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Geography IGCSE > 1. Rivers > Flashcards

1. Rivers Flashcards

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1
Q

What is the hydrological cycle

A

The recycling of freshwater globally in a giant closed system. There is a fixed amount because water neither enters nor leaves the atmosphere

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2
Q

Name and explain water stores in the hydrological cycle

A
  • The atmosphere - where water exists as either water vapour or tiny droplets
  • The land in lakes, rivers and reservoirs
  • The sea where most is held in liquid form as well as ice
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3
Q

Name and explain water transfers in the hydrological cycle

A
  • Evaporation
  • Transpiration
  • Evapotranspiration
  • Condensation
  • Precipitation
  • Overland flow
  • Infiltration + percolation
  • Through flow
  • Groundwater flow
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4
Q

Evaporation

A

The hydrological cycle starts with evaporation due to the heat
of the Sun. Water is converted from a liquid into a gas (called water vapour).
This takes place from the surface of the sea and from water surfaces
(ponds and lakes) on land. Evaporation is particularly important in the
transfer of water from the sea store into the atmosphere.

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5
Q

Transpiration

A

plants take up liquid water from the soil and ‘breathe’ it into
atmosphere as water vapour.
Evapotranspiration - the loss of moisture from the ground by direct
evaporation from water bodies and the soil, plus transpiration from plants.

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6
Q

Condensation

A

The change in the atmosphere when water vapour cools
and becomes liquid. The liquid takes the form of water droplets that appear
in the atmosphere as clouds.

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7
Q

Precipitation

A

The transfer of water in any form (rain, hail or snow) from the
atmosphere to the land or sea surface.

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8
Q

Overland flow

A

Most precipitation that hits the ground moves due to gravity

and eventually enters a stream, river or lake. SURFACE RUN OFF

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9
Q

Infiltration and percolation

A

The transfer of water downwards through the

soil and rock into the aquifer or groundwater store.

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10
Q

Through flow

A

This takes place between the GROUND SURFACE AND GROUNDWATER STORE. As a result of gravity, water moves slowly through the soil until it reaches a stream or river.

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11
Q

Groundwater flow

A

This happens in the rocks of the aquifer and is the UNDERGROUND TRANSFER OF WATER to rivers, lakes and the sea.

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12
Q

What is a drainage basin

A
  • An open system in a relatively small area where water is collected and moved
  • Also has external inputs and outputs
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13
Q

What are some inputs of a drainage basin

A
  • Energy from the sun
  • Precipitation from moisture picked up from outside the basin
  • possibly water from tributary drainage basins
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14
Q

What are some outputs of a drainage basin

A
  • the rivers discharge

- water that has been evaporated/transpired and will fall into another drainage basin

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15
Q

What is the watershed

A

The dividing line between neighbouring basins

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16
Q

Three main types of drainage basin

A
  • Those that collect water and deliver directly to the sea
  • Those that are part of much larger drainage basins
  • Those that lead to inland seas or lakes
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17
Q

Characteristics that affect the speed of water flow in a drainage basin

A
  • size
  • shape
  • rock type
  • relief
  • land use
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18
Q

What is the lag time

A

The time it takes for the water to reach the river and cause river levels to rise

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19
Q

What effect does a shorter lag time have on the river

A
  • the quicker the water reaches the basin
  • the more steep the initial rise of water is
  • the greater the risk of flooding
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20
Q

What is the base flow on a storm hydrograph

A

The normal discharge of a river

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21
Q

What is the storm flow on a storm hydrograph

A

The additional discharge of the river as a result of the rainstorm

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22
Q

Biological weathering

A

Rocks are broken apart by vegetation and roots, or chemical reaction from animal faeces erodes the rock face

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23
Q

What are the six factors that affect river regimes

A
  • amount + intensity of rainfall: heavy rain will become surface run off and quickly reach the river
  • temperature: precipitation is snow then will reach river slowly as it has to melt
  • steep slopes: rapid surface run off
  • rock type: impermeable increases surface run off
  • vegetation + land use: trees and plants intercept rain reaching ground whereas bare soil reduces lag time
  • human intervention: dams and reservoirs can hold back water
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24
Q

Acronym for remembering six factors that affect river regimes

A

it’s RVH
I - intensity
T - temperature
S- slopes

R- rock type
V - vegetation
H- human intervention

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25
Q

Define a river regime

A

The seasonal variation in the discharge (volume of water) of a river

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27
Q

Chemical weathering

A

The weak acid in rainwater dissolves chemical compounds in the rocks

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28
Q

Freeze thaw weathering

A

A form of physical sub-aerial weathering where water freezes in the cracks of a rock, expands and enlarges the crack. This weakens the rock overtime leaving it more open to erosion.

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28
Q

Physical weathering

A

Sometimes called mechanical weathering, this is the breakdown of rocks due to forces, not chemical reactions.

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29
Q

What is mass movement

A

Movement of weathered material down a slope by the force of gravity

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30
Q

What is slumping

A

When the side of the valley slope is cut away and the material slumps down towards the river. The water makes the weathered material heavier as well as acting as a lubricant

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31
Q

What is soil creep

A

Weathered material slowly moves down the slope under the influence of gravity and collects at the bottom of the valley and is then eroded by the river

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32
Q

What is hydraulic action

A

When water hits the cliff with such force that material is dislodged and carried away

33
Q

What is abrasion

A

When the material being carried in the river rubs against the floor and sides of the river bed and has a ‘sandpaper’ effect which widens and deepens the river channel

34
Q

What is corrosion (solution)

A

Minerals in the rocks are dissolved by the water flowing past

35
Q

What is attrition

A

When particles become smaller and rounder as they collide with each other however DOES NOT cause river erosion

36
Q

What is the load of a river

A

The movement of material that has been washed or has fallen into the river as well as eroded material

37
Q

What is deposition

A

The laying down of material transported by a river

38
Q

When does deposition happen

A
  • decrease in energy, speed, gradient or discharge
39
Q

What is traction

A

When large boulders are rolled on the river bed

40
Q

What is saltation

A

When small boulders or pebbles are bounced along the river bed

41
Q

What is suspension

A

Lighter material is carried along by river flow

42
Q

What is solution (as a transport method)

A

When material is dissolved and moved in the water

43
Q

Features of the upper course

A
  • source of the river
  • marshy/wet land
  • v shaped valley
  • waterfalls and gorges
44
Q

Characteristics of the upper course

A
  • uplands areas
  • steep slopes
  • rough edges as not much erosion has taken place
45
Q

Features of the middle course

A
  • meanders
  • oxbow lakes
  • river starts to widen
  • settlements on floodplain
  • u shaped valley which begins to widen
46
Q

Characteristics of the middle course

A
  • low land area

- flatter gradient

47
Q

Features of the lower course

A
  • water starts to slow down
  • high levels of deposition
  • deltas and estuaries form
  • river cross profile becomes even wider and deeper
48
Q

Characteristics of the lower course

A
  • ground very low-lying and close to sea level
  • very flat flood plain either side of the river
  • smooth valley sides
49
Q

Which aspects of the Bradshaw model increase as the river flows downstream

A
  • discharge
  • channel width + depth
  • average velocity
  • load quantity
50
Q

Which aspects of the Bradshaw model decrease as the river flows downstream

A
  • load particle SIZE
  • channel bed roughness
  • gradient
51
Q

What are the main upland land forms

A
  • interlocking spurs
  • waterfalls
  • gorges
52
Q

How are main upland features formed

A
  • because of steep GRADIENT of slopes
  • MASS MOVEMENT of material down the sides of the valley
  • some becomes river load and helps the ABRASION process
  • valley floor is NARROW and continues to be CUT DOWNWARDS
53
Q

How are interlocking spurs formed

A
  • river swings from side to side and vertical erosion continues as it moves from alternate sides of the valley
54
Q

How are waterfalls formed

A
  • band of more and less resistant rock
  • the softer rock is easily eroded as if falls overt the hard cap rock
  • falling water gradually creates a plunge pool
  • slowly hard rock is eroded leaving a gorge below it
55
Q

What are the main lowland land forms

A
  • floodplains
  • meanders
  • oxbow lakes
  • deltas
  • leeves by deposition of sediment
56
Q

How are main upland features formed

A
  • VERTICAL EROSION is less intense as altitude drops and becomes closer to sea level
  • lateral erosion is more common as deposition becomes more prevalent
  • river velocity INCREASES as channel is wider, deeper and smoother
57
Q

How are meanders + oxbow lakes formed

A
  • As the river erodes laterally, it forms large bends, and then horseshoe-like loops called meanders.
  • The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
  • The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction. This will form a river cliff.
  • On the inside of the bend, where the river flow is slower, material is deposited, as there is more friction. This will form a slip-off slope.
  • Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through, e.g. during a flood when the river has a higher discharge and more energy, and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.
58
Q

What are deltas

A
  • Vast areas of deposited alluvium at the mouths of rivers
  • load is deposited faster than the tide can remove it, so the river flow is blocked by deposition, so the river splits up into smaller channel known as distributaries
  • These deposit sediment and create new land
59
Q

Available fresh water is used for

A
  • essential to all life
  • vital to economic development
  • unevenly distributed geographically
60
Q

Uses of fresh water

A
  • domestic use: cooking, cleaning, washing
  • industrial use: generating electricity, making clothes/cars
  • agricultural use: irrigation for crops + livestock
  • leisure: - fishing, sailing, watering golf courses
61
Q

What is a country’s water balance

A

Comparison between water demand and water supply

62
Q

Why has water demand increase over the past 50 years

A
  • rising standard of living: better sanitation for washing hands and flushing toilets
  • rising agricultural need for growing population
  • growing industrialisation to generate power and cooling
63
Q

What is water deficit

A

Areas where water balance is negative - the countries demand exceeds its supply

64
Q

What is water surplus

A

Areas where water balance is positive - the countries supply exceeds its demand

65
Q

What does it mean is a country is referred to as water neutral

A

The water supply is roughly the same as its demand

66
Q

Where are the main stores of fresh water

A
  • Rivers and lakes
  • Reservoirs (artificial lakes created by building dams across rivers and flooding them)
  • Aquifers and wells (underground in porous rocks)
67
Q

Main sectors where water pollution occurs

A
  • agriculture
  • industry
  • domestic
68
Q

How does the agricultural industry cause water pollution

A
  • liquid from farm and animals enters rivers
  • fertilizers and pesticides steep into groundwater
  • deforestation: run off carries soil and silt into water harming aquatic life
69
Q

How does the industrial industry cause water pollution

A
  • returning water to source at higher temperature than normal
  • spillages from oil refineries
  • use of metallic minerals in processing ores
70
Q

How does the domestic industry cause water pollution

A
  • discharge of untreated sewage
  • washing clothes or bathing
  • emptying highly chlorinated water from swimming pools
71
Q

What is the five-step process for treating water

A
  • chlorination: to control any biological growth e.g. algae
  • aeration: to remove dissolved iron and manganese
  • sedimentation: to remove suspended solids
  • filtration: to remove very fie sediment
  • disinfection: to remove any bacteria
72
Q

What is the acronym for remembering the five-step process for treating water

A

Charlotte And Sofia Find Doughnuts

73
Q

What is the definition of flooding

A

A flood is when the water in a river exceeds the volume of its channel and overflows its banks, inundating the land on either side of the river (the floodplain).

74
Q

What is flash flooding

A

A flash flood is a very sudden flood, usually the result of very heavy rainfall.

75
Q

What affect does the lag time have on the chance of flooding

A

The shorter the lag time, the greater the chance of flooding

76
Q

What are the 3 main things that cause flooding?

A
  • Impermeable surfaces (due to prolonged dry weather, concrete, rock type or saturated ground)
  • Many tributaries – increases volume of water flowing into the river
  • Deforestation – reduces interception
77
Q

What is hard engineering

A

Management which involves construction using artificial structure such as dams, flood embankments and relief channels
These structures either hold back or help to safely dispose of the flood water. They are generally EXPENSIVE to build

78
Q

What is soft engineering

A

Management is a more natural approach to flood management by working with nature rather than against it
Examples include restoring rivers to its natural state and preserving marshes and wetlands on flood plains to absorb the water (eg parks or football pitches in a city) before houses are built to prevent damage by flooding.

Geography IGCSE (3 decks)

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