Drainage Basin

Question 1

What is a drainage basin?

Answer 1

It is a sub-system within the hyrdological system. It is an area drained by a river and its tributaries.

Question 2

Is a drainage basin a closed or open system?

Answer 2

It is an open system as it has external inputs and outputs. The variations of water in the system can happen at different scales - daily, seasonally or annually.

Question 3

How do drainage basins lose water?

Answer 3

• Evaporation and Evapotranspiration into the atmosphere.
• Surface run-off to the sea
• Percolation into groundwater stores

Question 4

What causes movement within a drainage basin?

Answer 4

Solar energy and gravity.

Physical and human factors too.

Question 5

What are the 5 physical factors that impact a drainage basin?

Answer 5

Climate
Souls
Geology
Relief
Vegetation

Question 6

How does the climate impact the drainage basin?

Answer 6

• main influence on inputs

- affects rate of evaporation

Question 7

How does the soils impact the drainage basin?

Answer 7

• soils directly effect the rate of infiltration

- indirectly impacts the type of vegetation that can grow

Question 8

How does the geology impact the drainage basin?

Answer 8

• impacts the subsurface processes

- geology alters soil formation

Question 9

How does the relief impact the drainage basin?

Answer 9

• slopes increase surface run off

- slopes decrease infiltration rates

Question 10

How does the vegetation impact the drainage basin?

Answer 10

• more vegetation means more water is intercepted
• more veg can reduce infiltration
• less veg can lead to more overland flow
• the rate of transpiration is increased

Question 11

Name 5 human factors that influence the drainage basin.

Answer 11

• deforestation
• afforestation
• land use
• Dam Building
• manufacturing

Question 12

How does deforestation impact the drainage basin?

Answer 12

• more infiltration as there is less interception of trees

- depends on area as high climate and deforestation could lead to desertification

Question 13

How does afforestation impact the drainage basin?

Answer 13

• less infiltration as there is more trees to intercept the precipitation
• with young trees, there is immediate increase in run off and more sediment loss as it is washed away.
  30 years later there is less surface run off

Question 14

How does dam building impact the drainage basin?

Answer 14

• increased evaporation rates as an increase in enormous artificial reservoirs behind dams

Question 15

How does land use impact the drainage basin?

Answer 15

• if the land is impermeable there is more surface run off

- infiltration is greater under forests compared to grassland

Question 16

How does manufacturing impact the drainage basin?

Answer 16

• water used by manufacturing has increased the amount of groundwater extracted - ground water levels rise and surface flooding occurs