The Drainage Basin Is An Open System Within The Global Hydrological Cycle

Question 1

What is the only input into the system?

Answer 1

Precipitation

Question 2

What is precipitation?

Answer 2

Any product of the condensation of atmospheric water vapour that falls under gravity

Question 3

What are the three main types of precipitation?

Answer 3

Orographic
Frontal
convectional

Question 4

What is orographic rainfall?

Answer 4

Rain that is produced from the lifting of moist air over a mountain

Question 5

What is frontal rainfall?

Answer 5

It occurs when a warm front meets a cold front
The heavier cold air sinks to the ground and the warm air rises above it
The rising warm air cools
The cooler air condenses to form clouds
The clouds bring heavy rain

Question 6

What is convectional rainfall?

Answer 6

When the suns energy (insolation) heats the earths surface and causes water to evaporate creating water vapour
The warm moist air then rises and cools and then condensates forming clouds
This leads to precipitation

Question 7

What do all types of precipitation have in common?

Answer 7

Air being forced to rise
As the air rises it cools and cannot hold as much moisture as when it was warmer

Question 8

What is a drainage basin?

Answer 8

An area of land drained by a river and its tributaries (river system)
Includes water in the water table and surface run-off

Question 9

Is a drainage basin an open of closed system?

Answer 9

An open system as it has inputs, storage, transfers and outputs

Question 10

What physical factors affect drainage basin input and flows and outputs ?

Answer 10

Slope gradient
Basin size (lag time)
Rock type ( permeable impermeable)
Rainfall type
Rainfall intensity
Basin shape
Drainage density
Vegetation type and cover

Question 11

How do humans disrupt the local hydrological cycle?

Answer 11

Urbanisation
Deforestation
Afforestation
Water extraction

Question 12

How does urbanisation affect the hydrological cycle?

Answer 12

Reduces infiltration and lag time
Impermeable surfaces
Increased discharge

Question 13

How does deforestation affect the local hydrological cycle?

Answer 13

Reduces interception, evapotranspiration
Increased infiltration/ saturation
Increased surface run-off
High soil erosion (no root binding)

Question 14

How does afforestation affect the local hydrological cycle?

Answer 14

Increasing interception and evapotranspiration
Reduce discharge in the drainage basin
Can take a long time for trees to mature

Question 15

How does water extraction affect the local hydrological cycle?

Answer 15

Reduces discharge in the basin

Question 16

How does basin size affect inputs/outputs and flows?

Answer 16

Influences lag time
Large drainage basin = increased lag time
Small basin = reduced lag time

Question 17

How does basin shape affect inputs/ outputs/ flows?

Answer 17

Circular drainage basin means all points are equidistant so short lag time higher peak discharge

Elongated basin longer lag time and lower peak discharge as water has to drain from the furthest point of watershed

Question 18

How does elevation and slope affect inputs/outputs/ flows?

Answer 18

Steeply sided valley means gravity assists water into channel = short lag time and high peak discharge

Gentle slopes have higher lag time and lower peak discharge

Question 19

How does rock type affect inputs/outputs/ flows?

Answer 19

Permeable rock assists percolation so long lag time

Impermeable rock doesn’t allow drainage so high surface run-off short lag time

Question 20

How does soil type affect inputs/outputs/flows?

Answer 20

Controls rate of infiltration, soil moisture, storage and rate of throughflow
Sandy soils have high infiltration rates so long lag time
Clay and silts have low infiltration so short lag time

Question 21

How does drainage density affect inputs/outputs/flows?

Answer 21

Total length of streams in a drainage basin divided by basin area
Basin with impermeable rock/soil have high drainage density due to lack of infiltration/ percolation
Basin with permeable rock/soil have low drainage density

Question 22

How does rainfall type affect inputs/outputs/flows?

Answer 22

Amount and duration determine ground saturation
Long periods of rain mean field capacity is met less infiltration more run-off = reduced lag time

Question 23

What is field capacity ?

Answer 23

Saturation capacity the amount of moisture in the soil before it becomes saturated

Question 24

How does rate of evapotranspiration affect inputs/outputs/flows?

Answer 24

Not constant all year round
High temp in summer increase rate reducing discharge
Low winter temps reduce evapotranspiration

Question 25

What is cloud seeding?

Answer 25

When silver iodine pellets or ammonium nitrate act as condensation nuclei to attract water droplets aim is to increase rainfall

Question 26

Where did the coverack flood happen?

Answer 26

Coverack Cornwall
South west England

Question 27

When did the coverack flood happen?

Answer 27

July 18th 2017

Question 28

What happened in coverack?

Answer 28

Flash flooding caused by intense rainfall over a short period

Question 29

How much rainfall happened in coverack?

Answer 29

200mm in 3 hours

Question 30

What caused the coverack flood?

Answer 30

Convectional rainfall
Temperatures were the 4th hottest summer since 1910
Temp in July was 33*c meaning convectional rainfall could occur

Question 31

What is the ITCZ?

Answer 31

Inter tropical convergence zone

Question 32

How does the ITCZ affect the hydrological cycle?

Answer 32

Seasonal shifts in the location of the ITCZ drastically affects rainfall in many equatorial nations, resulting in the wet and dry seasons of the tropics rather than the cold and warm seasons of higher latitudes. Longer term changes in the ITCZ can result in severe droughts or flooding in nearby areas