The Water Cycle

Question 1

Basic facts about water

Answer 1

Most of this is saline water in the oceans. Less than 3% is freshwater (which most species, including humans, need to survive).
69% is frozen in the cryosphere.
30% is groundwater (water stored underground in the lithosphere).
0.3% is liquid freshwater on the Earth’s surface in lakes, rivers etc.
0.04% is stored as water vapour in the atmosphere.

Question 2

Water is stored in solid, liquid and gas forms

Answer 2

Water can change between solid, liquid and gaseous forms. For water to boil or melt, it has to gain energy (e.g. from the Sun). For water to condense or freeze, it has to lose energy.

Question 3

Water is constantly cycling between stores

Answer 3

Water is continuously cycled between different stores. This is known as the global hydrological cycle.
The global hydrological cycle is a closed system - there are no inputs or outputs of water.

Question 4

Evaporation

Answer 4

Evaporation occurs when liquid water changes state into a gas, becoming water vapour-it gains energy, normally from solar radiation. Evaporation increases the amount of water stored in the atmosphere.

Question 5

Condensation

Answer 5

Condensation occurs when water vapour changes state to become a liquid- -it loses energy to the surroundings. It happens when air containing water vapour cools to its dew point (the temperature at which it will change from a gas to a liquid)

Question 6

Cloud Formation

Answer 6

Cloud formation and precipitation are essential parts of the water cycle -precipitation is the main flow of water from the atmosphere to the ground.
Clouds form when warm air cools down, causing the water vapour in it to condense into water droplets, which gather as clouds. When the droplets get big enough, they fall as precipitation.

Question 7

Other air masses

Answer 7

Warm air is less dense than cool air. As a result, when warm air meets cool air, the warm air is forced up above the cool air. It cools down as it rises.
This results in frontal precipitation

Question 8

Topography

Answer 8

When warm air meets mountains, it’s forced to rise, causing it to cool. This results in orographic precipitation.

Question 9

Convection

Answer 9

when the sun heats up the ground, moisture on the ground evaporates and rises up in a column of warm air. As it gets higher, it cools. This results in convective precipitation.

Question 10

Cryospheric Processes

Answer 10

Cryospheric processes such as accumulation and ablation change the amount of water stored as ice in the cryosphere. The balance of accumulation and ablation varies with temperature

Question 11

Ablation

Answer 11

output of water from a glacier