Topic 5: The Water Cycle and Water Insecurity

Question 1

closed system

Answer 1

inputs = outputs, there are no inputs or outputs of matter from an external source

Question 2

solar energy

Answer 2

energy from the sun, heating water and causing evaporation/transpiration

Question 3

gravitational potential energy

Answer 3

ways in which water accelerates under gravity, thus transporting it to rivers and eventually to the sea

Question 4

precipitation

input

Answer 4

moisture in any form, e.g. rain, snow, sleet and hail

Question 5

interception

storage

Answer 5

temporary storage, as water is captured by plants, buildings and hard surfaces before reaching the soil

Question 6

vegetation storage

storage

Answer 6

any moisture taken up by vegetation and held within plants

Question 7

surface storage

storage

Answer 7

any surface water in lakes, ponds and puddles

Question 8

soil moisture

storage

Answer 8

water held within the soil

Question 9

groundwater storage

storage

Answer 9

water held within permeable rocks (also known as an aquifer)

Question 10

channel storage

storage

Answer 10

water held in rivers and streams

Question 11

infiltration

flow

Answer 11

water entering the topsoil, most common during slow or steady rainfall

Question 12

throughflow

flow

Answer 12

water seeping laterally through soil below the surface, but above the water table

Question 13

percolation

flow

Answer 13

the downward seepage of water through rock under gravity, especially in permeable rocks e.g. sandstone and chalk

Question 14

stem flow

flow

Answer 14

water flowing down plant stems or drainpipes

Question 15

groundwater flow

flow

Answer 15

slow-moving water that seeps into a river channel through rocks

Question 16

channel flow

flow

Answer 16

the volume of water flowing within a river channel

Question 17

surface runoff

flow

Answer 17

flow over the surface during an intense storm, or when the ground is frozen, saturated or impermeable

Question 18

evaporation

output

Answer 18

the conversion of water to vapour

Question 19

transpiration

output

Answer 19

water taken up by plants and transpired from the leaf surface

Question 20

evapotranspiration

output

Answer 20

the combined effect of evaporation and transpiration

Question 21

river discharge

output

Answer 21

the volume of water passing a certain point in the channel over a certain amount of time

Question 22

potential evapotranspiration (PE)

Answer 22

an estimate of the amount of water lost through evaporation and transpiration in any given period, depending on temperature and air humidity

Question 23

positive feedback

Answer 23

when a change leads to a decrease within a system and creates instability

Question 24

negative feedback

Answer 24

when a change tends to reinforce a system, leading to stability

Question 25

tipping point

Answer 25

when a system changes from one state to another, irretrievably

Question 26

resilience

Answer 26

the ability of a system to ‘bounce back’ and survive

Question 27

Walker Cell

Answer 27

the circulation of air whereby upper atmospheric air moves eastwards, and surface air moves west across the Pacific, causing trade winds

Question 28

water scarcity

Answer 28

an imbalance between demand and supply of water

Question 29

physical scarcity

Answer 29

insufficient water to meet demand

Question 30

economic scarcity

Answer 30

people cannot afford water, even when it’s available

Question 31

water stress

Answer 31

if a country’s water consumption exceeds 10% of its renewable freshwater supply, including difficulties in obtaining new quantities of water, as well as poor water quality restricting usage

Question 32

water insecurity

Answer 32

the state where present and future supplies of water cannot be guaranteed, caused by water scarcity and water stress

Question 33

virtual water

Answer 33

water transferred by trading in crops and services that require large amounts of water for their production

Question 34

aquifer

Answer 34

an underground reservoir most commonly formed in rocks such as chalk and sandstone

Question 35

convectional rainfall

Answer 35

when the ground warms up, evaporation takes place and the air above is heated and rises - the rainfall created is often intense and associated with electrical storms and thunder

Question 36

cryosphere

Answer 36

the frozen part of the Earth’s hydrological system

Question 37

flux

Answer 37

refers to the movement or transfer of water between stores

Question 38

frontal rainfall

Answer 38

formed when warmer moist air meets colder Polar air - the warmer air is forced to rise over the denser colder air, creating low-pressure and rain

Question 39

Inter-Tropical Convergence Zone (ITCZ)

Answer 39

a narrow zone of low pressure near the Equator where northern and southern air masses converge

Question 40

orographic rainfall

Answer 40

when warm, moist air is forced to rise over upland areas, causing the moisture to condense and create rainfall

Question 41

rain-shadow effect

Answer 41

when orographic rainfall has occurred over an upland area, the area on the lee side of the hills will receive less rain because the air descends, warms and becomes drier

Question 42

store

Answer 42

an accumulation or quantity of water in a system

Question 43

thermohaline circulation

Answer 43

the flow of warm and cold water that circulates around the world’s oceans

Question 44

water budget

Answer 44

the difference between inputs of water (e.g. precipitation) and outputs of water (e.g. evapotranspiration) in any given area