The Water Cycle and Water Insecurity EQ1 Flashcards
1
Q
What type of system is the global hydrological cycle?
A
Closed system of linked processes.
2
Q
What is the global hydrological system driven by?
A
Solar energy and gravitational potential energy.
3
Q
Summarise what the global hydrological cycle is.
A
The circulation of water around the earth.
4
Q
Explain what is means that the hydrological cycle is a closed system of linked processes.
A
- There are no external inputs or outputs.
- So the amount of global water is finite and constant.
5
Q
What is the only thing that changes in relation to water in the hydrological cycle?
A
- The state in which the water exists
6
Q
Does the proportions of global water held in each state vary?
A
Yes
7
Q
What does the proportions of global water held in each state vary because of?
A
Over time with changes in climate.
8
Q
How does solar energy drive the hydrological cycle?
A
in the form of heat
9
Q
How does gravitational potential energy drive the hydrological cycle?
A
Causes rivers to flow downhill and precipitation to fall to the ground.
10
Q
What are stores?
A
Reservoirs where water is held.
11
Q
What are the four main stores?
A
- Oceans
- Glaciers and ice sheets
- Surface runoff
- The atmosphere
12
Q
What is the largest store?
A
Oceans
13
Q
What is the second largest store?
A
Glaciers and ice sheets (cryosphere, second largest)
14
Q
What is surface run off an umbrella term for?
A
A number of land-based stores
- including rivers, lakes, groundwater and the moisture held in soils and vegetation.
15
Q
What is the largest fresh water store?
A
The cryosphere is the largest
16
Q
What % of global freshwater is held by the cryosphere?
A
69%
17
Q
What % of global freshwater is held by groundwater?
A
30%
18
Q
What % of freshwater is stored in the biosphere?
A
Less than 1%
19
Q
What are flows?
A
The transfers of water from one store to another.
20
Q
What are flows measured in?
A
km cubed per year.
21
Q
What are the flows in the hydrological cycle?
A
- Oceans and atmosphere
- Atmosphere and landmasses
- Landmasses and oceans
22
Q
Describe the flows in the atmosphere and landmasses (km cubed / year).
A
- Evaporation 60,000
- Precipitation 90,000
23
Q
Describe the flows in the oceans and atmosphere (km cubed / year).
A
- Evaporation 400,000
- Precipitation 370,000
24
Q
Describe the flows in the landmasses and oceans (km cubed / year).
A
- Surface runoff 30,000
25
What are fluxes?
Rates of flow between stores.
26
Where do the greatest fluxes occur?
Over the oceans.
27
What is the global water budget?
Takes into account all the water that is held in stores and flows of the global hydrological cycle.
28
What is the most significant feature of the global water budget?
Only 2.5% of it is freshwater; the rest is in oceans.
29
What % of fresh water is 'easily accessible surface freshwater'?
1%
30
Where is the majority of freshwater locked?
Glaciers and ice sheets.
31
What is a residence time?
The average time a molecule of water will spend in one of the stores
32
Describe the variation of residence times
- From 10 days in the atmosphere
- 3,600 years in the oceans
- 15,000 years in an ice cap.
33
What are the two non-renewable water stores?
Fossil water and the cryosphere.
34
What is fossil water?
Ancient, deep groundwater made from pluvial periods in the geological past.
35
What are pluvial periods?
Wetter
36
What is the cryosphere made up of?
Areas of the world where water is frozen into snow or ice.
37
What % of water is stored in oceans?
97.5%
38
What % of water is freshwater?
2.5%
39
What % of freshwater is stored in ice caps?
69%
40
What % of freshwater is stored in groundwater?
30%
41
What % of freshwater is stored as easily accessible surface water?
1%
42
What % of easily accessible surface water is stored in lakes?
52%
43
What % of easily accessible surface water is stored as soil moisture?
38%
44
What % of easily accessible surface water is stored as atmospheric water vapour?
8%
45
What % of easily accessible surface water is stored in rivers?
1%
46
List What are the flows in the hydrological cycle?
Interception, infiltration, direct runoff, saturated overland flow, throughflow, percolation, groundwater flow
47
What are the outputs of the hydrological cycle?
Evaporation, transpiration and channel flow.
48
What is the main input in the hydrological cycle?
Precipitation
49
How can precipitation vary?
- Form
- Amount
- Intensity
- Seasonality
- Distribution
50
What forms of precipitation are there?
Rain, snow, hail
51
What effect does the form of precipitation have on the drainage cycle?
With snow, entry of water into the drainage system will be delayed.
52
How does the amount of precipitation affect the drainage cycle?
Affects the amount of water in the drainage basin and the fluxes within it.
53
How does the intensity of precipitation effect the drainage cycle?
The greater the intensity, the greater the likelihood of flooding.
54
How does the seasonality of precipitation effect the drainage cycle?
Likely to result in the drainage basin system operating at different flow levels at different times of the year.
55
When does the distribution of precipitation have a more significant impact on the drainage cycle?
In very large drainage basins, such as the Nile and the Ganges, where tributaries start in different climate zones
56
What is interception?
The retention of water by plants and soils which is subsequently evaporated or absorbed by the vegetation.
57
What is infiltration?
The process by which water soaks into, or is absorbed by, the soil.
58
What is percolation?
A deeper transfer of water into permeable rocks.
59
What is throughflow?
The lateral transfer of water downslope through the soil.
60
What is groundwater flow?
The very slow transfer of percolated water through pervious (permeable) or porous rocks.
61
What is surface runoff?
The movement of water that is unconfined by a channel across the surface of the ground.
62
What can surface runoff also be known as?
Overland flow
63
What is river or channel flow?
Takes over as soon as the water enters a river or stream; the flow is confined within a channel.
64
What is evaporation?
The process by which moisture is lost directly into the atmosphere from water surfaces, soil and rock.
65
What is transpiration?
The biological process by which water is lost from plants through minute pores and transferred to the atmosphere.
66
What is discharge (channel flow)?
into another, larger drainage basin, a lake or the sea.
67
What do physical factors within drainage basins determine?
The relative importance of inputs, flows and outputs.
68
What is a drainage basin?
The area of land drained by a river and its tributaries.
69
What is the boundary of a drainage basin defined by?
The watershed
70
What is the drainage basin, within the global hydrological system?
A subsystem.
71
What type of system is the drainage basin?
An open system with external inputs and outputs
72
What does it mean that the inputs within a drainage basin vary overtime?
So does the amount of water in the drainage basin.
73
How do drainage basins vary in size?
From that of a small local stream up to a huge river such as the Amazon.
74
What does climate mainly impact within the drainage basin?
Inputs and outputs
75
What physical factors work within a drainage basin?
Climate, soils, vegetation, geology, relief
76
What else does climate impact within the hydrological system and drainage basin?
- Type and amount of precipitation overall and the amount of evaporation
- vegetation type
77
What do soils largely affect within the drainage basin?
The relative importance of the different flows within the system
(of these flows perhaps the most important is surface runoff)
78
What do soils determine within the drainage basin?
The amount of infiltration and throughflow, and indirectly, the type of vegetation
79
What does geology largely affect within the drainage basin?
- Largely affects the relative importance of the different flows within the system
(of these flows perhaps the most important is surface runoff)
80
What else can geology impact within the drainage basin?
- Subsurface processes such as percolation and groundwater flow (and, therefore, on aquifers)
Indirectly, geology affects soil formation.
81
What does relief largely affect within the drainage basin?
The relative importance of the different flows within the system
(of these flows perhaps the most important is surface runoff)
82
What else does relief impact within the drainage basin?
- The amount of precipitation
- Slopes can affect the amount of runoff
83
What does vegetation largely impact within the drainage basin?
- The relative importance of the different flows within the system
(of these flows perhaps the most important is surface runoff)
84
What else does the presence or absence of vegetation impact within the drainage basin?
- The amount of interception, infiltration and occurrence of overland flow, as well as on transpiration rates.
85
What physical factors largely affects the relative importance of the different flows within the system?
Soils, geology, relief, vegetation
86
What human changes disrupt the drainage basin cycle often by accelerating its processes?
1. rivers and drainage
2. the character of the ground surface (its shape, texture and covering)
87
What factors affect the drainage basin?
- River management
- Deforestation
- Changing land use - urbanisation
- Changing land use - agriculture
88
River management:
- How does construction of storage reservoirs affect the drainage basin cycle?
Holds back river flows
89
River management:
- How does abstraction of water for domestic flow and industrial use affect the drainage basin cycle?
Reduces river flows
90
River management:
- How does abstraction of groundwater for irrigation affect the drainage basin cycle?
Lowers water tables
91
What is a water table?
The boundary between water-saturated ground and unsaturated ground.
92
Deforestation:
How does the clearance of trees affect the drainage basin cycle?
Reduces evapotranspiration, but increases infiltration and surface runoff
93
Changing land use - Agriculture:
How does a shift from arable to pastoral affect the drainage basin cycle?
Compaction of soil by livestock increases overland flow
94
What are arable farms?
Those which produce crops
95
What are pastoral farms?
Those where animals are raised for meat, wool or dairy products.
96
Changing land use - Agriculture:
How does a shift from pastoral to arable affect the drainage basin cycle?
Ploughing increases infiltration by loosening and aerating the soil
97
Changing land use - Urbanisation:
How do urban surfaces affect the drainage basin cycle?
Speed surface runoff by reducing percolation and infiltration
98
Changing land use - Urbanisation:
How do drains affect the drainage basin cycle?
Deliver rainfall more quickly to streams and rivers, increasing chances of flooding.
99
What components of the drainage basin are most affected by humans?
- Evaporation and evapotranspiration
-Interception
- Infiltration
- Groundwater
- Surface runoff
100
What case study can be used to show how deforestation has disrupted the drainage basin?
The Amazonia
101
What does the Amazon basin contain?
The world's largest area of tropical rainforest.
102
How has deforestation disrupted the drainage basin cycle in the Amazon?
Less....
- Less precipitation
103
How has deforestation disrupted the drainage basin cycle in the Amazon?
A lowering of...
- A lowering of humidities
104
How has deforestation disrupted the drainage basin cycle in the Amazon?
More...
- More surface run off and infiltration
- More evaporation, less transpiration
- More soil erosion and silt being fed into rivers.
105
What do the water budgets show?
The annual balance between inputs (precipitation) and outputs (evapotranspiration) and runoff.
their impact on soil water availability
106
What are water budgets influenced by?
Climate type (tropical, temperate or polar examples)
107
What is the formula for the water budget?
P = E + R +/- S
108
What is the water budget at a national or regional scale useful for?
A useful indication of the amount of water that is available for human use
(for agriculture, domestic consumption etc.)
109
What is the water budget at a local scale useful for?
Available soil water.
110
What is available soil water?
The amount of water that can be stored in the soil and is available for growing crops.
111
Why is it valuable for farmers to understand available soil water?
Can use it to identify when irrigation might be required, and how much.
112
What is a river regime?
The annual variation in the discharge or flow of a river at a particular point
113
What is a river regime usually measured in?
cumecs
114
What is the character of a river regime influenced by?
1.
1. the size of the river and where discharge measurements are taken along its course
115
What is the character of a river regime influenced by?
1. the size of the river and where discharge measurements are taken along its course
2.
2. the amount, seasonality and intensity of the precipitation
116
What is the character of a river regime influenced by?
1. the size of the river and where discharge measurements are taken along its course
2. the amount, seasonality and intensity of the precipitation
3.
3. The temperatures, with possible meltwater and high rates of evaporation in the summer
117
What is the character of a river regime influenced by?
1.
2.
3. The temperatures, with possible meltwater and high rates of evaporation in the summer
4.
4. the geology and soils particularly their permeability and porosity;
groundwater noted in permeable rocks is gradually released into the river as base flow
118
What is the character of a river regime influenced by?
1.
2.
3.
4. the geology and soils particularly their permeability and porosity;
groundwater noted in permeable rocks is gradually released into the river as base flow
5.
5. The type of vegetation cover: wetlands can hold water and release it slowly into the river
119
What is the character of a river regime influenced by?
1.
2.
3.
4.
5. The type of vegetation cover: wetlands can hold water and release it slowly into the river
6. Human activities aimed at regulating a river's discharge
120
What do storm hydrographs show?
discharge changes over a short period of time, often no more than a few days.
121
What do storm hydrographs' shape depend on?
Physical features of drainage basins as well as human factors
122
What are physical features of a drainage basin?
Size, shape, drainage density, rock type, soil, relief and vegetation
123
What human factors affect drainage basins?
Land use and vegetation
124
What two things do storm hydrographs plot?
The occurrence of a short period of rain over a drainage basin
And the subsequent discharge of a river.
125
What is the variation in the shape of storm hydrographs linked to?
The nature of the rainfall event.
126
What are the main features of a storm hydrograph?
- Rising limb
- Peak discharge
- Lag time
- Falling / recessional limb
- Base flow
127
What is a rising limb?
Once the rainfall starts, the discharge begins to rise
128
When is peak discharge reached?
Some time after the peak rainfall
129
Why is peak discharge reached some time after the peak rainfall?
Because the water takes time to move over and through the ground to reach the river.
130
What is lag time?
The time interval between peak rainfall and peak discharge
131
What does the recessional or falling limb show?
Once the input of rainwater into the river starts to decrease, so does the discharge
132
What is base flow?
The river's discharge returns to its normal level
133
Urbanisation and the hydrological cycle:
How does construction work impact surface runoff?
- Construction work leads to the removal of the vegetation cover. This exposes the soil and increases vegetation cover
- Bare soil is eventually replaced by a covering of concrete and tarmac, both of which are impermeable and increase surface runoff
134
Urbanisation and the hydrological cycle:
What is the impact of high density buildings ?
- Rain falls on roofs and is then swiftly fed into drains by gutters and pipes.
- Drains and sewers reduce the distance and time rainwater travels before reaching a stream or river channel.
135
Urbanisation and the hydrological cycle:
How do drains and sewers impact rainwater travel?
Reduce the distance and time rainwater travels before reaching a stream or river channel.
136
Urbanisation and the hydrological cycle:
How do urban rivers impact flooding?
Urban rivers are often channelised with embankments to guard against flooding. When floods occur, they can be more devastating.
137
Urbanisation and the hydrological cycle:
How do bridges impact floods?
Bridges can restrain the discharge of floodwaters and act as local dams, thus prompting upstream floods.
