3.1.1.2 The water cycle

Question 1

Description of the lithosphere

Answer 1

• surface water, including biological and groundwater
• Finland and Canada have the most lakes

Question 2

Description of the hydrosphere

Answer 2

• oceans cover 70% of the earth’s surface
• contains 97% of water
• saline

Question 3

Description of the cryosphere

Answer 3

• water held in ice
• if ice sheets melted, sea levels would rise by 60m

Question 4

Description of atmosphere

Answer 4

• commonly water vapour
• warm air holds more vapour than cold air
• increase in water vapour leads to an increase in temperatures (positive feedback)
• absorbs and reflects solar radiation

Question 5

Name the 5 factors driving the change in water stores

Answer 5

• evaporation
• condensation
• cloud formation
• precipitation
• cryospheric processes

Question 6

What do the rates of evaporation depend upon

Answer 6

• amount of solar energy
• the availability of water
• humidity of the air (the more humid the air, the less evaporation)
• temperature of the air (warmer air can hold more water)

Question 7

Define relative humidity

Answer 7

The amount of water vapour in the air compared to how much it could possibly hold at that temperature.

Question 8

How could condensation occur

Answer 8

• air is cooled
• there is a fall in pressure

Question 9

What does cloud formation require

Answer 9

A condensation nuclei

Question 10

Define dew point

Answer 10

The point where the air is at maximum saturation

Question 11

What are the two main causes of precipitation

Answer 11

• air temperature is reduced to dew point
• volume of air increases as it rises, without an increase in temperature (adiabatic cooling)

Question 12

Define orographic rainfall

Answer 12

Air is forced to rise over hills/ mountains

Question 13

Define convectional rainfall

Answer 13

Warm air rises away from surfaces and cools

Question 14

Define frontal rainfall

Answer 14

Air masses of different temperatures meet and the warm air rises

Question 15

Define accumulation

Answer 15

Inputs of a glacial system due to snowfall compressing into glacial ice

Question 16

Define ablation

Answer 16

Outputs of a glacial system due to melting

Question 17

Define sublimation

Answer 17

Ice changing directly into water vapour

Question 18

What is a drainage basin

Answer 18

An area of land drained by a river and its tributaries

Question 19

What is the name of the boundary of a drainage basin

Answer 19

Watershed

Question 20

Define evapotranspiration

Answer 20

Combined loss of water through evaporation and transpiration

Question 21

Define runoff

Answer 21

The output of water from the drainage basin system as it moves across the surface

Question 22

Define interception as a store

Answer 22

A short term storm where vegetation can hold precipitation on leaves and branches

Question 23

Define surface storage

Answer 23

Puddles
Generally more common in built environments where there is less infiltration

Question 24

Define soil water storage

Answer 24

Pore spaces between soil particles fill with water

Question 25

What percentage of sand is pore spaces

Answer 25

20-45%

Question 26

What percentage of clay is pore spaces

Answer 26

40-60%

Question 27

Define groundwater storage

Answer 27

Water stores underground in permeable and porous rocks

Question 28

Define channel store

Answer 28

The volume of water in a river channel

Question 29

Define stemflow

Answer 29

Water flowing down the stems of plants and trees

Question 30

Define infiltration

Answer 30

Water which soaks into the soils

Question 31

Define overland flow

Answer 31

Rainfall which flows over the ground because the soil is saturated or because rainfall exceeds infiltration capacity

Question 32

Define channel flow

Answer 32

The flow of water in rivers

Question 33

Define throughfall

Answer 33

Water moving from vegetation to the ground

Question 34

Define throughflow

Answer 34

The lateral movement of water down a slope to a river channel

Question 35

Define percolation

Answer 35

Downward movement of water to underground stores

Question 36

Define groundwater flow

Answer 36

Slow movement of water within saturated rock

Question 37

Factors affecting infiltration rate

Answer 37

- increased vegetation means an increased rate (roots) - the gradient of hill slopes (topography) - the flow supply

Question 38

Main factor affecting soil storage

Answer 38

Type of soil (sand or clay)

Question 39

Factors affecting interception rates

Answer 39

- type of vegetation (coniferous intercepts 35% precipitation whereas deciduous intercepts 25% annually) - plant density - precipitation intensity

Question 40

Define the water balance

Answer 40

The long term balance between the inputs and outputs of a drainage basin system

Question 41

Define positive water balance

Answer 41

Precipitation exceeds evapotranspiration

Question 42

How do seasonal changes affect the water balance

Answer 42

- In winter, the increased precipitation may lead to a soil moisture surplus and increased runoff - In summer, utilisation of water by humans and vegetation may be high and there could be a soil moisture defecit

Question 43

What measures river flow

Answer 43

Discharge

Question 44

How do drainage basin characteristics affect the flood hydrograph

Answer 44

Larger drainage basins catch more precipitation meaning a large peak discharge, however this discharge must travel further so there is a lower lag time. Opposite for small drainage basins

Question 45

How does the amount of water already present in the drainage basin (antecedent moisture) affect lag time.

Answer 45

If the soil is already saturated, there will be more surface runoff (the fastest flow) therefore there will be a shorter lag time.

Question 46

How does rock type affect the flood hydrograph

Answer 46

Impermeable rock reduces infiltration, increases surface runoff, reducing lag time. Peak discharge increases as more water reaches the river faster

Question 47

Human factors on the storm hydrograph

Answer 47

- Impermeable surfaces increases runoff - Man made drainage systems also reduce lag time

Question 48

How do storm events change the water cycle over time

Answer 48

During a storm event there is less infiltration, more surface runoff and therefore more flooding

Question 49

How do seasonal events change the water cycle over time

Answer 49

- wet seasons have a water surplus - dry seasons have a water deficit (link to water balance)

Question 50

How do farming practices change the water cycle over time

Answer 50

- huge quantities of water are used in food production which redistributes water away from natural pathways - farmers dig ditches to avoid waterlogging plants which increases overland flow - depleted groundwater stores to be used for irrigation

Question 51

How does water abstraction change the water cycle over time

Answer 51

- the process of taking water from a ground source - can cause rivers to dry up and damage to wetland environments - salt water intrusion in coastal areas

Question 52

How does Israel combat against abstraction

Answer 52

- 86% water reuse - 600,000m^3 per day desalination plant

Question 53

How does deforestation change the water cycle over time

Answer 53

- lowers evapotranspiration and interception - increases overland flow and throughflow as vegetation usually slows down these processes - increased discharge and increased risk of flooding