Drainage Basins

Question 1

what is a drainage basin

Answer 1

an area of land drained by a river and its tributaries and can be referred to as a river catchment area.

at a local scale, hydrological processes operate within these areas and it is an open system which has inputs and outputs which causes the amount of water to vary.

Question 2

what are the physical factors which influence a drainage basin

Answer 2

Climate
Soils
Geology
Relief
Vegetation

Question 3

how does climate effect a drainage basin

Answer 3

role in influencing the amount of precipitation overall and the amount of evaporation. This also has an impact on vegetation

Question 4

how do soils effect a drainage basin

Answer 4

determines the amount infiltration, through flow and indirectly, the type of vegetation

Question 5

how does geology effect a drainage basin

Answer 5

This can impact subsurface processes such percolation and ground waterflow (and therefore aquifers) It can indirectly alter soil formation

Question 6

how does relief effect a drainage basin

Answer 6

Altitude can impact on precipitation totals. Slopes can effect the amount of runoff

Question 7

how does vegetation effect a drainage basin

Answer 7

Presence/absence has impact on rate of interception, infiltration and occurrence of overland flows as well as transpiration

Question 8

what are the 3 main human factors effecting drainage basins

Answer 8

• over abstraction
• land use change
• deforestation

Question 9

how does over abstraction affect drainage basins

Answer 9

• impact on precipitation

- impacts evaporation and evapotranspiration

Question 10

how does land use change affect drainage basins

Answer 10

-impacts on evapotranspiration/ evaporation

Question 11

how does deforestation affect drainage basins

Answer 11

• impacts interception

- impacts evaporation and evapotranspiration

Question 12

how much of the global rainforests does the amazon rainforest make up?

Answer 12

60%

Question 13

how much of the amazon basin vegetation has been deforested in last 50 years

Answer 13

20%

which hugely affects water cycles and carbon cycles

Question 14

what proportion of worlds species live in amazon

Answer 14

half

Question 15

what caused deforestation in 1970s in amazon

Answer 15

military to find resources

Question 16

what factors have led to destruction of amazon

Answer 16

• cattle grazing
• trans amazonian railway
• soy beans/ farming
• resources

Question 17

how much of amazon is cut down yearly

Answer 17

20,000 km2 a year

Question 18

compare how much of the rainforest was protected before and after 2012

Answer 18

before 28%

now 47%

more strict reserves, sustainable use, indigenous people allowed to preserve forest

Question 19

what % increase in deforestation would be catastrophic for the environment

Answer 19

20-25%

Question 20

expalin how physical features of a drainage basin can affect the shape of storm hydrographs

Answer 20

> Human induced factors such as how dense the vegetation is in the basin and impermeable surfaces like concrete caused by urbanisation decrease lag time

> natural physical features such as how steep the topography is and how big the basin is
eg)murray darling basin is large

Question 21

what is a river regime

Answer 21

the annual variations in discharge of a river and is measured at particluar points or gauging stations along a river

Question 22

why might river regimes vary between basins

EXAM QUESTION

Answer 22

-human activities: like dam building or effecting the amount of vegetation cover in the area
>dam building can regulate flow and decrease discharge downstream
>vegetation such as wetlands can hold more water and release it slowly into the system

-natural factors like geology or soil type and the size of basin
geology- permeability of rocks effects amount of water stored in groundwater stores which is gradually released into the river and regulates its flow
more permeable rocks like sandstone or fractured igneous rocks