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A-Level Geography > Topic 5 - EQ 1 > Flashcards

Topic 5 - EQ 1 Flashcards

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1
Q

What is the global hydrological cycle?

A

The process of water being evaporated, and then condensing as clouds, before falling again as precipitation onto land and water. The cycle then repeats itself

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2
Q

What is the cyrosphere?

A

Areas of earth where water is stored as snow or ice.

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3
Q

What is residence time?

A

Residence time is the amount of time that water stays in a specific place before it evaporates back up into the atmosphere.

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4
Q

What’s a closed system?

A

when there is a transfer of energy but not matter between the system and it’s surrounding. There are no external inputs/outputs, any inputs come from within the system

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5
Q

What are flows (fluxes)?

A

measurements of the rate of flow between stores

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6
Q

What are processes?

A

the physical mechanisms such as evaporation that drive the flows of water between the stores

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7
Q

What are stores? (Stocks)

A

reservoirs where water is held, e.g. oceans

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8
Q

What is blue water?

A

water that is stored in rivers, streams, lakes and groundwater in liquid forms (visible)

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9
Q

What is green water?

A

water stored in the soil and vegetation (invisible)

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10
Q

What is the ocean - atmosphere flux?

A

The rate at which the flow of water between the ocean and atmosphere takes place. 400,000km^3/year go from ocean to atmosphere, and 370,000km^3/year goes from the atmosphere to the ocean.

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11
Q

What is the land atmosphere flux?

A

The rate at which water flows between the land and the atmosphere. 60,000 km^3/year goes from land to atmosphere, and 90,000 km^3/year goes from atmosphere to land. 30,000 km^3/year of water on land is transferred to the oceans.

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12
Q

What is the residence times of oceans? What % of global water does it make up?

A

3600 years, makes up 96.9% of total global water.

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13
Q

What is the residence time of the cryosphere? What % of global water does it make up?

A

15,000 years, makes up 1.9% of the total global water.

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14
Q

What is the residence time of terrestrial areas?

A

1 week - 10,000 years.

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15
Q

What is the residence time of the atmosphere? What % of global water does it make up?

A

10 days, atmosphere makes up 0.01% of total global water.

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16
Q

What percent of total water is freshwater?

A

Only 2,5% of the total global water is freshwater. This is the amount needed for life to survive. However, technology is being used to extend the availability of freshwater supplies, for example by desalination of ocean water.

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17
Q

How much of the total fresh water is actually accessible to us?

A

Only the 1.2% which is surface/other types of freshwater. The rest is ground water (30.1%) and glaciers/ice caps (68.7%). This 1.2% we can use is only 0.03% of the total global water.

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18
Q

What can we actually use of the surface freshwater?

A

69% of this surface water is ground ice/permafrost. However we cannot extract water from frozen soil or mountain sides, so this is inaccessible as well. As a result, we can only use the other 31% (and 0.084% of total water). This mainly comes from rivers, lakes and soil etc. These can however be isolated locations and difficult to extract from.

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19
Q

What is the definition of precipitation?

A

The movement of water in any form from the atmosphere to the ground.

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20
Q

What is evaporation?

A

The change in state of water from a liquid to a gas.

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21
Q

What is fossil water?

A

Ancient, deep groundwater from former pluvial (wetter) periods. It can stay for over 10,000 years beneath the earths surface, as it currently is in the Sahara dessert and used for potato farming in many locations.

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22
Q

What is a systems approach?

A

Systems approaches study the hydrological phenomena by looking at the balance of inputs and outputs, and how water is moved between stores and flows.

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23
Q

Why do stores such as soil moisture and small lakes and rivers have small residence times?

A

It is spread very thinly across the earths surface, so it is easily lost to other stores by evaporation.

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24
Q

What is the catchment?

A

This is the area of land drained by a river and it’s tributaries

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25
Q

What is a watershed?

A

The highlands which divides and separates waters flowing to different rivers.

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26
Q

What percent of total global water is in rivers?

A

0.007%, which is the main source of surface water for humans,

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27
Q

What are the two processes which drive the global hydrological cycle?

A

Solar energy and gravitational potential energy (GPE). More evaporation occurs as the global climate warms, which then increases moisture levels in the atmosphere. This leads to increased condensation as the air cools, and greater precipitation.

GPE keeps water moving through the system in a sequence of inputs, outputs stores and flows.

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28
Q

What type of system is the global hydrological cycle?

A

This is a closed system which is driven by solar energy and gravitational potential energy. It is a closed system as there’s a fixed amount of water in the earth (roughly 1385million km^3). As a closed system has no external inputs or outputs, this total volume of water is constant and finite.

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29
Q

What is a real example of how global water is held in different states (and this varies)?

A

In the last ice age, more water was held in the cryosphere in solid forms as ice or snow, and less was held in oceans. Sea levels were 140m lower than today. However recent climate warming is reversing this with major ice losses in Greenland and Antarctica.

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30
Q

What percentage of total global water is groundwater?

A

1.1%

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31
Q

What percentage of total global water is in rivers and lakes?

A

0.01%

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32
Q

How is water stored on land?

A

It is stored in rivers, streams, lakes and groundwater in liquid form. It’s often known as bluewater, the visible part of the hydrological cycle. Water can, however, also be stored in vegetation of beneath the surface in the soil. This is known as green water and is the invisible part of the hydrological cycle.

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33
Q

How can some groundwater last 10,000 years before it evaporates?

A

Ancient groundwater is found deep below the Saharan Desert and they formed as a result of former pluvial (wetter) periods.

Major ice sheets (such as Antarctica and Greenland) also store ice for very long periods of time. The residence time of some Antarctic ice is over 800,000 years.

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34
Q

What is a drainage basin?

A

The area of land drained by a river and its tributaries.

Drainage basins can be of any size, from that of a small stream possibly without tributaries up to a major international river flowing across boarders of several countries.

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35
Q

What are all the stores in a drainage basin?

A

-Interception storage
-Surface storage
-Soil water storage
-Groundwater store
-Channel store
-Vegetation store

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36
Q

What is the input into the drainage basin?

A

Precipitation

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37
Q

What are the outputs in the drainage basin?

A

-River discharge
-Evaporation
-Evotranspiration
-Transpiration

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38
Q

What are all the flows in the drainage basin?

A

-surface run-off
-throughflow
-soil throughflow
-Infiltration
-Percolation
-Groundwater flow
-River Channel flow

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39
Q

What is interception storage?

A

The storage of water when it lands on vegetation (or structures like buildings) before it reaches the soil. It is a temporary store before evaporation or stemflow

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40
Q

What is surface storage?

A

The storage of water on the surface including puddles, ponds and lakes

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41
Q

What is soil water storage?

A

The storage of water in soil. Water is held in the small gaps between soil particles

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42
Q

What is groundwater storage?

A

The storage of water in the ground rocks of permeable rock. The water is held in cracks (limestone) bedding planes (sedimentary rock) or pores (chalk). Rocks with lots of water storage are called aquifers

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43
Q

What is the channel store?

A

The storage of water in the river channel. As water is being transported to the sea it is a store of water

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44
Q

What is the vegetation store?

A

The storage of water in the vegetation. Plants and trees take up water through their roots and water is stored here.

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45
Q

What is surface runoff?

A

The horizontal flow of water over the surface of the land either in little channels or over the whole surface – this is usually a quick flow.

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46
Q

What is precipitation?

A

The input into a drainage basin system. It includes all forms of moisture entering: hail, snow, dew, frost, sleet and rain.

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47
Q

What is throughfall?

A

The downwards flow of water moving downwards from interception storage to the surface

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48
Q

What is soil throughflow?

A

The horizontal flow of water moving through soil (between the particles) towards the river

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49
Q

What is infiltration?

A

The downwards movement of water from the surface into the soil.

50
Q

What is percolation?

A

The downwards movement of water from the soil to the permeable ground rock

51
Q

What is groundwater flow?

A

The horizontal movement of moving through the rocks (cracks/bedding planes/pores) slowly towards the river. This is the movement of water below the water table sideways to the river.

52
Q

What is river channel flow?

A

The movement of water in the river channel moving towards the sea.

53
Q

What is evaporation?

A

The output of water when water is heated and turned from a liquid into a gas

54
Q

What is transpiration?

A

The output of water where moisture is taken into plants through their roots, moved to the leaves by capillary action and then evaporates from the leaves into a gas.

55
Q

What is evotranspiration?

A

The combined output of water from evaporation and transpiration

56
Q

What is river discharge?

A

The output of water from a river channel out to sea.

57
Q

What is condensation?

A

The change from a gas to liquid, such as when water vapour changed into water droplets.

58
Q

What is the dew point?

A

The temperature at which dew forms (temp which water droplets begin to condense). It is a measure of atmospheric moisture.

59
Q

What conditions are needed for precipitation?

A

-Air cooled to saturation point with relative humidity of 100%
- Condensation nuclei, such as dust particles, to facilitate the growth of droplets in clouds.
-Temp below dew point.

60
Q

What are the 5 precipitation factors that affect the drainage basin?

A

-The amount of precipitation
-The type of precipitation e.g snow can act as a temporary store
-Seasonality, seasonal rainfall has huge impacts on physical processes operating in the drainage basin.
-Intensity of precipitation
-Distribution of precipitation within the basin, particularly noticeable in big drainage basins such as the Nile, where tributaries start in different climatic zones.

61
Q

What are the three types of rainfall?

A

-Conventional rainfall
-Frontal (cyclonic) rainfall
-Relief (orographic) rainfall

62
Q

Which drainage basins are particularly prone to orographic and frontal rainfall?

A

The western side of the UK. North-west UK such as Cumbria can receive over 2000mm of rainfall a year, making them prone to saturate surfaces, high water tables and antecedent moisture. This makes flooding more likely.

63
Q

Which drainage basins receive more precipitation from convectional rainfall?

A

Drainage basins in East Anglia. These are much drier but in the summer months experience heavy rainfall bursts due to convection air instability. In these months the ground warms up, evaporation takes place and summer thunderstorms produce short bursts of heavy rain which can lead to flash floods.

64
Q

What is the rain shadow effect?

A

The eastern side of the UK receives less rain than the west, because the western hills force moist air to rise as it approaches the Atlantic - leading to orographic rainfall in the north and west.

65
Q

How does Orographic rainfall occur?

A

Warm moist air is forced to rise over high areas. The air cools and condenses forming clouds. Precipitation occurs. This air then descends and warms, leaving a rain shadow on the other side of the mountain peak.

This is in the west of the UK as warmer, moist Atlantic air rises over the western uplands. Heavy rain falls on western and northern parts of the UK.

66
Q

How does Convectional rainfall occur?

A

The sun first heats the land and the air above, this warm air rises, cools and condenses forming clouds. Rain the falls.

Typically, this is in the east and southeast of the UK during summer. This is due to periods of high temperatures. The rain is often intense and associated with electrical storms and thunder.

67
Q

How does frontal rainfall occur?

A

Warm air is forced to rise over cold air. Condensation occurs which leads clouds to form. It the rains heavily along the front (where warm air hits the cold air).

This brings the majority of the UK rainfall over the year. Fronts are formed as part of a low-pressure area when warmer moist air from the southwest meets colder polar air from the north or north west. Warmer air is forced to rise over the denser and colder air.

68
Q

How does vegetation + precipitation affect the rate of interception?

A

The rate of interception is dependent on two factors, the precipitation and vegetation. Interception is greatest when the precipitation is light and of short duration. This is because dry leaves and stems have the greatest water storage capacity.

For vegetation, denser types such as coniferous forests (intercepts 25-35% annual rainfall) will intercept more than sparser deciduous forests (15-25% rainfall). This is especially true when deciduous trees shed their leaves in winter. All forests however intercept more than grasses or crops (10-15% rainfall)

69
Q

How does wind affect interception?

A

Hugh winds are also bad for interception loss as wind displaces rain which causes evaporation to happen more quickly.

70
Q

What is interception loss?

A

This is water that is retained by plant surfaces and later evaporated or absorbed by the vegetation and then transpired

71
Q

What is infiltration capacity?

A

The maximum rate and which rain can be absorbed by a soil.

72
Q

How do andecendent conditions affect infiltration?

A

If the soil was already moist before, the soil will reach the point of saturation more quickly and therefore the infiltration rate will be lower.

73
Q

What happens to the infiltration capacity over time?

A

Infiltration capacity decreases with time through a period of rainfall until a more or less constant low value is reached.

74
Q

How does the soil texture affect infiltration?

A

Whether the soil is sand, silt, loam or clay influences soil porosity. Sandy soils have a higher infiltration capacity (3-12mm/hr) than less permeable clays (0-4mm/hr).

75
Q

How does vegetation cover affect the rate of infiltration?

A

Infiltration is far more significant in land covered by forests (50mm/hr) or moorland (42mm/hr) due to less risk of flooding from heavy rain. Tree cover can prevent soil for saturation and the infiltration rate falling. Permanent pasture has infiltration rates of 13-23 mm/hr depending on grazing density and soil type.

76
Q

How does the soil surface and structure affect infiltration?

A

The nature of the soil surface and structure is also important. Compacted surfaces inhibit infiltration (around 10 mm/hr), especially when rain splash impact occurs.

77
Q

How does slope angle affect infiltration rates?

A

Slope angle can be very significant. Very steep slopes tend to encourage overland run-off. Shallowing slopes however promote infiltration.

78
Q

What is saturated overland flow?

A

This occurs when water accumulates in the soil until the water table reaches or ponds on the surface, forcing further rainwater to run off the surface. This is most common with thin soils of moderate permeability. Concavities near a stream or riverbank often have high moisture levels and may produce saturated overland flow early in a rainstorm cycle.

79
Q

What is infiltration-excess overland flow?

A

Infiltration-excess overland flow occurs when the rainfall intensity exceeds the infiltration capacity. This causes excess water to flow over the ground surface.
Any surface runoff will quickly deliver water into the river channels, increasing the risk of flooding downstream.

80
Q

What happens when infiltrating water reaches permeable underlying bedrock?

A

It will continue to move slowly down into the rocks by percolation. This water fills the spaces between the rocks, creating groundwater storage and an aquifer. Thus will occur where the permeable layer lies above an impermeable layer, so that the water cannot percolate any further, creating a saturation zone. The upper level of this zone is called the water table. This water may move as groundwater flow if geological structure allows it.

81
Q

What does the rate of percolation and groundwater flow depend on?

A

It depends on the permeability of the rock, which is linked to its porosity or perviousness. Porosity is do to with the total volume of pore spaces. This is highest in coarse-grained rocks such as sandstone, pervious rocks like limestone have joints and bedding planes along which water can flow. This means groundwater flow and percolation increased with porosity and perviousness. Granite (an impermeable rock) will prevent percolation or water moment. Groundwater flow also depends on the angle of the rock strata, a steeper gradient allows gravity to operate more efficiently.

82
Q

Where is the highest precipitation input on earth?

A

In the tropics due to the ITCZ. I’m the ITCZ, intense solar radiation fuels the convection of warm, humid air. This results in condensation and precipitation.

The highest average annual rainfall is in Mawsynram, India with 11,873mm of rain per year. This is mostly in the monsoon season of June to September.

83
Q

Where is the lowest precipitation input on earth?

A

These are in stable areas of high atmospheric pressure. E.g Quillagua in the Atacama Desert. This is the driest place on earth, receiving less than 0.2mm of rain per year.

84
Q

What is field capacity?

A

At this point, the soil is full of water and cannot hold anymore.

85
Q

What is soil moisture surplus?

A

Precipitation is greater than potential evapotranspiration and the soil water store is full, so there is a surplus of soil moisture for plant use, run off into streams and recharging groundwater supplies. The soil is said to be at field capacity.

86
Q

What are maximum annual temperatures?

A

High temperatures can cause maximum evapotranspiration, precipitation is at a minimum and therefore plants use up the soil moisture store. River levels will fall and crops will need irrigation.

87
Q

What is soil moisture recharge?

A

This occurs when potential evapotranspiration decreases so that it is lower than precipitation, and the soil store starts to fill up again.

88
Q

What is soil moisture utilisation?

A

Potential evapotranspiration increases and exceeds precipitation, so there is more water evaporating from the ground surface and being transpired by plants than is falling as rain. Water is also drawn up from the soil by capillary action. The water is gradually used up.

89
Q

What is soil moisture deficiency?

A

The soil moisture store has been used up by high rates of evapotranspiration and low precipitation. Plants can only survive if they’re adapted to periods of drought or are irrigated.

90
Q

What is the water budget?

A

The water budget reflects the natural annual balance between the inputs and outputs in a given river area.

91
Q

What is the formula for the water budget?

A

P = Q + E +/- store change, where P = precipitation. Q = channel discharge. E = evapotranspiration.
Whatever falls as precipitation should be balanced by other components.

92
Q

What do water budget/balance graphs show?

A

Water Budget/Balance graphs provide a direct comparison of natural water supply and demand and the impact this has on soil water availability.
They help us identify where P>ET = positive balance (flood) and where P

93
Q

What is a river regime?

A

This describes the annual variation in the discharge of a river at one particular point. Many physics factors affect the river regime throughout the year, however they aren’t completely natural as the regimes are affected by activities in the river drainage basin.

94
Q

What factors affect the river regime?

A

-The size of the basin and where in the basin measurements are taken.
-The amount,pattern and intensity of precipitation.
-Temps experienced: evaporation will be marked in summer as the temperatures are warmer.
-The geology and overlying soils, especially their permeability and porosity. Groundwater store is slowly released into the river as base flow.
-amount + typed of vegetation cover
-Human activity e.g dam building.

95
Q

What is the river regime like in tropical areas?

A

In these areas, evapotranspiration tends to be stable (high) but summer rain causes a peak.

96
Q

What is the river regime like in rivers with glacier melt?

A

European mountain river have a high-water period when glaciers feeding them melt most rapidly.

97
Q

How do areas of snowmelt affect river regime?

A

Melting of snow cover either in mountainous areas during early summer or over the Great Plains of North America in spring. This causes a peak in discharge.

98
Q

How does oceanic rainfall/evapotranspiration affect river regime?

A

In many oceanic areas of Europe, rainfall is evenly distributed but high evapotranspiration in summer leads to low run-off.

99
Q

What factors affect river regime?

A

-Size of the river
-Amount/pattern/intensity of precipitation
-Temperature experienced
-Geology and overlying soils
-amount + types of vegetation cover
-Human activities

100
Q

How does the size of the river affect river regime?

A

Many large rivers have complex regimes, which come from varied catchments. It’s therefore also important where measurements in the basin are taken.

101
Q

How does amount, pattern and intensity of precipitation affect river regime?

A

The river regime often reflects rainfall seasonal maxima or when the snow fields or glaciers melt.

102
Q

How does geology and overlying soils affect river regime?

A

Especially with permeability and porosity, water is stored as groundwater in permeable rocks and is gradually released into the river as base flow. This tends to regulate the flow during dry periods.

103
Q

How does the amount and type of vegetation cover affect the river regime?

A

Wetlands can hold the water and release it very slowly into the system.

104
Q

What type of human activity affects river regime?

A

Dam building, which can regulate the flow of a river.

105
Q

What is potential evapotranspiration?

A

The water loss that would occur if there was an unlimited supply of water in the soil for use of vegetation.

106
Q

What is the human impact on evaporation and evapotranspiration?

A

Key changes in global use (E.g deforestation) are a key influence. Deforestation reduces transpiration rates. However, artificial reservoirs (such as behind mega dams) cuts down surface storage and therefore increased evaporation.

107
Q

What is the human impact on precipitation?

A

Human activity can affect precipitation by cloud seeding. They use silver iodide pellets to act as condensation nuclei to attract water droplets. The aim is to increase rainfall in drought-strikes areas. It was also used in Beijing for 2008 Olympics to help clear pollution.

108
Q

What is the human impact on interception?

A

Interception is largely determined by vegetation type and density. Therefore, deforestation as well as afforestation both have significant impacts. Deforestation leads to increased surface run-off. This increases flooding potential and a decline in surface storage.

Although afforestation should do the opposite, it was seen in Wales that after afforestation occurred in the Catchment area of river Severn, there was increased runoff due to soil compaction from tractors.

109
Q

What is a real world example of the effects of deforestation?

A

Nepal, where deforestation led to dry soil due to increased surface runoff, as well as more sediment load further down stream. The rain drop impact causes soil compaction. So less soil could infiltrate leading to increase run-off.

110
Q

What is the human impact on infiltration and soil water?

A

Impacts on infiltration largely result from a change of land use. Infiltration is 5x greater on land under forests in comparison to grassland. Conversion to farmland means increased soil compaction, more overland flow and less infiltration.

While farming and grazing animals can cause soil compaction, ploughing increase infiltration by loosening the soil. If there’s poor drainage, water logging and salinisation can be common. Installing drainage helps to avoid this.

111
Q

What is the human impact on groundwater?

A

Human use of irrigation for certain types of farming has led to declining water tables, e.g in Texan aquifers. This irrigation reduces water flowing into rivers, and then as a result less water reaches oceans.

Many British cities have been affected by reduction in irrigation, groundwater levels began to rise and other issues such as surface water flooding became big issues, with flooding increasing in cellars and basements as well as London Underground tunnels.

112
Q

What issues has deforestation caused in Amazonia?

A

Twenty percent of the forest has been destroyed to make room for agricultural and cattle farming, as well as towns and roads.

Not only does this affect the atmosphere, as trees act as the lungs of the earth, but there is also an enormous impact on water cycling. Usually in a forest 75% of intercepted water is returned to the atmosphere by evapotranspiration. However, this reduces to 25% with deforestation. This leads to a drier climate, which can cause droughts and even make forest fires more likely.

Water run-off can also however cause flooding, and surface runoff causes soil erosion which can lead to a lack of soil nutrients.

113
Q

What is a storm hydrograph?

A

This is a graph showing variation in discharge (volume) of water at a given point over a short period of time, normally an individual storm (few days).

114
Q

What is bankfull discharge on a storm hydrograph?

A

This is the point where the river is as full as it can be (up to the top of river banks) before it begins to flood with any more water.

115
Q

What is the baseflow/groundwater flow on a storm hydrograph?

A

This represents the normal day to day discharge a river will experience and how it changed this the groundwater slow slowly entering the river.

116
Q

What are the factors effecting river regime?

A

-Humans
-Vegetation
-Geology and soil
-Size of river
-Temperature
-Precipitation

117
Q

What is the storm hydrograph of a ‘flashy’ river like?

A

Short lag time, high peak, steep rising limb.

118
Q

What is the storm hydrograph of a ‘flat’ river like?

A

Long lag time, low peak, gently sloping rising limb.

119
Q

What is the base flow on a storm hydrograph?

A

The normal, day-to-day discharge of the river.

120
Q

What geographic factors cause a ‘flashy’ river?

A

-Intense rain, exceeding infiltration capacity or rapid snow melt
- Impermeable rock e.g Granite
- Low infiltration rate e,g clay soils
- Steel relief
- Small basins
- Circular basins
- Low density vegetation, little infiltration.
- Wet antecedent conditions
- Urbanisation.

A-Level Geography (27 decks)

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