Water Cycle πŸ’§ Flashcards

1
Q

what is the systems approach?

A

group of interacting parts connected by flows of energy or matter

open - energy and matter can enter and leave
closed - only energy can enter and leave, matter cant

cascading systems - where output of one subsystem is an input to another

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2
Q

dynamic equilibrium in water cycle

A

tendency towards a natural state of balance between inputs and outputs
- change triggers + or - feedback

closed system - no water enters or leaves, recycled
drainage basin = open system, inputs and outputs can change

equilibrium upset by natural (storm events) and human changes

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3
Q

Positive feedback in the water cycle

A
  • temperature rise
  • evaporation increases
  • amount of water vapour in atmosphere increases
  • greenhouse effect increases
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4
Q

Negative feedback in water cycle

A
  • temperatures rise
  • evaporation increases
  • increase water vapour, causes more clouds to form
  • increased cloud coverage, reflect more sunlight back to space
  • temperatures fall
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5
Q

how are systems affected by feedbacks?

A

if input and outputs are balanced = dynamic equilibrium

  • positive - moves system further from equilibrium
  • negative - moves system closer to equilibrium
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6
Q

What is an open system?

A

Both energy and matter can enter and leave
- drainage basin, water (energy from sun and water)
- rainforest, carbon

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7
Q

What is a closed system?

A

Matter can’t enter or leave but energy can
- carbon cycle (energy from sun enters and leaves, but carbon remains same)

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8
Q

Flows in the water cycle

A

Evaporation - liquid to gas, uses solar energy, can be affected by seasons or glacial periods

Condensation - gas to liquid, water vapour cools to dew point, loses energy

Cloud formation - warm air cools and condenses onto condensation nuclei, varies seasonally and location

Precipitation - main flow from atmosphere to ground

Cryospheric processes - accumulation and ablation

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9
Q

Natural changes that impact the water cycle

A

Seasonal changes
Storm events

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10
Q

Human changes that impact water cycle

A

Deforestation
Urbanisation
Farming
water abstraction
climate change

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11
Q

what are β€˜processes driving change’?

A

factors affecting the size of stores in the water cycle
dictated by:
- flows (eg evaporation)
- global factors
- local factors

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12
Q

local processes driving change

A

flows and transfers
(in a drainage basin)

affecting by physical and natural factors

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13
Q

global processes driving change

A

cryospheric processes
clouds and precipitation
evaporation
condensation
climate change

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14
Q

effects of evaporation on the water cycle

A

increases the amount of water stored in atmosphere
from hydrosphere, biosphere etc

magnitude (rate) varies due to location and season:
- amount of solar energy
- availability of water (pond vs field)
- humidity (higher = less)
- temperature (warmer air holds more water)

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15
Q

effects of condensation on the water cycle

A

happens when air containing water vapour cools to dew point
(cool air holds less water)

decreases amount of water stored in atmosphere

condense on surfaces or particles below dew point temperature

magnitude depends on
- amount of water vapour in atmosphere
- temperature (large drop = more condensation)
- condensation nuclei

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16
Q

effects of cloud formation and precipitation on the water cycle

A

precipitation returns atmospheric water to terrestrial
- causes, water vapour cooled (see next)

magnitude depends on
- seasons (eg UK, more rain in winter than summer)
- location (higher at tropics than poles)

distribution affected by global atmospheric circulation model
- hot at equator = evaporation, low pressure
low pressure = clouds

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17
Q

causes of rainfall (3)

A

frontal - warm air is less dense, so when meets cool air, forced above
cools as it rises and condenses

orographic - warm air meets mountains, forced to rise
causes it to cool and condense

convectional - sun heats up ground, moisture evaporates and rises
cools as it gets higher, condenses

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18
Q

effects of cryospheric processes on the water cycle

A

changes to the amount of water stored in cryosphere
Major store of water

magnitude depends on
- season (more ice in winter)
- temperature

glacial periods - inputs in cryosphere greater than outputs, no melting
interglacial - outputs larger than inputs, melting
- causing sea level rise, more volume in hydrosphere

varies on different scales, annual or thousands of years (glacial periods)

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19
Q

effects of climate change on water cycle (global factors)

A

last ice age = increased size of store in cyrosphere
less storage in the hydrosphere

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20
Q

outline drainage basins

A
  • area of land drained by a river and its tributaries
  • boundary is called the watershed
  • open systems with inputs and outputs
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21
Q

inputs in a drainage basin

A

precipitation
- rain, snow etc

22
Q

stores in a drainage basin

A

interception storage
(especially in woodland)
temporary, evaporates or throughfall

vegetation storage - water taken up by plants

surface storage - puddles, ponds and lakes

soil storage - moisture in soil

groundwater storage - water stored in ground, soil or rocks (aquifers)

channel storage - water in river channel

23
Q

what is the water table?

A

top surface of the zone of saturation (area of soil or rock where all pores are full of water)

level where water has saturated the ground

24
Q

flows in a drainage basin

A

infiltration - water soaking into soil
influenced by: saturation, soil type

surface runoff - happens as water falls faster than infiltrated

throughfall - water dripping through leaves

stemflow - in stem or tree trunk

percolation - water moving downwards through bedrock and soil below water table

throughflow - lateral flow through soils above the water table
interflow - through rocks above water table

groundwater flow - water flowing below water table through permeable rock, very slow

base flow - groundwater flow that feeds into rivers

channel flow - water flowing in river

25
Q

outputs in a drainage basin

A

evaporation - water vapour in atmosphere

transpiration - evaporates from leaves into atmosphere

evapotranspiration

river discharge - into ocean

26
Q

what is the water balance?

A

balance between inputs (precipitation) and outputs (discharge and evapotranspiration)

water surplus - inputs exceed outputs
saturation, more runoff, river levels ruse

water deficit - outputs higher than inputs
groundwater stores depleted, used but not replaced
recharged in wet seasons

27
Q

outline a hydrograph (flood/storm)

A

shows river discharge over a period of time, a storm event

peak discharge - river discharge at its highest

lag time - delay between peak rainfall and peak discharge
takes time for water to flow into river
short lag time increased peak discharge

rising limb - river discharge is increasing

falling limb - river discharge is deceasing, less water flowing into river

throughflow - water passing throigh gaps in soil into river

groundwater (base) flow - main supply in normal conditions, from groundwater

28
Q

Purpose of hydrograph

A

Predict flooding
after storm or annually

29
Q

Natural factors effecting hydrograph

A

size of basin
- larger basins catch more water, high peak
- smaller basins have less distance, shorter lag time

shape of basin
- circular basins are flashier, all point in watershed similar distance, water reaches river at same time
- long narrow basins, less flashy

steepness - topography
- flows quicker downhill, short lag time
less time to infiltrate, runoff higher

rock and soil type
- impermeable rocks reduce infiltration, more runoff, increase peak discharge, decreased lag time

30
Q

Human factors effecting hydrograph

A

Farming
- ploughing increases infiltration = less discharge, increased lag time
- livestock compact soil - more runoff, decreased lag time

Deforestation
- less interception = higher discharge
- more runoff - shorter lag time, more discharge

Urbanisation
- impermeable surfaces - increase runoff, higher discharge and decreased lag time

Water abstraction
- water stores in aquifers depleated, less water in channel so lower peak discharge

31
Q

what is a river regime?

A

annual hydrograph

show river discharge over a year
- show patterns and seasonal variations

show peaks and lows
influenced by temperature, vegetation etc

32
Q

physical factors that affect water cycle

A
  • storms and precipitation
  • seasonal changes
  • vegetation
33
Q

human activities that affect water cycle

A
  • farming practises
  • deforestation
  • urbanisation/ land use change
  • water abstraction
  • climate change
34
Q

how do storm events affect the water cycle

A

intense storms mean more precipitation - greater peak discharges

more surface runoff, infiltration to slow/ soil saturated

arger input of water into system

drought also has impacts
- reduced water storage in rivers and lakes
- less vegetation so less interception
- groundwater stores important

35
Q

how do seasonal changes affect the water cycle

A

affects size of inputs flows and stores

in winter
- reduce size of flows
- increased storage in cryosphere
- larger flows and stores as ice melts

most plants vary by season
- more plants in summer, more interception
- increased lag time (less runoff)
- decreased peak (more outputs)
- more evapotranspiration

summer - dry soils, less rainfall = runoff
winter - more rain, saturation = runoff

36
Q

how do farming practises affect the water cycle

A

affect infiltration

increase infiltration/ reduce runoff:
- ploughing, break up soil
- crops, increase infiltration and interception

decrease infiltration/ increase runoff:
- livestock, compact soils
- irrigation, not all water can infiltrate fast enough
ground water/ river levels fall if water abstracted from them

37
Q

how does deforestation affect the water cycle

A

reduces interception
- increase runoff
- exposed to soil erosion

less evapotranspiration
- less moisture returned to atmosphere
= decine in regional rainfall

38
Q

how does urbanisation affect the water cycle?

A

impermeable surfaces
- reduced infiltration and increased runoff

deforestation
- less evapotranspiration

39
Q

how does water abstraction affect the water cycle

A

more water taken from stores, reduces volume = depleated
(to meet demands for people)
eg lakes, rivers, and groundwater

rate of recharge slower than rate of use

dry seasons increase abstraction
- needed for consumption and irrigation, depleted more

40
Q

how does climate change affect the water cycle?

A

reduces storage in cyrosphere
- melts and enters hydrosphere
= sea level rise

wetter areas wetter and drier drier
- impacts farming and yeilds

more freuqent/ intense storms
- more precipitation inputs

increased temperatures = more evaporation
- more water vapor in atmosphere

41
Q

Outline dynamic equilibrium in the water cycle

A

Tendency for a natural state of balance within the water cycle
Global cycle is a closed system, no input or outputs, just recycled
Drainage basin has inputs (precipitation) and outputs (discharge and evaporation)
Storm events and human activity can disrupt equilibrium

42
Q

Relationship between water and carbon in atmosphere

A

Carbon dissolved in water = acid rain, leads to ocean acidification
Water vapour and carbon dioxide released in volcanic eruptions
Increased carbon in atmosphere leads to global warming which increases evaporation
And therefore precipitation

43
Q

Why is the water cycle important for life

A
  • Provides habitats in solid forms eg Antarctic animals
  • And liquid forms eg oceans
  • Liquid water to drink, can be used as fuel
  • water vapour in atmosphere used in photosynthesis, needed for plant growth on land and in sea and releases oxygen
44
Q

Percentage of water in spheres

A

69% freshwater in cryosphere
0.3% liquid in hydrosphere
0.04% water vapour in atmosphere

45
Q

what causes change to water balance?

A

farming
deforestation
mining

46
Q

physical factors affecting flood risk

A

heavy/antecedent rainfall
(rainfall before)
soil saturated = more runoff

geology - impermeable rock increases surface runoff

shape/size of drainage basin

47
Q

human factors affecting flood risk

A

deforestation
- reduced interception
- more runoff

farming
- compact soil = more runoff
- leads to deforestation

land use change
- urbanisation = impermeable surfaces
- more runoff

48
Q

what is an aquifer?

A

water infiltrates ground and collects in spaces in porous rocks
eventually becomes saturated

flows slowly through spaces

49
Q

stores in global water cycle

A

water vapour in atmosphere
surface storage
interception storage
ice/snow
oceans
groundwater stores - water stored in porous rocks

50
Q

how do magnitude of stores vary?

A

over time
- seasonal
- glacial/ interglacial

over scale
- local (drainage basin)
- global

51
Q

factors affecting infiltration rates

A

level of saturation

compacted or frozen = less

relief, steeper = flows before it can infiltrate

vegetation cover = less, interception and evapotranspiration

52
Q
A