Drainage basins

Question 1

What is a drainage basin?

Answer 1

An open, local hydrological system where rain falling on land flows into a river.

A drainage basin is also referred to as a river’s catchment.

Question 2

What is the boundary of a drainage basin called?

Answer 2

Watershed.

Precipitation falling beyond the watershed enters a different drainage basin.

Question 3

What are the main inputs and outputs of a drainage basin?

Answer 3

Inputs: Precipitation
Outputs: Evaporation, transpiration, and channel flow

The total amount of water in the system changes over time.

Question 4

How do the size and shape of a drainage basin affect its processes?

Answer 4

Larger basins with steep sides catch precipitation quickly and have high drainage density

Smaller basins or those with fewer streams have low drainage density.

Question 5

What causes more precipitation to occur?

Answer 5

The cooling of air increases the rate of condensation.

This leads to various types of precipitation.

Question 6

What is frontal rainfall?

Answer 6

Occurs when warm air is forced up above cool air, causing it to cool and precipitate

Warm air is less dense than cool air.

Question 7

What is relief rainfall?

Answer 7

Occurs when warm air meets mountains and is forced to rise, causing it to cool

This type of precipitation is associated with mountainous regions.

Question 8

What is convectional rainfall?

Answer 8

Occurs when the sun heats the ground, causing moisture to evaporate and rise, then cools down

This results in precipitation as the air rises.

Question 9

Why do coastal areas often receive more precipitation than inland areas?

Answer 9

Because water evaporated from oceans falls as precipitation

This results in higher moisture availability near coastlines.

Question 10

What is interception in the context of drainage basins?

Answer 10

Water landing on vegetation or structures before reaching the soil.

Question 11

Define infiltration.

Answer 11

Water soaking into the soil.

Question 12

What is direct runoff?

Answer 12

Water flowing over the land when rain falls faster than infiltration can occur.

Question 13

What is saturated overland flow?

Answer 13

Water flowing over the land because the soil can no longer absorb more water.

Question 14

Explain throughflow.

Answer 14

Water moving slowly downhill through the soil.

Question 15

What does percolation refer to?

Answer 15

The transfer of water from the surface into the bedrock beneath.

Question 16

What is groundwater flow?

Answer 16

Water slowly flowing through permeable rock below the water table.

Question 17

What is evaporation?

Answer 17

Water turning into water vapour.

Question 18

Define transpiration.

Answer 18

Evaporation from within leaves of plants.

Question 19

What is evapotranspiration?

Answer 19

The process of evaporation and transpiration together.

Question 20

What is channel flow/river discharge?

Answer 20

Water leaving the drainage basin through a river or stream.

Question 21

What seasonal impact does winter have on drainage basins?

Answer 21

Temperatures may drop below 0 °C, causing water to freeze and reducing flows.

Question 22

How does an increase in temperature affect drainage basins?

Answer 22

It can lead to larger flows as ice melts and more evaporation occurs.

Question 23

What is the relationship between intense storms and drainage basins?

Answer 23

They generate more precipitation and greater peak discharges than light rain showers.

Question 24

Fill in the blank: Infiltration rates are influenced by _______.

Answer 24

soil type, soil structure, and existing soil moisture.

Question 25

How does soil type affect throughflow?

Answer 25

Throughflow is faster through openings like cracks or animal burrows.

Question 26

What role does vegetation play in drainage basins?

Answer 26

It intercepts precipitation and slows its movement into the river channel.

Question 27

How does geology affect groundwater flow?

Answer 27

Permeable rocks allow faster groundwater flow, while impermeable rocks increase direct runoff.

Question 28

What is the effect of relief on drainage processes?

Answer 28

Steeper gradients lead to faster runoff and shorter residence times for surface stores.

Question 29

List the physical factors within drainage basins that influence inputs, flows and outputs.

Answer 29

* Seasons and climate * Soil * Vegetation * Geology * Relief

Question 30

True or False: Increased vegetation leads to higher runoff and peak discharge.

Answer 30

False

Question 31

What happens to the water table during percolation?

Answer 31

Water seeps down into the water table.

Question 32

How does deforestation affect processes in the drainage basin?

Answer 32

It reduces the amount of water intercepted by vegetation, increasing direct runoff. It reduces the rate of evapotranspiration, leading to less water vapour in the atmosphere. ## Footnote Deforestation leads to less dead plant material on the forest floor, which normally helps retain water.

Question 33

What is the impact of soil erosion on rainwater storage?

Answer 33

It reduces the soil's ability to store rainwater ## Footnote Exposed land is more prone to erosion, leading to decreased infiltration.

Question 34

How does ploughing affect water runoff?

Answer 34

It breaks up the surface, allowing more water to infiltrate and reducing runoff ## Footnote This agricultural practice can enhance soil permeability.

Question 35

What effect does livestock farming have on soil infiltration?

Answer 35

It compacts and tramples the soil, decreasing infiltration and increasing runoff ## Footnote Cattle and other livestock can severely impact soil structure.

Question 36

What is the consequence of buildings and roads on land?

Answer 36

They create an impermeable layer, preventing infiltration and increasing runoff ## Footnote Urban development significantly alters natural drainage patterns.

Question 37

How do urban drainage systems affect river discharge?

Answer 37

They feed rivers with rainwater more quickly, increasing discharge ## Footnote This can lead to heightened flood risks in urban areas.

Question 38

What is the purpose of creating new storage reservoirs?

Answer 38

To increase the amount of freshwater accessible to humans ## Footnote Dams can also reduce river discharge into oceans.

Question 39

What happens to evaporation levels when large areas of standing water are created?

Answer 39

Evaporation levels increase ## Footnote This can affect local climates and water availability.

Question 40

During dry seasons, what happens to water abstraction?

Answer 40

More water is abstracted, especially groundwater and from reservoirs ## Footnote This leads to further depletion of water stores.

Question 41

What is Amazonia known for?

Answer 41

It is the world's largest tropical rainforest, covering 40% of South America's landmass. ## Footnote Its vast size contributes to significant global biodiversity.

Question 42

How does the water cycle affect rainfall in the Amazon?

Answer 42

Evaporation over the Atlantic Ocean contributes to very high rainfall ## Footnote This moisture is transported to the Amazon by prevailing winds.

Question 43

What is the effect of high temperatures on the rainforest's water cycle?

Answer 43

They increase the evapotranspiration rate ## Footnote This enhances local convectional precipitation.

Question 44

What happens to water flow in deforested areas of the Amazon?

Answer 44

Increased water reaches the ground, leading to saturated overland flow ## Footnote This raises the risk of flooding due to lack of interception.