Water And Carbon Flashcards
What does the availability and quantity of water help tie together
The Earths lands, oceans and atmosphere into an integrated physical system
What is the most important greenhouse gas
Water vapour
What does the poor understanding of the water cycles interactions and processes at a variety of scale lead to
Bad representation in model predications
Where is carbon stored
Everywhere: in the oceans, rocks and soil, in all forms of life and our atmosphere
What does the well-bring and functioning of our planet depend on
Carbon and how it cycles through the Earths system
How does the carbon cycle play a key role in regulating the global temperature and climate change
By controlling the amount of another greenhouse gas, carbon dioxide, in the atmosphere
What is a flow/transfer
A form of linkage between one store/component and another that involved movement of energy or mass
What is an input
The addition of matter and/or energy into a system
What is a store/ component
A part of the system where energy/ mass is stored or transformed
What is a system
A set of interrelated components working towards some kind of process
Why do geographers attempt to simplify aspects of the Earth
It is highly complex.
They want relationships between components to be better understood.
What are simplifications of highly complex processes called
Models such as the water cycle or the demographic transition model
What is a type of model that is widely used
The system
What are the three properties of systems
Elements
Attributes
Relationships
What are elements in the system
The things that make up the system
What are attributes of a system
The perceived characteristics of the elements
What are the relationships in a system
Descriptions of how the various elements (and their attributes) work together to carry out some kind of process
What are the four common characteristics of systems
- structure that lies within in a boundary.
- generalisations of reality, removing incidental detail that obscures fundamental relationships.
- they function by having inputs and outputs of material that is processes within the components causing it to change.
- involve the flow of material between components.
What are the three classifications of systems
Isolated systems
Closed systems
Open systems
What are isolated systems
They have no interaction with anything outside the system boundary. No inputs or outputs of energy. Many controlled lab experiments are this type of systems but they are rare in nature.
What is a closed system
Transfers of energy both into and beyond the system boundary but not transfer of matter
What are open systems
Matter and energy transferred from the system across the boundary into the surrounding environment. Most ecosystems are an example of this.
Specific example of an open system
A drainage basin hydrological system
When is a system said to be in a state of dynamic equilibrium
Where there is a balance between the inputs and outputs
What is feedback
When one of the inputs increases without any corresponding change in the outputs - the stores changes
What are the two types of feedback
Positive feedback
Negative feedback
What is positive feedback
Where the effects of an action are amplified or multiplied by subsequent knock-on or secondary effects (for example increase in carbon dioxide)
What is negative feedback
Where the effects of an action are nullified by subsequent knock-on effects (for example the increased use of fossil fuels)
Example of positive feedback in the carbon cycle system
More Co2 in the atmosphere. (This acts as a greenhouse gas) Global temperature rise. (This warms the ocean) Increased oceanic temperatures. (Warm water less able to dissolve gas) Dissolved Co2 release by warmer oceans. (Co2 back into the atmosphere) More Co2 in the atmosphere.
Example of negative feedback in the carbon cycle
Increased use of fossil fuels. Increased in atmospheric Co2. Global temperature increase. More plant growth. Increased take up of Co2. Reduces atmospheric Co2. This has dampening effect and reduce global temperature.
How does energy come into the system
Form of solar energy
What is the energy coming into systems in the form of solar energy balanced by
Radiant energy lost by the Earth
What is ‘Spaceship Earth’
A term to express the concern over the use of limited resources available on Earth and encouraging everyone on it to act as a harmonious crew working towards the greater good
What are the four major subsystems at a global level on the Earth
Atmosphere
Lithosphere
Hydrosphere
Biosphere
What is a cascading system
An open system that forms part of a chain such as the four major subsystems on Earth
What has a profound effect on the Earths climate and climate change
Interlocking relationships amount the atmosphere, lithosphere, hydrosphere and biosphere
What is vital to life on Earth
The availability and quantity of water
What is the global water cycle driven by
Many complex processes and interactions at a variety of scales
What is atmospheric water
Water found in the atmosphere; mainly water vapour with some liquid water (cloud and rain droplets) and ice crystals
What is cryospheric water
The water locked up in the Earths surface as ice
What is the hydrosphere
A discontinuous layer of water at or near the Earths surface. It includes all liquid and frozen surface waters, groundwater held in soil and rock and atmospheric water vapour
What is oceanic water
The water contained in the Earths oceans and seas but not including such inland seas as the Caspian Sea
What is terrestrial water
This consists of groundwater, soil moisture, lakes, wetlands and rivers
Who said ‘Water is life’s matter, mother and medium’
Albert Szent-Gyorgyi, 1937 Nobel Prize acceptance speech
Percentage of all water on earth
97% ocean
3% fresh water
What are the percentages of stores in fresh water
Ice caps and glaciers 79%
Groundwater 20%
Easily accessible surface fresh water 1%
What are the percentage of stores in easily accessible surface fresh water
Lakes 52% Soil moisture 38% Atmospheric water vapour 8% Rivers 1% Water within living organisms 1%
Important percentages to know for all water on plent earth
3% is fresh water
Of this, 1% is easily accessible
Of this, 52% is lakes, 38% is soil moisture
What is the general agreement that scientists have come to on the amount of water in the hydrosphere
Estimated at 1.338 x 10^9 km^3
Examples of cryospheric water
Sea Ice Ice caps Ice sheets Alpine Glaciers Permafrost
Examples of terrestrial water
Groundwater Lakes Soil Wetland Rivers Biomass
How much water vapour is found in the atmosphere
12,900km^3 which is a global average of 26kg/m^2 for each column of air on the surface of the earth
What percentage of water on earth is atmospheric water
0.4% and is has a profound effect on our lives at present
What is the amount of water in the stores in a state of
Dynamic equilibrium with changes at a range of timescales from diurnal to geological
In the future, what could changes in the amount of atmospheric water cause
Important effects on climate change
What do the figure of the amount of water in the ocean range from
1,320,000,000 to 1,370,000,000km^3 with an average depth of 3,682m.
What percentage of the planets surface does oceanic water cover
72%
What is oceanic water customarily divided into
Several principal oceans and smaller seas
While the ocean contains 97% of the worlds water, how much have oceanographers stated have been explored
5%
Why does oceanic water taste salty
Because it contains dissolved salts
What do the salts in oceanic water allow
It to stay as liquid water even below 0*C
What is the pH of oceanic water
Alkaline with an average pH of about 8.14
What has the pH fallen from in the last 250 years
Fallen from 8.25 to 8.14 and is destined to continue falling
What is the change in the pH of oceanic water linked to
The increase in atmospheric carbon
What may the change in pH have an influence on
Marine ecosystems
Example of sea ice
The Ross Ice Shelf
Example of an ice cap
The Iceland Ice Cap
Example of an ice sheet
The Greenland ice sheet
Example of alpine glacier
Mer de Glacé, France
Example of permafrost
The Alaska North Slope
Why does the amount of water frozen In Arctic Ocean change
It grows in winter and shrinks in summer, same is true for the waters in Antarctica
What is much of the Arctic Ocean
Frozen
When does sea ice form
When water in the oceans is cooled to temperatures below freezing
Why does sea ice not raise sea levels when it melts
Because it forms from the ocean waters
Why are scientists concerned about the recent decline of sea ice
It is closely linked with our planets climate
What are ice shelves
Platforms of ice that form where ice sheets and glaciers move out into the oceans
Where do Ice shelves mainly exist
In Antarctica and Greenland, as well as in the Arctic near Canada and Alaska
What are icebergs
Chunks of ice that break off glaciers and ice shelves and drift in the ocean
When do Ice burgs raise sea levels
When they first leave land and push into the water, but not when they melt in the water
What is an ice sheet
A mass of glacial land ice extending more than 50,000km^2
What do the two major ice sheets on Earth today cover
Most of Greenland and Antarctica
During the last advance, where did ice sheets cover
North America
Northern Europe
Argentina
Along with Greenland and Antarctica
Together, how much of freshwater on earth is contained in the Antarctica and Greenland ice sheets
99%
How far does the Antarctic Ice sheet extend
14 million km^2 - roughly the area of the United States and Mexico combined
How much ice does the Antarctica ice sheet contain
30 million km^3
How far does the Greenland Ice sheet extend
About 1.7 million km^2, covering most of the island of Greenland
Where do Ice sheets form
In seas where snow that falls in the winter does not melt entirely over the summer
How do ice sheets form
Over thousands of years, the layers of snow pile up into thick masses of ice, growing thicker and denser as the weight of new snow and ice layers compresses the older layers
How are Ice sheets constantly in motion
They are slowly flowing downhill under their own weight
Near the coast, how do most ice sheets nice
Through relatively fast-moving outlets called ice streams
Where are Ice sheets significant and why
In the Antarctic
How big can Ice sheets get in the Antarctic
50km wide
2km thick
Hundreds of kilometres King
What conditions are needed for an ice sheet to remain stable
As long as an ice sheet accumulated the same mass of snow as it loses to the sea
If the Greenland ice sheet melted, what do scientists estimate that sea levels would rise by
6m
If the Antarctic Ice sheet melted, what do scientists predict the rise in sea level would be
About 60m
What are ice caps
Hick layers of ice on land that are smaller than 50,000km^2
Where are ice caps usually found
Mountainous areas, They are usually centred over the highest point of an upland area
What shape are ice caps
Dome-shaped
How do ice caps flow
Outwards, covering almost everything in their path becoming a major source for glaciers
Where do ice caps occur in the world
All over - from the polar regions to mountainous ones such as the Himilayas, the Andes and the Southern Alps of New Zealand
What is Africa’s only remaining ice cap
The Furtwangler Glacier In Kilimanjaro at 60,000m^2. It is melting rapidly and any soon disappear
What are Alpine glaciers
Thick masses of ice
Where are alpine glaciers found
In deep valleys or upland hollows
What are most valley glaciers fed by
Ice from ice caps or smaller corrie glaciers
Why are alpine flavoured important in the Himalayas
15,000 Himalayan glaciers form a unique reservoir which supports perennial rivers which are the lifeline of millions of people in south Asian countries
What are perennial rivers in the Himalayas
Indus
Ganges
Brahmaputra
Examples of South Asian countries
Pakistan Nepal Bhutan India Bangladesh
What ring the Arctic Ocean
Frozen ground and permafrost while glaciers , snow and ice cover the nearby land including Greenland
What is permafrost
Ground (soil or rock and included ice or organic material) that remains at or below 0*C for at least two consecutive years
What does the thickness of permafrost vary between
Less than 1 metre to more than 1,500m
When did most of the permafrost existing today form
During cold glacial periods and has persisted through warmer interglacial periods, including the Holocene.
What is the Holocene
The last 10,000 years
When did some relatively shallow permafrost (30 to 70m) forms
During the second part of the Holocene (last 6,000 years) and some during the Little Ice Age (from 400 to 150 years ago)
When was the Little Ice Age
From 400 to 150 years ago
When does Subsea permafrost occur
At close to 0*C over large areas of the Arctic continental shelf, where it formed during the last glacial period on the exposed shelf landscapes when sea levels were lower
Where is permafrost found
Beneath the ice-free regions of the Antarctica continent and also beneath areas in which the ice sheet is frozen to its bed
Why has permafrost begun to melt
As climate warms
How does melting permafrost affect global climates
Because it releases large amounts of carbon dioxide and methane
What are the four broad classes terrestrial water falls into
Surface water
Groundwater
Soil water
Biological water
What is surface water
The free-flowing water of rivers as well as the water of ponds and lakes
What do rivers act as
Both a store and a transfer of water
How are rivers a store and a transfer of water
Streams of water within a defined channel.
Transfer water from the ground, from soils and from the atmosphere to a store
What may the store that rivers transfer water to be
Wetlands
Lakes
Oceans
What percentage of all rivers do rivers make up
0.0002%
What is the overall volume and span of all rivers
1,000,000km^3 span and 2,120km^3 volume
Which River is the largest river by discharge of water in the world
The Amazon in South America
What is the discharge of the Amazon river
209,000m3/s, greater than the next seven largest independent rivers combined
What area approximately does the Amazon river drain
7,050,000km^3
How much of the worlds total river flow does the Amazon account for
One fifth
How big is the Amazon drainage basin in Brazil
The portion of the rivers drainage basin in Brazil alone is larger than any other rivers basin
How much of the Amazons final discharge into the Atlantic Ocean enters Brazil
Only one fifth, yet it has already a greater flow than the discharge of any other river
What are mailed
Collections of fresh water
Where are lakes found
In hollows in the land surface
How big are lakes
Greater than 2 hectare season in area
What is a standing body of water smaller than 2 hectares termed
A pond
What are the majority of lakes on earth
Freshwater
Where do most lakes on earth lie
In the Northern Hemisphere at high altitudes
How many lakes that are larger than 3km^2 does Canada have
31,752
How many lakes does Canada have overall
Estimated total of at least 2 million
How many lakes does Finland have
187,888 that are 500km^2 or larger, of which 56,000 are large (10,000m^2)
What is the largest lake and how big is it
The Caspian Sea at 78,200km^3
How old is the Caspian Sea
As it is a remnant of an ancient ocean it is about 5.5 million years old
What is the Caspian Sea generally
Fresh water though it becomes more saline in the south where there are few rivers flowing into it
What is the deepest lake in the world
Lake Baikal in Siberia with a mean depth of 749m and a deepest point at 1,637n
What are does the Ramsar Convention define Wetlands
The Ramsar Convention defines them as ‘areas of marsh, fen, peatland or water whether natural or artificial, permanent or temporary, with water that is static or flowing where there is a dominance by vegetation’
Simple definition of wetlands
Areas where water covers the soil, or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season
What does water saturation determine
How the soil develops and the types of plant and animal communities living in and on the soil
What species may wetlands support
Both aquatic and terrestrial
What does the prolonged presence of water in wetlands create
Conditions that favour the growth of specially adapted plants and promotes the development of characteristic wetlands soils
What are the 7 reasons wetlands vary widely
Because of regional and local differences in soils. Topography. Climate. Hydrology. Water chemistry. Vegetation. Other factors like human disturbance.
Where are wetlands found
From the polar regions to the tropics and on every continent except Antarctica
Example of a wetland
The Pantanal of South America, often referred to as the worlds largest freshwater wetlands systems
How far does the Pantanal of South America extend
Through millions of hectares of central western Brazil, eastern Bolivia and eastern Paraguay
What is the Pantanal of South America
A complex system of marshlands, flood plains, lagoons and interconnected drainage lines
How does the Pantanal of South America provide economic benefits
It is a huge area for water purification and groundwater discharge and recharge, climate stabilisation, water supply, flood abatement and an extensive transport system
What are the main ecosystems in the Arctic
Wetlands
What covers nearly 60% of the Arctic
Peatland, rivers, lakes and shallow bays
What do Arctic wetlands store
Enormous amounts of greenhouse gases
What are Arctic wetlands critical for
Global biodiversity
What is groundwater
Water that collects underground in the lite spaces of rock
What have scientists said is the depth of groundwater
4,000m but it is known there are large quantities of water blow that
What was found in Northern Russia
A very deep borehole in the Kola Peninsula, found huge quantities of hot mineralised water at a depth of 13km
What is the water table
The depth at which soil purr spaces of fractures and voids in rocks become completely saturated with water
What eventually happens to groundwater
It is recharged from and eventually flows to the surface.
Sometimes natural discharge can occur at springs and seeks and can form oases or wetlands.
Why is the amount of groundwater reducing rapidly
Due to extensive extraction for use in irrigating agricultural land in dry area
What is soil water
That which is held together with air in unsaturated upper weathered layers of the earth
What is soil water of fundamental importance to
Many hydrological, biological and biogeochemical processes
What 6 things does soil water affect
Weather and climate. Run-off potential and flood control. Soil erosion and slope failure. Reservoir management. Geotechnical engineering. Water quality.
What is soil moisture a key variable in
Controlling the exchange of water and heat energy between the land surface and the atmosphere through evaporation and plant transpiration
What does soil moisture play an important role in
The development of weather patterns and the production of precipitation
What is biological water
Constitutes the water stored in all the biomass
What does biological water around the globe depend on
He vegetation cover and type
Where stores more biological water than a desert
Areas of dense rainforest
What is the role of animals as a water store
Minimal
How do trees take in water
Via their roots
How is water transported in trees
Transported or stored in the trunk and branches of the tree
How is water lost in trees
By the process of transpiration through stomata in the leaves
What does the storage of water in trees provide
A reservoir of water that helps maintain some climatic environments
If the vegetation is destroyed, what happens to the biological water
The store is lost to the atmosphere and he climate can become more desert-like
How much water are many plants adapted to store
Large quantities
How do Cacti gather water
Via their extensive root system and then very slowly use it until the next rainstorm
Why does the baobab tree store water
To strengthen the structure of the tree rather than to be used in tree growth
What states does atmospheric water exist in
All three states
What is the most common atmospheric water
Gas; water vapour
What is water vapour
A clear, colourless and odourless gas
Why is atmospheric water important
It absorbs, reflects and scatters incoming solar radiation, keeping the atmosphere at a temperature that can maintain life
What does the amount of water vapour that can be held by the air depebd in
It’s temperature
Why is the air in the poles quite dry, whereas air in the tropics is very humid
Because cold air cannot hold as much water vapour as warm air
What will a small increase in water vapour lead to
An increase in atmospheric temperatures
How does an increase in water vapour in the atmosphere become positive feedback
A small increase in global temperatures would lead to a rise in global water vapour levels, thus further enhancing the atmospheric warming
What is a cloud
A visible mass of water droplets or ice crystals suspended in the atmosphere
What is cloud formation the result of
Air in the lower layers of the earths atmosphere becoming saturated due to either or big of two processes: cooling of the air and an increase in water vapour
What happens when cloud droplets grow
They can eventually fall as rain
What are the 3 factors driving the change in magnitude of water stores
Evaporation
Condensation
Cryopheric processes
What is it called when water vapour is turned to liquid
Condensation, releasing latent heat of vaporisation
What’s the process of liquid to solid
Freezing, releasing latent heat of fusion
What’s the process of ice to water
Sublimation, absorbing latent heat of sublimation
What’s the process of gas to solid
Deposition, releasing latent heat of sublimation
What’s the process of ice to liquid
Melting, absorbing latent heat of fusion
What’s the process of water to gas
Evaporation, absorbing latent heat of vaporisation
What happens to energy, in the form of latent heat, in the phases of water and the phase changes
It is either absorbed or released depending on the process
Where is energy in the form of latent heat particularly important
In atmospheric processes such as cloud or precipitation formation
When does evaporation occur
When energy from solar radiation hits the surface of water or land and causes liquid water to change state from a liquid to a gas
What 4 factors does the rate of evaporation depend on
Amount of solar energy.
Availability of water (e.g more evaporation than a pond then a grassy field).
Humidity of the air (closer the air is to saturation point, the slower the rate of evaporation).
Temperature of the air (warmer air can hold more water than cold air).
What do all terrestrial plants lose water through
Transpiration
What is transpiration
Water is transported from the roots of a plant to its leaves and then lost through pores on the lead surfaces
What can water trapped on leaves be
Evaporated before t reaches the soil
When water evaporates why does it cool its surroundings
It uses energy in the form of latent heat
Explain the process of condensation
As air cools it is able to hold less water vapour.
This means that if it is cooled sufficiently then it will get to a temperature at which it becomes saturated.
This is known as the dew point temperature.
Excess water in the air will then be converted to liquid water in the process of condensation.
What do water molecules need in the process of condensation
Something to condense on
What can water molecules condenser on
Tiny particles like smoke, salt, dust etc that are collectively called condensation nuclei or surfaces like leaves, grass stems and windows that are blow the dew point temperature
What does sublimates mean
Changing directly from gas to solid in the form of hoar frost, done when the surface the vapour is condensing in is below freezing point
What is condensation the direct form of
All forms of precipitation
When does condensation take place
When the temperature of air is reduced to dew point but it’s volume remains constant.
When the volume of air increases but there is no addition of heat.
What is adiabatic cooling
During condensation, when the volume of air increases but there is no addition of heat
When does adiabatic cooling occur
When air rises and expands in the lower pressure of the upper atmosphere
When does the temperature of the air reduce to dew point while the volume remains constant
Warm moist air passes over a cold surface.
On a clear winters night heat is radiated out to space and the ground gets colder, cooling the air directly in contact with it.
When 3 effects cause adiabatic cooling to occur
Relief or orographic effect.
Frontal effect.
Convectional effect.
What is relief or orographic effect
Air is forced to rise over hills
What is the frontal effect
Masses of air of different temperatures and densities meet. The less dense warm air rises over the denser cold air
When does the convectional effect occur
When localised warm surfaces heat the air above, this expands and become less dense and rises
What are the two cryospheric processes
Accumulation
Ablation (melting)
What is there thought to have been in Earths history
5 major glacial periods
When did the most recent glacial period start
2.58 million years ago and continues today
What is the most recent glacial period called
The Quaternary glaciation
During the Quaternary period what was there
Glacial periods when , due to the volume of ice on land, sea level was approx 120m lower than present and continental glaciers covered large parts of Europe and North America. This represents an interruption in the global hydrological cycle.
Interglacial periods when global ablation exceeds accumulation and the hydrological cycle as we know it today returns.
Over the past 740,000 years how many glacial cycles has there been
8
When is permafrost formed
When air temperatures are so low that they freeze any soil and groundwater present.
Why does permafrost rarely occur under ice
Because the temperatures are not low enough
What is the driving force behind global cloud formation and precipitation
The global atmospheric circulation model
Global atmospheric circulation model summary
At the equator high temperatures result in high rates of evaporation. The warm, moist air rises, cools and condensers to form towering banks of cloud and heavy rainfall in a low pressure zone called the ITCZ:
In the mid latitudes, cloud formation is driven by the convergence of warm air from the tropics and cold air from the Arctic. The boundary of these two distinct air masses - the polar front - results in rising air and cloud (and rain) formation. Strong upper-level winds (the jet stream) drive here unstable weather systems across mid latitudes, establishing the largely changeable conditions experienced in the Uk.
Cloud formation can occur on a more localised scale. The formation of thunderstorms from intense convection activity is somewhat ‘hit and miss’, but it does clearly demonstrate the variations in both time and space of water cycle transfer processes.
On a glacier what does the equilibrium line mark
The altitude where annual accumulation and melting are equal
What is the ITCZ
Inter-Tropical Convergence Zone
What could the total melting of all the polar sheets result in
A 60m rise in sea level
How are rising sea levels a positive feedback in the rate of removal of glacial ice
They can destabilise glaciers and ice shelves leading to accelerated rates of iceberg calving
What are cryospheric processes
Processes that affect the total mass of ice at any scale from local patches of frozen ground to global ice amounts. This includes accumulation (build up of ice mass) and ablation (the loss of ice mass)
What is a drainage basin
The area of land drained by a river and its tributaries. It includes water found in the surface, in the soil and in near-surface geology
What is energy provided by and aided by to cause evaporation
Provided by the sun and aided by the wind
What is evapotranspiration
The total output of water from the drainage basin directly back into the atmosphere
What is groundwater flow
The slow movement of water through underlying rocks
What is infiltration
The downward movement of water from the surface into soil
What is interception storage
The precipitation that falls on the vegetation surfaces of human-made cover and is temporarily stored in these surfaces. Intercepted water can either be evaporated directly to the atmosphere, absorbed by the canopy surfaces or ultimately transmitted to the ground surface
What is overland flow
The tendency of water to flow horizontally across land surfaces when rainfall has exceeded the infiltration capacity of the soil and all surfaces stored are full to overflowing
What is percolation
The downward movement of water within the rock under the soil surface. Rates vary depending on the nature of the rock
What is run-off
All the water that enters a river channel and eventually flows out of the drainage basin
What is saturated
This applies to any water store that has reached its maximum capacity
What is the stem flow
The portion of precipitation intercepted by the canopy that reaches the ground by flowing down stems, stalks or tree bole
What is a storm event
An individual storm is defined as a rainfall period seperated by dry intervals of at least 24 hours (Hamilton)
What is a rainfall event
Defined as a rain fall period separated by dry intervals of at least 4 hours (Hamilton)
What is throughfall
The portion of the precipitation that reaches the ground directly through gaps in the vegetation canopy and drips from leaves, twigs and stems
When does throughfall occu
When the canopy-surface rainwater storage exceeds its storage capacity
What is throughflow
The movement of water down-slope through the subsoil under the influence of gravity.
When is throughflow particularly effective
When underlying permeable rock prevents further downward movement
What is transpiration
The loss of water from vegetation through pores (stomata) on their surfaces
What is the water balance
Balance between inputs (precipitation) and outputs (run off, evapotranspiration, soil and groundwater storage) in a drainage basin
What is a useful way of looking at drainage basins
Consider them as cascading systems - they are a series of open systems hat link together so that the output of one is the input of the next
What supplies a river with it’s supply of water
A drainage basin
What are drainage basins seperated from one another by
High land called a watershed
What is the input to a drainage basin
Precipitation
What has a direct bearing on what happens when the water hits the ground
The nature, intensity and longevity of the precipitation
On a hill slope what happens to precipitation
It lands on the bare surface or more likely vegetation cover.
The vegetation provides an interception store.
What does the density of vegetation mean
That interception store is more
What have studies shown of forests made up of needle-leaf trees
They capture 22% of rainfall
What have studies shown about broad-lead deciduous forests
They intercept 19% of rainfall
What is the difference in rainfall capture between needle-leaf trees and deciduous tree because rid
Density of the vegetation cover rather than the structure of the leaves
What do some tropical rainforests intercept
As much as 58% of the rainfall
What happens to a lot of the water captured by vegetation surfaces
It is evaporated back into the atmosphere
What is the infiltration rate
The rate of infiltration
What is the movement of water into soil controlled by
Gravity
Capillary action
Soil porosity (most important)
What is a soils porosity controlled by
It’s texture, structure and organic content
What do coarse textured soils have
Larger spores and fissures than fine grained soil and allow for more water flow
What can pores and fissures in soil be made larger through
A number of factors that enhance internal soil structure. For example, the burrowing of worms and penetration of plant roots csn increase the size and number of macro and micro-channels within the soil
When does the rate of infiltration normally decline rapidly
During the early part of a rainstorm event
When does infiltration rates reach a constant value
During a rainstorm event after several hours of rainfall
What are 3 reasons for the phenomenon of infiltration dates declining rapidly and then reaching a constant value during a rainstorm event
Filling of pores on the soil surface reduces the ability of capillary forces to actively move water into the soil.
As soil moistens, clay particles absorb water causing them to expand. This expansion reduces the size of soil pores.
Raindrop impact breaks larger soil clumps into smaller particles, these then clog soil surface pores reducing movement of water into soil.
What is soil storage
The amount of water stored in the soil
What does soil consist of
Solid particles with pore spaces between them
What can soil pore spaces be filled with
Air as well as water
How much do the pores in a clay soil account for of the total volume
40 to 60 %
How much do the pores in fine sand account for of the total volume
20 to 45%
What is vegetation storage
Plans removing water from the soil and storing it in the structure of the plant
What happens if rainfall institutions is greater than the infiltration rate
The soil will have reached infiltration capacity and the soil will be saturated
What is surface storage
Water building up on the surface usually in the form of puddles
Where is surface storage common
In man-made environments
What is the infiltration rate usually greater than in natural environments
Greater than the rate of precipitation
When does water build up on the surface
After a long period of rain
An intense rainstorm
Impermeable surface such as an impacted foot path or a frozen surface
Why is the total amount of evaporated water referred to evapotranspiration
Because it is difficult to separate evaporation from transpiration so the total amount outputted is called this
When does overland flow/ sheet flow occur
When the surface stores are full then these will occur on slopes
How fast is overland flow
Very fast flow, rapidly reaching the newest channel
What tends to be much slower than overland flow
Throughflow
What happens to throughflow in a very vegetated area
It has a faster rate becsuse it is aided by root channels in the soil
What is the vertical transfer that happens after infiltration
Percolation which can then be held in pore spaces in the rocks as groundwater
What is groundwater flow
Groundwater passing slowly into the zone of saturated rock where it can then more vertically and laterally by this process, very slow movement
What can groundwater flow feed
Rivers through long periods of drought
What is an aquifer
Rocks that are able to store a lot of water, especially if they are porous
What do the sum of all the movements and stores of water add up to form
The drainage basin hydrological cycle
How do rivers transfer water
By channel flow
What is the amount of water that leaves the drainage basin through channel flow called
Run-off
What is the fastest movement of water and why
Along the surface becsuse there are relatively few obstacles slowing it down
Why do urban surfaces have especially fast water movement
Because they are often designed to move the water quickly by having strategically placed slopes and very smooth surfaces
What are the differences of throughflow in woodlands compared to clay soil
Under woodlands there are many channels created by roots as well as burrowing animals and these allow relatively free movement. Whereas clay soils retain water, hindering ant movement, they can dry out from the surface down before they allow any horizontal movement.
How long can groundwater be held and why
A millennia because once the waters in the docks the rate of transfer slows considerably
What are the varying timescales of water movements
LOOK AT SFUDENT NOTES
What is the net transport from ocean to land with about the same amount returning by the rivers to the ocean
38 units
What indicated a considerable recirculating of water over land
The amount of precipitation over the continents is almost three times as high than that over oceans
What does the recirculation of water over land have
A marked annual cycle as well as having large variations between continents
When is the recirculation of water over land larger
During the summer and for tropical land areas
Where does most of the water from the Pacific Ocean recirculate between
Different parts of the Pacific itself with there being little net transport towards land
The pattern of water exchange between ocean and land is different in which oceans
The Atlantic and Indian Ocean
What fraction of the total net transport of water towards continents come from the Atlantic Ocean
2/3s
Where does 2/3s of the total net transport of water towards continents come from
The Atlantic Ocean with the rest essentially from the Indian Ocean
Where does most of the continental water for North and South America, Europe and Africa emanates from and is returned to
From the Atlantic Ocean and returned to there by rivers
What is known as the water balance/budget
Within a drainage basin, the balance between inputs and outputs is known as this
When do rivers occur
Only if the stores are able to release water, there is a direct precipitation, or there is overland flow into the river
As a river moves downstream, what are they fed by
Their tributary streams
What is the rivers regime
Discharge levels rise and fall often showing an annual pattern - a rivers regime
What can the water balance be calculated by
Precipitation (P) = Discharge (Q) + Evapotranspiration (E)
+/- changes in storage (S)
What are the two most important parts of the water balance
Precipitation and ‘potential’ evapotranspiration
What is evapotranspiration closely related to
The prevailing temperature, the warmer it is the higher the evapotranspiration. It is often the case that the temperature, and so the atmospheres ability to hold water vapour, is greater rhan the amount of water available
What is potential evapotranspiration
The amount of water that could be evaporated or transpired (or both) from an area if there was sufficient water available
What is the relationship between precipitation and potential evapotranspiration for a place over a year illustrated by
A soil moisture graph
What does a soil moisture graph look like for eastern England
During Half of October, November, December, January and half of February: precipitation is higher than potential evapotranspiration and so the soil water store is fully recharged.
During other half of Febuary, March and April: precipitation is greater than PET so all space in the soil has been filled so it is in surplus, groundwater recharged and overland flow can occur leading to flooding.
During May, June, July: as it warms up PET exceeds precipitation so the water store is being used by plants (utilisation)
During August, September and the first half of October: there is a deficit of soil water. Plants either wilt or have adaptions fo survive dry conditions as the PET is falling rapidly.
PET rises to a peak in July and falls down again.
Precipitation gets only a little less during the peak of PET.
Why do soil moisture graphs vary significantly
It depends on the climate
What does a soil moisture graph look like for an equatorial area
The rainfall has two marked maxima. Because the temperatures vary very little throughout the year the PET stays relatively constant. High rain fall fills the soil stores rapidly. In short time between the rainfall maxima, soil water does not go into deficit and so rivers and plants have a source of water all year round. High potential of flooding between Februrary and June and again in August to November.
Example of Equatorial area
Yaounde, Cameroon
Soil moisture graph for a tropical wet/dry climate
During the rainy season (July to October) the soils are recharged until there is a surplus. This does not last long when rain stops. There is a short period of utilisation but from December to July the soil is dry. River levels fall with many drying up all together.
Example of a tropical wet/dry climate
Navrongo, Northern Ghana
How have vegetation adapted to fit sigh the tropical climate soil moisture graphs
Vegetation has adapted to this seasonal water supply by evolving characteristics to enable it to survive drought.
How have humans adapted to fit with tropical climates soil moisture graphs
By following migrating herds of animals that have themselves migrated flowing the rains north and south
How is river flow studied
By measuring the discharge of a river
How do you calculate river discharge
Multiplying the cross-sectional area of the river by its velocity at the measuring point
What is river discharge measured by
M^3/secs or cumecs
What does bankfull mean
The maximum discharge that a river channel is capable of carrying without flooding
What is the base flow
This represents the normal day-to-day discharge of the river and is the consequence of slow moving soil throughflow and groundwater seeping into the river channel
What is the discharge of a river
The amount of water in a river flowing last at a particular point
What is the lag time
The time between the peak rainfall and peak discharge
What is the peak discharge
The point on a flood hydrograph when river discharge is at its greatest
What is a storm flow
Discharge resulting from storm precipitation involving both overland flow, throughflow and groundwater flow
What is a storm hydrograph
A graph of discharge of s river over the time period when the normal flow of a river is affected by a storm event
What is discharge the combined result of
The many climatological and geographical factors which interact within a drainage basin
What is the knowledge of discharge very important in
The assessment and management of water resources (including irrigation provision), the design of water related structures (reservoirs, bridges, flood banks, urban drainage schemes’ sewage treatment works) and flood warning and alleviation schemes.
It can also help in developing hydroelectric power and protecting both the ecological health of watercourse and wetlands and their amenity and recreational value.
Why is keeping records of river flows important
Climate change is expected to impact very unevenly on river discharge patterns so keeping records is key go identify, quantify and interpret hydrological trends
What will identifying hydrological trends help in
The development of more effective ways of dealing with future flood and drought episode
How many measuring stations does the UKs dense gauging station network have
1,500 supported by secondary and temporary monitoring sites
Why is such a large number of measuring stations of discharge in the UK needed
Because the UK contains a multiplicity of most small river basins and is diverse in terms of its climate, topography, geology, land use and patterns of water usage
