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CIVL3141 > Weeks 1&2 > Flashcards

Weeks 1&2 Flashcards

1
Q

What are the primary issues regarding water?

A

Too much (flooding); too little (drought); too dirty (contamination)

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2
Q

What percentage of global water is fresh & easily accessible?

A

2.5%

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3
Q

What are the key aspects of the Hydrologic Cycle? (Hint: there are 8)

A

Precipitation, evaporation, transpiration, sublimation, infiltration, percolation, runoff, and groundwater table

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4
Q

What are the key flow processes within the Hydrologic Cycle?

A

Precipitation, interception by vegetation, storage in depressions, infiltration into soil surface, interflow, groundwater flow

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5
Q

What is runoff?

A

Runoff is surface water flow formed by precipitation that does not infiltrate

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6
Q

What is depression storage?

A

Depression storage is water that is held in puddles or small depressions

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7
Q

What is interflow? What are two other names for it?

A

Interflow is lateral movement of water through shallow surface soils. It is also known as subsurface lateral flow, or through flow.

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8
Q

What is sublimation?

A

Sublimation is the transition of water from solid phase directly to gas phase (ice to vapour)

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9
Q

What is the basic water balance equation? What does each term mean?

A 
dS/dt = I(t) - Q(t)
S: total storage within system
dS/dt: change in storage with time
I(t): flow into system w.r.t. time
Q(t): flow out of system w.r.t. time
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10
Q

Name the main types of water storage systems (from shortest to longest residence times).

A

Atmospheric, biological systems, rivers/streams, lakes/reservoirs, oceans, groundwater, ice / polar caps

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11
Q

Name the main types of inflows I(t).

A

Precipitation, surface inflows, subsurface inflows (groundwater)

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12
Q

Name the main types of outflows Q(t).

A

Evaporation, evapotranspiration, surface outflow, subsurface outflow (groundwater), diversions, human consumption

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13
Q

What is the discrete form of the basic water balance equation?

A

dS = S(t+dt) - S(t) = I dt - Q dt

where dt = time step

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14
Q

What is a catchment?

A

A catchment is a geographical structure in which water drains from elevated boundaries down to low points (known as catchment outlet)

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15
Q

How do you define a catchment boundary?

A

Starting at the catchment outlet, cross each ascending contour line at 90 degrees, until it reaches the highest point. Then pass through the centre line of this contour until the next downhill contour line. Continue to pass through these descending contours at 90 degrees until it reaches the outlet again. Check result by conducting droplet tests at various points within and just outside the catchment area.

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16
Q

What are sub-catchments, and what is their purpose?

A

Sub-catchments are divisions of a catchment area. The runoffs from each sub-catchment are combined and used in basic water balance calculations.

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17
Q

What is a topographic catchment boundary?

A

A topographic boundary divides the catchment area according to topographic high points

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18
Q

What is an effective/phreatic catchment boundary?

A

An effective boundary divides the catchment area according to subsurface borders & phreatic layers

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19
Q

What is evapotranspiration?

A

Evapotranspiration the transfer of water as vapour from near the earth’s surface to the atmosphere. It includes evaporation from water bodies, transpiration from vegetation, sublimation of snow & ice, and the transfer of water vapour directly from a soil surface.

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20
Q

What is precipitation?

A

Precipitation is atmospheric water that falls under gravity onto the earth’s surface, including drizzle, rainfall, snow, hail and dew.

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21
Q

What is infiltration?

A

Infiltration is the process of water penetrating the upper layers of soil, and then flowing vertical downwards into soil and subsoil

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22
Q

What is percolation?

A

Percolation is the vertical movement of water into deep soil towards water table or phreatic layer

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23
Q

What makes a system ‘sustainable’?

A

A sustainable system is one that is able to meet the human demand requirements, but also ensures all other requirements are adequately addressed.

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24
Q

What is the equation for global water resources assessment, and what does each variable mean?

A 
W = P x A x T
W: water use [km^3]
P: population [no. of people]
A: affluence [$/person]
T: water intensity [km^3/$]
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25
Q

What are some key considerations for sustainable water supply system in SEQ?

A

Population growth, climate, water efficiency, current & potential water supplies, ecosystem health, cost, social outcomes

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26
Q

What is used to assess ‘sustainability’?

A

Sustainability assessments are conducted using basic water balance equations

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27
Q

What is the key driver of global weather?

A

Solar radiation is the key driver of global weather

28
Q

What does uneven distribution of solar radiation result in?

A

Differential heating, which drives atmospheric convection cells

29
Q

Describe the basic convection cell.

A

Cool, dry air at a low pressure in the atmosphere creates a high pressure beneath it, causing the air underneath to subside, condense & warm, turning into warm, dry air. This air moves towards a low pressure area, picks up moisture & heat from the earth’s surface, and becomes hot & wet. This air then expands, cools & rises to a high pressure area in the atmosphere and becomes precipitation/condensation. This then moves towards a low pressure area, and the whole process starts again.

30
Q

Explain the relationship between the sun’s radiation and its angle of incidence to the earth’s surface (ignoring tilt & seasonal variations).

A

Much more energy is received at the earth’s equator, as the angle of incidence here is 0 degrees. As the angle of incidence increases (moving towards the poles), the less of the sun’s energy is received.

31
Q

Describe the wind names and directions due to the earth’s rotation (looking straight on at Australia).

A

Top left corner: Westerlies (SW)
Bottom left corner: Westerlies (NW)
Bottom right corner: Trade winds (SE)
Top right corner: Trade winds (NE)

32
Q

What are the names and positions of the 3 convection cells?

A

Polar cell: cells either side of north & south pole
Ferrel cell: cells between polar & Hadley cells
Hadley cell: cells either side of equator

33
Q

What is a ‘cold front’?

A

A cold front is the interface between cold polar air moving towards the equator, and warm tropical air that is forced upwards by the cold air. It results in big temperature gradients, strong winds & thunderstorms.

34
Q

Which direction does a low pressure system spin?

A

Clockwise

35
Q

Which direction does a high pressure system spin?

A

Anticlockwise

36
Q

Describe a high-pressure system.

A

A high pressure system is anticyclonic. It involves air sinking in the centre of the system. It is unstable due to cold air heating up and becoming unsaturated. Over land, they result in dry weather & no clouds.

37
Q

Describe a low-pressure system.

A

A low pressure system is cyclonic. It involves air ascending at the centre of the system. This air cools as it rises and becomes saturated. It results in development of clouds and rain.

38
Q

What are teleconnections & teleconnection patterns?

A

Teleconnections are the apparent relationship between climate anomalies at large distances. Teleconnection patterns are a recurring and persistent, large-scale pattern of pressure and circulation anomalies that spans vast geographical areas.

39
Q

Name some teleconnections.

A

E.g. El-Nino Southern Oscillations (ENSO), Indian Ocean Dipole (IOD), North Atlantic Oscillation (NAO), Pacific-North American (PNA)

40
Q

What are two important teleconnections for Australia?

A

El-Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD)

41
Q

What is El Nino for Australia?

A

El Nino is the negative phase of the ENSO. It is associated with warmer & drier than average conditions.

42
Q

What is La Nina for Australia?

A

La Nina is the positive phase of the ENSO (opposite of El Nino). It is associated with wetter & cooler than average conditions.

43
Q

How often does the El-Nino Southern Oscillation pattern occur?

A

ENSO cycles every 4-7 years

44
Q

What is the Southern Oscillation Index?

A

The Souther Oscillation Index (SOI) gives an indication of the intensity and development of El Nino and La Nina events in the Pacific Ocean. SOI >6 indicates La Nina and SOI < 6 indicates El Nino.

45
Q

What is drizzle?

A

Drizzle is light uniform rainfall with droplets size 0.1-0.5mm in diameter.

46
Q

What is rain?

A

Rain is water droplets larger than 0.5mm in diameter.

47
Q

What do ‘light’ and ‘heavy’ refer to?

A

‘Light’ & ‘heavy’ are measured of rainfall intensity.

48
Q

What is dew?

A

Dew is direct condensation of atmospheric vapour on the earth’s surface.

49
Q

What is ‘virga’?

A

‘Virga’ is precipitation that evaporates before reaching the earth’s surface.

50
Q

Why is fog not a form of precipitation?

A

Fog is not precipitation as the water drops are not large enough to fall to the earth’s surface.

51
Q

What is relative humidity?

A

Relative humidity the ratio of the actual vapour pressure to the saturated vapour pressure at a given temperature.

52
Q

What is the ‘dew point’?

A

The dew point is the temperature to which air must be cooled for it to become saturated. Precipitation occurs when air is cooled to near its dew point.

53
Q

Describe how clouds work?

A

Droplets form by condensation. They then ascend & grow from further condensation, become heavy enough to fall, and descend & shrink by evaporation. This cycle repeats over & over again until the droplets are heavy enough to fall to the ground.

54
Q

What are the steps in order for precipitation to occur?

A

The volume of air must become saturated. The vapour in this saturated air condenses due to sudden cooling. Droplets merge together until a large & heavy enough particle is created. This merging requires a condensation nucleus (e.g. dust or salt).

55
Q

What are the layers of the atmosphere, closest to furthest from the earth’s surface?

A

Troposphere, Stratosphere, Mesosphere, Thermosphere

56
Q

How is ozone gas formed? In which layer of the atmosphere is it formed?

A

Ozone is created in the mesosphere by the absorption of UV by oxygen. Oxygen (O2) splits and reforms with other oxygen molecule to create ozone (O3).

57
Q

What is orographic uplift?

A

Orographic uplift is when a moist air mass encounters a mountain range and is forced upwards. This air mass then cools, causing water vapour to condense, leading to precipitation.

58
Q

Describe a ‘cold front’? What type of clouds does it form?

A

In a cold air front, warm moist air is forced sharply upwards, and often generates storms & heavy precipitation. It forms cumulonimbus clouds (as well as cirrus, altocumulus & stratocumulus).

59
Q

Describe a ‘warm’ front’? What type of clouds does it form?

A

A warm front tends to slide over the top of a cold air mass. Precipitation is more wide-spread but less intense. It forms nimbostratus clouds (as well as cirrostratus & altostratus).

60
Q

How is precipitation measured?

A

Precipitation is measured as the vertical depth that would accumulate on a flat level surface if it were to remain where it fell.

61
Q

Describe the Thiessen polygon method of calculating rainfall.

A

Draw lines between all adjacent stations. Bisect these lines at 90 degrees. Extend these bisecting lines to form polygons. Calculate the weighted rainfall average by taking the sum of each area x rainfall, divided by the sum of the areas.

62
Q

What is evaporation?

A

Evaporation is the transfer of water vapour from a water surface to the air.

63
Q

What is transpiration?

A

Transpiration is the release of water vapour by plants through their leaves.

64
Q

What is the equation for latent heat of vaporisation and what are the units of each variable?

A

lambda = 2.50025 - 0.002365 T
lambda [MJ/kg]
T [degrees Celsius]

65
Q

What is latent heat of vaporisation?

A

Latent heat of vaporisation is the energy required to overcome equilibrium between a water body & the atmosphere (continuous transition between evaporation & condensation) i.e. the energy required to fully evaporate water body.

66
Q

What are the angles of arctic and antarctic poles?

A

66.5 degrees

67
Q

What are the angles of Tropic of Cancer and Tropic of Capricorn?

A

23.7 degrees

CIVL3141 (10 decks)

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