1.2.1 Introduction to the water cycle

Question 1

All water on the planet is described as part of the …

Answer 1

Hyrosphere

Question 2

What are the following four stores that make up the hydrosphere?

Answer 2

• Oceanic water
• Cryospheric water
• Terrestrial water
• Atmospheric water

Question 3

Oceanic water

Answer 3

• The largest store of water on earth.
• Accounts for 97% of the earth’s water in total.
• Oceans cover 72% of the Earth’s surface.
• Broken up into oceans and seas.
• Oceanic water is salty with a falling pH.

Question 4

Cryospheric water

Answer 4

• Water that is stored on earth in solid form (ice).
• Stores of cryospheric water includes sea ice, permafrost, ice sheets, ice caps and glaciers.

Question 5

Terrestrial water

Answer 5

Freshwater that is on the earth, including:
o Surface water – Water on the Earth’s surface, e.g. in rivers and lakes.
o Biological water – Water stored within biomass (in plants and animals).
o Groundwater
o Soil water

Question 6

Atmospheric water

Answer 6

• Can be held in all three states – solid , liquid or gas (water vapour).
• Water held in the atmospheric acts as a greenhouse gas and is used to control the Earth’s temperature.

Question 7

Accessibility of water

Answer 7

• Water must be physically and economically accessible.
• Only 0.01% of all the water of the planet is accessible to us.
• Accessible water is mainly only available from rivers, ice/permafrost, swamps, marshes, soil moisture, the atmosphere, and lakes.

Question 8

Change in the magnitude of water stores

Answer 8

Water can change between solid, liquid and gaseous forms. For water to boil or melt, it has to gain energy. For water to condense or freeze, it has to lose energy.

Question 9

Blue water

Answer 9

All parts of the water cycle that are visible.

Question 10

Green water

Answer 10

Any parts of the water cycle that are invisible (to the human eye).

Question 11

Fossil water

Answer 11

Water is so deep that is unusable for humans.

Question 12

Latent heat

Answer 12

The heat required to convert a solid into a liquid or vapour, or a liquid into a vapour without a change in temperature.

Question 13

Residence time

Answer 13

The average length of time each water molecules are stored in each store.

Question 14

Residence time for:
- Oceans
- Atmosphere
- Groundwater

Answer 14

• Oceans = 3,600 years
• Atmosphere = 10 days
• Groundwater = Up to 10,000 years.

Question 15

Soil water budget

Answer 15

The annual balance between precipitation, evapotranspiration and runoff.

Question 16

Water table

Answer 16

The upper level of saturated rock.

This rises and falls in response to groundwater flow, water abstraction by people or additional water flowing into the rock. The water table should be kept in equilibrium.

Question 17

What are acquifers?

Answer 17

Vast underground reservoirs deep below the ground surface which stores freshwater.

Question 18

What percentage of freshwater is stored in acquifers?

Answer 18

30%

Question 19

Where do acquifers commonly form?

Answer 19

Porous rocks (containing pores – air pockets) and permeable (allow water to pass through) such as chalk and sandstone.

Question 20

What are some of the impacts of extracting water from acquifers?

Answer 20

• Overabstraction
• Salt water intrusion

Question 21

What is salt water intrusion?

Answer 21

Where saline water from the oceans/seas contaminates freshwater in acquifers.

Question 22

Global hydrological cycle

Answer 22

The idea that water is continuously cycled between different stores.

Question 23

Is the global hydrological cycle a closed or open system?

Answer 23

Closed system as there are no inputs or outputs of water.

Question 24

Flows in the water cycle

Answer 24

• Evaporation
• Condensation
• Precipitation
• Cyrospheric processes (accumulation and ablation)

Question 25

Evaporation

Answer 25

Evaporation is when water is turned from a liquid to a gas.

This process increases the amount of water stored in the atmosphere.

Question 26

Factors affecting evaporation

Answer 26

• Energy (often from solar radiation)
• Availability of water
• Humidity
• Temperature

Question 27

Condensation

Answer 27

Condensation is when water is turned from a gas to a liquid.

Condensation decreases the amount of water stored in the atmosphere as water droplets transfer to other subsystems. E.g. When water vapour condenses it can form dew on leaves.

The magnitude of condensation depends on the amount of water in the atmosphere and temperature. E.g. When there is lots of water vapour and a large or rapid drop in temperature, condensation will be high.

Question 28

Precipitation (and cloud formation)

Answer 28

Precipitation is the main flow of water from the atmosphere to the ground.

Water vapour condense into water droplets when warm air cools down. This gathers as clouds. When the droplets get big enough, they fall as precipitation.

Question 28

How do clouds form?

Answer 28

Clouds form when warm air cools down, causing water vapour in it to condense into water droplets, which gather as clouds. When the droplets get big enough, they fall as precipitation.

Question 29

Factors that cause warm air to cool, leading to precipitation

Answer 29

• Topography: When warm air meets mountains, it is forced to rise, causing it to cool. This results in orographic precipitation.
• Convection: 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 convectional precipitation.
• Other air masses: Warm air is less dense than cool air. 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 30

Does cloud formation and precipitation stay constant throughout the year or does it vary?

Answer 30

Cloud formation and precipitation can vary seasonally (e.g. in the UK there’s normally more rainfall in winter than in summer) and by location (precipitation is usually higher in the tropics than at the poles).

Question 31

Accumulation

Answer 31

Input in the cryosphere.

Question 32

Ablation (melting)

Answer 32

Output in the cryosphere.

Question 33

What do cryospheric processes do to the water cycle?

Answer 33

Cryospheric processes such as accumulation and ablation change the amount of water stored as ice in the cryosphere.

Question 34

How do cryospheric processes vary?

Answer 34

• During periods of global cold, inputs into the cryosphere are greater than outputs – water is transferred to it as snow, and less water is transferred away due to melting.
• During periods of warmer global temperatures, the magnitude of the cryosphere store reduces as losses due to melting are larger than the inputs of snow.