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EV11001 > Hydrology > Flashcards

Hydrology Flashcards

1
Q

Why is water our most precious resource

A

supports all life on earth, limited supply

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2
Q

what un sustainanle development goal is water linked to

A

sdg 6 clean water and sanitation

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3
Q

what are sdg6 key goals

A

safe drinking water, adequate sanitation, good water quality, sustainable water use, resource management and protect ecosystems

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4
Q

What type of bonding does water form

A

hydrogen bonding and is extremely polar

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5
Q

Why is water a universal solvent

A

capable of dissolving more substances than any other liquid, only if H bonds can be overcome- if not precipitate forms

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6
Q

Hydrophillic

A

can dissolve in water

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7
Q

Hydrophobic

A

cannot dissolve in water

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8
Q

Density of water

A

only common liquid that expands when frozen, ice is 90% of that of water

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9
Q

What is the specific heat capacity (of water)

A

the energy required for a particular change in temperature 4.186 J g-1 c-1
-> high so water respinds to changes in air temp slowly

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10
Q

What is the specific latent heat

A

the energy required for a particular change in state
333.4 Jg-1 to melt ice without changing its temperature
2462 Jg-1 to evaporate water without changing its temperature

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11
Q

What is surface tension

A

the surface of a liquid to resist external force

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12
Q

Property of waters surface tension

A

due to fewer molecules at waters surface they cling to each other stronger making a strong barrier between water and the atmosphere

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13
Q

What is a rivers cathcment

A

the area around a river where precipitation will flow to that river, used to study the hydrological cycle of a river

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14
Q

What is the boundary between two cathchments known as

A

watershed

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15
Q

What makes up a hydrological cylce

A

inputs, stores and outputs

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16
Q

What is the equation to measure catchment water balance

A

P=Q+ET+L+⯅S
P= catchment precipitation
Q= catchment runoff
ET= catchment evapotranspiration
L= catchment leakage
⯅S= change in catchment storage
over time inputs must balance outputs plus increase in storgae

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17
Q

Application of water balances

A

decisions to manage water resources in a catchment
eg HEP, irrigation, resourvoirs, risk assessments for flooding etc

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18
Q

What is an event hydrograph

A

how catchment responds to a specific event eg storm

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19
Q

what is an annual hydrograph

A

plots the traditional water year, oct-sep

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20
Q

Why is the water year oct-sep

A

to account for spring melt, so all water measured actually fell within water year

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21
Q

What is a flashy hydrograph

A

one with lots of peaks due to responses to lots of extreme weather events

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22
Q

What is the lag time

A

the time between peak rainfall and peak river discharge- can be controlled by elements of catchment
eg urban with no infiltration have short lag time

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23
Q

Elements of a hydrogrpah

A

discharge -> base flow, rising and falling limb, peak discharge
rainfall- peak rainfall

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24
Q

What are the three categories of weather

A

precipitation
obscurations(any phenomena in atmosphere that reduces visibility vertically)
other phenomena(wind related)

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25
Q

What is precipitation

A

any form of water particle, whether liquid or solid, that falls from the atmosphere and reaches the ground

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26
Q

Characterisation of rain

A

drops larger that 0.5 mm, or if smaller are separated

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27
Q

Characterisation of drizzle

A

uniform precipitation made of fine drops close together, appears to ‘float’

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28
Q

Characterisation of snow

A

branched and in the form of six-pointed stars.​

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29
Q

Characteristion of snow grains

A

very small, white, and opaque grains of ice. Basically, this is frozen drizzle

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30
Q

Characterisation of ice crystals

A

falling crystals of ice in the form of needles, columns, or plates. Also called ‘diamond dust’, ice crystals appear like fog with individual water particles forming directly as ice

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31
Q

Characterisation of ice pellets(sleet)

A

transparent or translucent pellets of ice, which are round or irregular hard grains of ice consisting of frozen raindrops, or largely melted then refrozen snowflake

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32
Q

Characterisation of hail

A

small balls or other pieces of ice falling separately or frozen together in irregular lumps. Associated with thunderstorms, individual hail stones are ¼ inch (5 mm) or greater in diameter

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33
Q

What are forms of condensation

A

fog, mist, dew, clouds

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34
Q

What is condensation

A

the process where water vapor becomes liquid

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35
Q

What are the ways condensation happens

A

air becomes so saturated with vapor that it cannot hold anymore
air is cooled to its dew point

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36
Q

What is dew point

A

the temperature at which condensation happens​

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37
Q

What is relative humidity

A

The relationship of how much water a given mass of air actually holds compared to the amount it can hold

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38
Q

What affects airs ability to hold water

A

temperature eg 20c water can hold 2x as much than at 10c
hot air expands and rises
cold air contracts and sinks

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39
Q

When is air said to be saturated

A

When air holds as much water vapor as it can for a given temperature (100% relative humidity)

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39
Q

Nimbostratus characteristics

A

continual precip that lasts for hours, low lying and full of moisture

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40
Q

What are the two clouds that bring precipitation

A

nimbostratus and cumulonimbus

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40
Q

What are condensation nuclei

A

they provide a surface for water to condense on
very small particles eg dust, pollen, salt spray

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41
Q

Cumulonimbus characteristics

A

produce rain thunder and lightning, occur at cold fronts

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42
Q

How is precipitation formed

A

particles are uplifted, dew point is low so ice crystals form, crystals combine to make larger flakes, process continues until flake is so heavy it falls and melts to form raindrops

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43
Q

What is cyclonic uplift

A

Cyclonic precipitation is caused by the lifting of an air mass because of the pressure difference
If low pressure occurs at an area, air will flow horizontally from the surrounding area, causing the air at the low-pressure area to lift

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44
Q

What are the two types of cyclonic precipitation

A

frontal- differences between warm and cold fronts
non frontal- warm air is stationary and cold air meets it

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45
Q

What are the characteristics of a cold front

A

cold air mass drives out a warm air mass​
Intense precipitation in comparatively small area​

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46
Q

What are the characteristics of a warm front

A

warm air mass replaces the retreating cold air mass​
Less intense precipitation but is spread over a comparatively larger area​

47
Q

What is convective uplift

A

occurs in equatorial areas
surface is heated by the sun, air rises and cools then reaches its saturation limit to form precipitation
results in intense short lived rainfall events

48
Q

What is orographic uplift

A

moist air mass meets physical barriers causing air to rise up, condense and precipitate
rain concentrated on windward side of barrier-> leads to rain shadow

49
Q

What areas of the planet receive the most precipitation

A

those with convergent air masses
eg at equator, 60*

50
Q

Characteristics of cyclonic rainfall

A

covers extensive areas but with local intense cells
lead to regional flooding and highest daily falls in uk

51
Q

Characteristics of convective rainfall

A

very intense but localised and short lived
can generate flash floods

52
Q

What are the three temporal patterns of measuring rainfall

A

long term- average conditions
medium term- seasonal, irrigation schedules
short term- forcasting

53
Q

What is evapotranspiration

A

the sum of all processes by which water moves from the land surface to the atmosphere via evaporation and transpiration

54
Q

What is evaporation

A

Vaporisation of liquid water into water vapour. Water moves from the Earth’s surface to the atmosphere

55
Q

What is transpiration

A

Evaporation of water from plants occurring at the leaves

56
Q

What are the three requirements for evaporation to occur

A

water available at surface​

unsaturated air​

energy supply​

57
Q

What are the two main types of energy supply for evaporation

A

net radiation- energy available due to the balance of incoming and outgoing radiation​
sensible heat- energy transferred from a warmer body to a cooler one, e.g. transfer of energy from air to cooler water on ground surface​

58
Q

When does transpiration occur

A

when the plant leaves its stomata open for photosynthesis

59
Q

What is potential evapotranspiration (PE)

A

The maximum amount of water that would be evapotranspired if enough water were available (from precipitation and soil moisture). ​

60
Q

What is actual evapotranspiration (ET)

A

The actual amount of water which is evapotranspired and is limited by the amount of water that is available
ET will always be less than or equal to PE

61
Q

How to measure evaporation

A

lysimeters

62
Q

What is a lysimeter

A

water tight tank containing soil and plants growing in the same field
Evapotranspiration is estimated in terms of the amount of water required to maintain constant moisture conditions within the tan

63
Q

What are the two methods for estimating evapotranspiration

A

thornthwaite
penman monteith

64
Q

What are the factors that effect evapotranspiration

A

temperature- air is warmer rates go up, warm cause stomata to open
water availability
energy availability
humidity gradient
wind speed
physical attributes of vegetation- height, leaf area
stomata resistance
soil characteristics- clay hold water

65
Q

What is the water table

A

The boundary between the unsaturated zone and the saturated zone underground

66
Q

What is groundwater

A

The water found underground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations of soil, sand and rocks called aquifers

67
Q

What is an aquifer

A

A body of rock and/or sediment that holds groundwater​

68
Q

What is infiltration

A

The flow of water from aboveground into the subsurface

69
Q

What is percolation

A

The downward movement of water through the soil

70
Q

What is capillary rise

A

upward movement of water during periods of moisture deficit (dry periods)​

71
Q

What is infiltration capacity

A

The maximum rate at which a soil in any given condition is capable of absorbing water.​

72
Q

What does the infiltration capacity regulate

A

determining whether streamflow is derived from the surface (overland flow) or the sub-surface (throughflow)

73
Q

What is the infiltration rate

A

The rate at which the water actually infiltrates through the soil during a storm

74
Q

What happens when rainfall intensity is greater than the infiltration capacity

A

rainfall excess occurs and infiltration excess overland flow occurs

75
Q

What happens to the infiltration capacity as the moisture content of soil increases

A

decreases

76
Q

What factors effect infiltration rates

A

storm characteristics
land surface condition
soil characteristics
vegetation cover
surface soil and water temperature

77
Q

What is hydraulic conductivity(K)

A

term used to describe how easily fluid moves through a porous medium

78
Q

What is saturated fluid conductivity(Ksat)

A

when all pores are full of water

79
Q

When does groundwater move vertically

A

the unsaturated zone

80
Q

When does groundwater move horizontally

A

the saturated zone

81
Q

What is the capillary fringe

A

a zone in the soil just above the water table that remains saturated or almost saturated, because the water is drawn up against the force of gravity due to waters adhesive and cohesive forces (capillary action)

82
Q

Aquifer characteristics- porosity

A

fractional volume occupied by pores(hold) ie spaces between particles

83
Q

Aquifer characteristics- permeability

A

capacity for water throughput(yield) ie can water pass through pores

84
Q

What is a confined aquifer

A

surrounded by nonpermeable substance

85
Q

What is an unconfined aquifer

A

not surrounded so water can leave

86
Q

What is a perched aquifer

A

local importance only
impermeable rock above water table that water sits above

87
Q

What is direct(percolation) groundwater recharge

A

rainfall or snowmelt leads to widespread infiltration of soil and then vertically down to groundwater​

88
Q

What is indirect groundwater recharge

A

input translated first to overland flow or streamflow, but reaches groundwater in areas of locally high permeability ​

89
Q

What is hydraulic head

A

water flowing from areas of high to low gravitational potential

90
Q

What is managed groundwater recharge

A

in times of surplus the aquifer is artificially recharged and used in times of shortage

91
Q

Define a flood

A

an overflow of a large amount of water beyond its normal limits, especially over what is normally dry land

92
Q

What is a river(fluvial) flood

A

flood from river to a flood plain

93
Q

what is a flash flood

A

intense rainfall over a short period of time

94
Q

what is surface(pluvial) flooding

A

urban areas with overwhelmed drainage

95
Q

what is a coastal(tidal) flood

A

changes in climate cause sea levels to change and storm conditions to arise

96
Q

What is groundwater flooding

A

infrastructure built low down and water rises

97
Q

What causes flooding

A

precipitation intensity, duration, and extent

98
Q

what is the return period of a flood

A

average interval between exceedence of some threshold eg 1 in 200 year flood

99
Q

what is the annual probability of a flood

A

estimated probability of a flood happening in a given year

100
Q

what is a frontal system in a flood

A

prolonged, low-moderate intensity, dangerous when stationary

101
Q

What is convective rainfall in a flood

A

localised, short duration, high, intensity, enhanced over hills and urban areas, summer seasonality

102
Q

What are factors that intensify flooding

A

frozen, compacted or parched ground
degree of saturation
impermeable surfaces
land management changes

103
Q

What is a meteorological drought

A

extended period of dry weather

104
Q

What is a hydrological drought

A

water supply starts to fall below normal

105
Q

What is an agricultural drought

A

water shortage damages cropss

106
Q

what is an ecological drought

A

widespread ecological damage due to lack of water

107
Q

what is a socioeconomic drought

A

water supply affects supply/demand commodities

108
Q

What is the standardised precipitation index

A

a drought indice used to characterise a drought in the uk

109
Q

What factors affect the severity of a drought

A

duration
accumulated deficit
mean deficit
maximum intensity

110
Q

What does the term water quality refer to?

A

the biological, physical and chemical properties of water

111
Q

What does biological water quality measure

A

diversity and abundance within a given stretch of river of fish, invertebrates , macrophytes and algae

112
Q

What does morphological water quality measure?

A

the physical structure of the river and issues of river continuity​ for river straightening, culverting, impounding and substrate manipulation

113
Q

What does phsiochemical water quality measure?

A

measuring concentration or level at a specific point on the river
eg pH nutrients oxygen tmep sediment emerging pollutants

114
Q

What is point pollution

A

Where the source directly enters the water body at a specific point​

115
Q

What is diffuse pollution

A

Where the source enters the water body through the landscape​

116
Q

What is eutrophication

A

The enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned

EV11001 (2 decks)

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