaporation will be low
When does condensation occur?
When air containing water vapour cools to its dew point
What is the dew point?
Temperature at which water vapour turns to liquid
How does condensation affect the water cycle? Give an example.
Water droplets can stay in the atmosphere or flow to other subsystems e.g. condensation = dew on leaves = less water stored in atmosphere
What is the magnitude of condensation dependent on? Give an example.
Amount of water vapour in the atmosphere
Temperature
e.g. lots of water vapour + drop in temp = high condensation
What are 2 essentials of the water cycle?
Cloud formation
Precipitation
Why is precipitation important in the water cycle?
It’s the main flow of water from atmosphere to ground
How do clouds form?
When warm air cools, causing water vapour to condense and turn into water droplets, which gather as clouds.
When they’re big enough, they fall as precipitation.
What 3 things affect cloud formation?
- Other air masses
- Topography
- Convection
How do ‘Other Air Masses’ affect cloud formation? What type of precipitation does this result in?
Warm air = less dense than cold air.
When warm air meets cold air, it’s forced above cool air, where it cools as it rises.
This results in frontal precipitation.
How does topography affect cloud formation? What type of precipitation does this result in?
Warm air is forced to rise when it meets mountains, causing it to cool.
This results in orographic precipitation.
How does convection affect cloud formation? What type of precipitation does this result in?
When sun heats ground, moisture on ground evaporates + rises.
It cools as it rises.
This results in convective precipitation?
Why can’t clouds form from water droplets alone?
Water droplets are too small - for cloud formation there need to be other tiny particles of substances e.g. soot to act as cloud condensation nuclei.
This gives water a surface on which to condense on
What 2 factors cause variation in cloud formation?
Season - in UK more rain in winter than summer
Location - Precipitation higher in tropic than poles
How do cryospheric processes affect the water cycle?
Cryospheric processes change amount of water stored in cryosphere - varies with temperature
How do periods of global cold affect water storage in the cryosphere?
Inputs>outputs
Input = snow
output = melting
How do periods of global warming affect water storage in the cryosphere?
Inputs < outputs
Inputs = snow
outputs = melting
How is water storage in the cryosphere affected over short timescales?
Annual temp fluctuations - more snow in winter than summer
