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IB Geography: FRESHWATER
Terms in this set (145)
All forms of moisture that reach the Earth's surface in different forms such as snow or rain
When it rains, moisture will collect on leave and branches and will be intercepted before it reaches the ground
Water storage on leaves and branches
When water is intercepted by leaves and branches and flows down tree trunks or stems
When water is held in lakes or puddles and cannot infiltrate into the soil
When water moves downwards through the soil through tiny pores
Soil moisture storage
Water is stored in the pores of the soil
When the water moves vertically down through the rock
When water from percolation is stored at depth in the rock
The loss of water directly from rivers or lakes or from vegetation
When water is removed from leaves into the atmosphere
Surface run off
When water does not infiltrate into the land, and water flows over land
When water moves sideways through the soil
The part of the river's discharge that is provided by groundwater seeping into the bed of the river
Runoff, evapotranspiration, leakage
Vegetation, surface, soil moisture, groundwater, channel storage
The snow and ice environment where freshwater is stored
How much freshwater is stored in the cryosphere?
66% of the world's freshwater
What percentage of water is used for agriculture?
What percentage of water is used for industry?
What percentage of water is used for human consumption and sanitation?
What percentage of the Earth's water is fresh?
Where is most of the world's water stored?
In the sea and is saline
What is the hydrological cycle?
The constant recycling of water between the sea, air and land
Why is the hydrological cycle a closed system?
Because no water is added or lost
Upper course of a river
V shaped valley, shallow, steep sides, interlocking spurs
Lower course of a river
Flat valley, deep, levees, oxbow lakes, meanders, floodplains
Why are drainage basins an open cycle?
They have inputs (where water enters the system as rain, snow etc) and outputs (where water leaves through the sea or evaporation)
The boundary between two drainage basins
The area drained by a river and its tributaries
The volume of water flowing over a certain point in a certain time, measure in cumecs
How to calculate discharge?
Velocity x cross sectional area
The ability of a channel to move water and sediment
The part of the CSA that is in contact with the banks and bed of the river
How to calculate hydraulic radius
Which types of channels are more effective at moving water?
Narrow, smooth and deep channels
What is the most effective shape?
A parabolic curve
Why are most rivers wide and shallow?
During a flood most of the river's energy is devoted to erosion and transport, so the channel becomes wider, and when the flow decreases, sediment is deposited on the bottom of the river
Which kind of rivers are best at at moving sediment?
Wide, shallow and rough channels
When are channels most efficient?
When the channels are at their "bankfull" discharge
What is a process?
A series of actions, changes or functions bringing about a result
What types of processes are there?
Erosion, deposition and transportation
When rocks hit against the bed and the banks of the river, wearing it down
When rocks hit against each other and wear each other down
Chemicals dissolved in the water corrode the bed, banks and sediment
Water smashing into the banks cause air to get trapped, and widens cracked
Deepens the valley, commonly found in the upper course
Widens the valley, found in the lower course, uses most of its energy for transportation
What factors affect the rate of erosion?
Load, velocity, gradient, geology, pH and humans
How does load affect the rate of erosion?
Heavier and sharper load means a greater potential for erosion
How does velocity affect the rate of erosion?
Greater velocity means more erosion
How does gradient affect the rate of erosion?
The higher, the more GPE, so the faster velocity and the more erosion
How does geology affect the rate of erosion?
The softer the rock, such as sand, the easier to erode
How does pH affect the rate of erosion?
Solution erosion is increased when water is acidic
How does humans affect the rate of erosion?
Deforestation, dams, bridges all interfere with natural flow and erosion
Large boulders are rolled along the bed
Fine particles are carried by the current
Small rocks bounce along the river bed
Tiny sediment particles dissolve in the water and are carried by the current
What factors affect the rate of transport?
Discharge and velocity
The largest particle a river can carry
How to calculate competence
V to the power of 6 e.g. V = 2 then C = 64cm3
The total quantity of sediment a river can carry
How to calculate capacity
V to the power of 3
What is the critical velocity?
The lowest velocity at which grains of a given size can be moved
What kind of sediment is found in the upper course?
Large angular boulders
What kind of sediment is found in the lower course?
Small rounded sediment
When are where does deposition occur?
The mouth of a river as it enters the sea, and the inside of a meander
What other factors affect the rate of deposition?
The flat either side of the river
Build up of sediment after a flood either side of a river
Example of a waterfall
High Force Water on the River Tees
What is an abandoned meander?
When a meander has been cut off
How is a meander formed?
When a river's thalweg runs through pools and riffles that aren't directly in line with each other. The water erodes these pools and makes them bigger and forms bends in the river
Formation of a waterfall
Band of hard rock followed by soft rock........
Shallow, wide, high velocity, steep water surface gradient, coarse grained bed material
Deep, narrow, low velocity, gentle water surface gradient, fine grained bed material
The faster part of the river
Types of transfers (6)
Stemflow, infiltration, percolation, through flow, surface run off, groundwater flow
Types of stores (4)
Interception by vegetation, surface storage, soil moisture storage, groundwater storage
Types of outputs (3)
Transpiration, evapotranspiration, river carrying water to the sea
Factors affecting discharge (7)
Temperature, rainfall and previous weather conditions, soil/rock type, land use, relief, seasonality, size and shape of drainage basin
How does high temperature affect discharge?
Increases the rate of transpiration so less output to channel, also increases snow melt
How does slow light rainfall affect discharge?
Most water infiltrates, and is stored, reducing surface run off to river, so discharge is not affected much
How does heavy prolonged rainfall affect discharge?
Pores in the land fill quickly causing overland flow (when water doesn't infiltrate into the soil as it is too saturated)
What is infiltration capacity?
The maximum rate at which rain can be absorbed by soil
What does antecedent moisture mean?
Previous weather conditions
How does antecedent soil moisture affect discharge?
If the soil is already saturated, then infiltration levels will be low and surface runoff will be high
The amount of water that can physically be held in the soil after excess water drains away
The border between the unsaturated zone and the saturated zone
How does permeable/porous rock type affect discharge?
With permeable rock, water can be absorbed and therefore surface runoff is decreased
How does impermeable rock affect discharge?
There will be large amounts of surface runoff
Example of porous rock
Example of impermeable rock
Example of permeable rock
Granite with cracks or faults
How does relief affect discharge?
High land means more rainfall and lower temperatures, so less evaporation. Also steep slopes cause faster surface runoff
How does urbanisation affect discharge?
Smooth impermeable surfaces, less vegetation to store water, less evapotranspiration, sewers and drains mean a direct flow of water to river channel
When sewers and drains cause a direct route to the river and increase discharge
How do bridges affect discharge?
Bridges restrict the width of a channel and therefore reduce the bankfull capacity
How does deforestation affect discharge?
Lots of plants and trees mean more interception as water is prevented from reaching the ground quickly, so deforestation will increase the discharge
Which factor has the greatest impact on discharge?
How does seasonality affect discharge?
Spring: snow melt, summer: monsoon flood, wet seasons: soil becomes saturated
How does a small size of drainage base affect discharge?
Smaller drainage basins respond quicker to rainfall conditions
How does a larger drainage basin affect discharge?
It takes longer for the lower part of the river to respond to an event in the upper course
How does the shape of a drainage basin affect discharge?
Circular basins respond more quickly thats linear basins
Flashy response hydro graph
Steep rising and falling limb, overland flow is maximised
Lagged response hydrograph
Shallow rising and falling limb, infiltration os maximised
What is an Integrated Drainage Basin Management (IDBM)?
Involves all the stakeholders in the drainage basin planning to develop and agreed set of policies so everyone receives what they need
What factors could an IDBM focus on?
Sustainable development, access to energy, healthy ecosystems, poverty alleviation, gender equality
What is physical water scarcity?
When there physically isn't enough water for everyone
Physical water scarcity definition
When water consumption exceed 60% of the useable supply
What is economic water scarcity?
Where a country physically has enough water to go around, but the water needs processing or transporting to be used, which the country doesn't have enough money for
What is an aquifer?
A layer of permeable rock that contains large volumes of groundwater
Water stored deep in the rock, below the water table and in the saturated zone
Where is the largest chalk aquifer in the UK?
How can groundwater be recharged?
Infiltration, seepage from rivers, or irrigation
How can groundwater be lost?
Evapotranspiration, or taken out through wells
Why are aquifers useful?
They are not subject to changes in the local weather and store a lot of water
Maximum sustainable yield
The largest amount of water that can be taken from a resource without depleting the original source or potential for replenishment
Ways the water is moved about in the drainage basin: infiltration, throughflow, overland flow, base flow
The amount of water the soil can hold
Leaves and twigs are carried on the surface of the river
Factors affecting erosion
Load, velocity, gradient, geology, pH, human impact
How might humans increase erosion?
Deforestation, dams and bridges interfere with the natural flow of a river and frequently end up increasing the rate of erosion
Critical erosion velocity
The lowest velocity at which grains of a given size can be moved
The annual variation in the flow of a river
Factor affecting the river regime
Amount and nature of precipitation, local rocks (permeability and porosity) and amount and type of vegetation cover
How are deltas formed?
When a river reaches a large body of water it loses energy and deposits what it was carrying
How does salinity affect delta formation?
Salt makes the clay particles clump together, making them heavier and more likely to be deposited
Main distributaries branch out radially e.g. Nile delta
A pointed delta formed by a dominant channel
Birds foot delta
Long projecting fingers which grow at the end of distributaries e.g. Mississippi delta
How can an aquifer be artificially recharged?
By creating a recharge basin, or pump water down the bore hole
What can be done to increase flood warnings?
- Better forecast of rainfall
- Better sharing of information
What urbanising factors can have hydrological effects?
- Construction of houses and streets
- Construction of storm drains and channel improvements
Decreased evapotranspiration and interception, increased stream sedimentation
Construction of homes and streets
Decreased porosity, decreased run off time
Construction of storm drains and channel improvements
Local relief from flooding may effect downstream
How can rivers be artificially modified to increase the flow of water?
Widening, channel straightening, artificial levees
Physical water scarcity
When water consumption exceeds 60% of the usable supply
How can countries overcome physical water scarcity?
They can import their food and invest in desalinisation plants
Economic water scarcity
When a country has enough water but doesn't have the additional transport or storage resources required
An extended period of dry weather
Integrated Drainage Basin Management: aims to deliver sustainable use of the world's water and meet everybody's needs
THIS SET IS OFTEN IN FOLDERS WITH...
IB Geography: CHANGING POPULATION
IB Geography: EXTREME ENVIRONMENTS
IB Geography: GEOPHYSICAL HAZARDS
IB Geography: FRESHWATER (Three Gorges Dam)
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