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Flashcards in EQ1 Deck (34)
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1
Q

where does the power that drives the global hydrological cycle come from

A

solar energy - in the form of heat

gravitational energy - causes rivers to flow downhill and precipitation to fall to the ground

2
Q

stores

A
reservoirs where waters held 
there are 4 main stores 
- oceans
- glaciers and ice sheets (the cryosphere)
- surface run-off
- the atmosphere
3
Q

flows

A
transfers of water from one to another 
there are 4 main flows: 
- precipitation
- evaporation
- transpiration
- vapour transport
4
Q

fluxes

A

the rates of flow between stores

the greatest fluxes occur over the oceans

5
Q

the global water budget

A

takes into account all the water held in the stores and flows of the global hydrological cycle
only 2.5% of it is freshwater; the rest is in the oceans

6
Q

the drainage basin

A

is a subsystem within the global hydrological cycle
its an open system with inputs and outputs
main input is precipitation

7
Q

interception (flow)

A

the retention of water by plants and soils which is subsequently evaporated or absorbed by the vegetation

8
Q

infiltration (flow)

A

the process by which water soaks into, or is absorbed by the soil

9
Q

percolation (flow)

A

similar to infiltration, but a deeper transfer of water into permeable rocks

10
Q

throughflow (flow)

A

the lateral transfer of water downslope through the soil

11
Q

groundwater (flow)

A

the very slow transfer of percolated water through pervious or porous rocks
also known as base flow

12
Q

surface run-off (flow)

A

the movement of water that is unconfined by a channel across the surface of the ground
also known as overland flow

13
Q

river or channel flow (flow)

A

takes over as soon as the water enters a river or stream; the flow is confined within a channel

14
Q

evaporation (output)

A

the process by which moisture is lost directly into the atmosphere from water surfaces , soil and rock

15
Q

transpiration (output)

A

the biological process by which water is lost from plants through minute pores and transferred to the atmosphere

16
Q

discharge/ channel flow (output)

A

into another, larger drainage basin, a lake or the sea

17
Q

physical factors affecting the drainage basin

A
climate
soils
geology
relief
vegetation
18
Q

how does climate affect drainage basin systems

A

climate has a role in influencing the type and amount of precipitation overall and the amount of evaporation, i.e. the major inputs and outputs
climate also has an impact on the vegetation type

19
Q

how do soils affect drainage basin systems

A

soils determine the amount of infiltration and throughflow and , indirectly geology affects soil formation

20
Q

how does geology affect drainage basin systems

A

geology can impact on subsurface processes such as percolation and groundwater flow [and therefore, on aquifers]
indirectly, geology affects soil formation

21
Q

how does relief affect drainage basin systems

A

relief can impact on the amount of precipitation

slopes can affect the amount of runoff

22
Q

how does vegetation affect drainage basin systems

A

the presence or absence of vegetation has a major impact on the amount of interception, infiltration and occurrence of overland flow, as well as on transpiration rates

23
Q

impacts of human activity on drainage basin systems

A

river management
deforestation
changing land use - agriculture
changing land use - urbanisation

24
Q

river management

A

construction of storage reservoirs holds back river flows
abstraction of water for domestic and industrial use reduces river flows
abstraction of groundwater for irrigation lowers water tables

25
Q

deforestation

A

clearance of trees reduces evapotranspiration, but increases infiltration and surface runoff

26
Q

changing land use - agriculture

A

arable to pastoral: compaction of soil by livestock increases overland flow
pastoral to arable: ploughing increases infiltration by loosening and aerating the soil

27
Q

changing land use - urbanisation

A

urban surfaces [tarmac, tiles, concrete] speed surface runoff by reducing percolation and infiltration
drains deliver rainfall more quickly to streams and rivers, increasing chances of flooding

28
Q

components of drainage basin most affected by humans

A
  • evaporation and evapotranspiration
  • interception
  • infiltration
  • groundwater
  • surface run-off
29
Q

Amazonia case study

A

contains the worlds largest area of tropical rainforest
deforestation here has disrupted the drainage basin cycle in a number of ways including:
- a lowering of humidities
- less precipitation
- more surface runoff and infiltration
- more evaporation, less transpiration
- more soil erosion and silt being fed into rivers

30
Q

what is a river regime

A

the annual variation in the discharge or flow of a river at a particular point and is usually measured in cumecs

31
Q

what influences a rivers regime

A
  • the size of the river and where discharge measurements are taken along its course
  • the amount, seasonality and intensity of the precipitation
  • the temperatures, with possible meltwater and high rates of evaporation in summer
  • the geology and soils, particularly their permeability and porosity; groundwater noted in permeable rocks is gradually released into the river as base flow
  • the type of vegetation cover: wetlands can hold water and release it slowly into the river
  • human activities aimed at regulating a rivers discharge
32
Q

water budget

A

the annual balance between precipitation, evapotranspiration and runoff
calculated with
P = E + R +/- S

33
Q

storm hydrographs

A

show discharge changes over a short period of time usually a few days
they put two things:
- the occurrence of a short period of rain over a drainage basin
- the subsequence discharge of the river

34
Q

main features of a storm hydrograph

A
  • once the rainfall starts, the discharge begins to rise; this is known as the rising limb
  • peak discharge is reached over some time after the peak rainfall because the water takes time to move over and through the ground to each the river
  • the time interval between peak rainfall and peak discharge is known as lag time
  • once the input of rainwater into the river starts to decrease, so does the discharge; this is shown by the falling or recessional limb
  • eventually the rivers discharge returns to its normal level or base flow