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IB Geography : Freshwater - Coggle Diagram
IB Geography : Freshwater
1.0: Physical Processes and Characteristics
Drainage Basin: Area of land drained by a river and it's tributaries
Open System: A system with inputs and outputs
Can drain into the sea but can also be endorheic (closed) and drain into lakes/inland depressions
Upper Course
V Shaped Valleys + Interlocking spurs
As the small stream flows downhill steeply, the bedload will erode downwards and scrape away at the bottom of the channel --> vertical erosion deepens the bed --> Weathering and gravity wear away valley sides forcing material down the slope --> stream naturally follows depression in the landscape
Areas too hard to erode due to rock composition are wound around by the river to form interlocking spurs
Waterfalls + Steep-sided Gorges
As the river flows, hydraulic action erodes the soft rock but doesn’t erode the hard rock. This creates a steep drop which forms the waterfall as water flows down it.
Water carries load, which when dropped from the height hits the soft rock below. Abrasion from the rocks causes the riverbed directly below to deepen, creating the plunge pool
The hydraulic action from the fast flowing water erodes the soft rock beneath the hard rock, undercutting the hard rock and forming an overhang of hard rock.
The hard rock eventually becomes unstable and collapses into the plunge pool. The process repeats
The waterfall slowly erodes upstream, leaving behind a steep sided gorge.
Middle Course
Meander
Outside bend --> erosion; Inside bend --> deposition
Lower Course
Hydrological Cycle
Input/Output
Evapotranspiration
Evaporation: Liquid from above ground stores and rivers turning into gas
Precipitation: moisture falling from the sky
Flow
Channel Flow: water eventually flows through a river to the ocean
Infiltration: movement of water into soil
Groundwater discharge and Groundwater flow: movement of water through saturated ground
Percolation: water travels from unsaturated to saturated ground
Surface runoff: water moving aboveground
Transpiration: Liquid water evaporating from vegetation
Canopy Drip: when water intercepted by vegetation drips onto the ground
Store
Interception: when an object stops precipitation from reaching the ground
Ice storage: water held in glaciers and ice caps
Stemflow: water stored and flowing within the stems or trunks of a plant
Groundwater storage: water stored in saturated soil
Lake Storage/Ocean storage: water held above ground in rivers or seas
Atmospheric storage: water stored as water vapor in clouds
Soil Moisture storage: water stored in unsaturated soil
Closed System: A system with no inputs or outputs
Cryosphere: portions of earth where water is stored in its solid form in glaciers, sea/lake/river ice, snow cover.
Plays large role in hydrological cycles due to seasonal melting of ice. This plays a significant role in the global climate and response to global changes
River Discharge
Velocity of a River
Channel Shape
Hydraulic radius : ratio between area of the cross section of the river and the wetted perimeter
Larger hydraulic radii =less water in contact with wetted perimeter --> less friction in comparison to velocity
Affects the point of maximum velocity (fastest flow = thalweg)
Channel Gradient
Channel Roughness
A river flowing through a channel with more protrusions meets more resistance than one without.
Laminar Flow: Horizontal movement of water upstream to downstream. It is uncommon because it would require moving over sediment without disturbing it
Turbulent Flow: Most common. Consists of horizontal and vertical eddies moving downstream. Varies with energy left after overcoming friction (95% of energy used to overcome friction.)
Increased velocity --> Increased energy --> more energy available after overcoming friction --> more turbulent flow
Helical flow: movement of water side to side in a corkscrew motion
Erosion: Soil and rock particles are worn away and moved elsewhere by wind, water, or ice.
Corrosion/Abrasion: Wearing away of bank and bed by load carried (corrosion=process abrasion=result)
Increases with velocity. Dependent on concentration, hardness and resistance of rocks+bedroc
Attrition: Wearing away of the load carried through scraping against each other
Hydraulic Action: Air and water are forced into cracks of the rock causing it to break down
Accelerations of fluid and pressure drops can affect rate of hydraulic action
Corrosion/Solution: Removal of chemical ions by water.
Dependent on composition of rock and water as well as discharge and velocity
Hjulstrom Curve shows relationship between velocity and load size.
Capacity is the largest amount of debris a stream can carry
Competence is the diameter of the largest debris the stream carries
The smallest and largest particles require high velocities to lift them. Small particles are cohesive, and large particles are heavy
2.0: Storm Hydrographs and Factors affecting them
3.0 Water scarcity and quality
Agricultural activities
Salinisation
- The increased salinity (salt levels) of the land (THE SALINE SOLUTION?!?)
1.Agriculture clears land
(cut down indigenous trees that helped with interception)
More water from irrigation infiltrates into the ground -> percolates through the gaps -> water table rises
More evaporation of water can occur -> as water closer to the surface
Salt/minerals in water stay behind -> erosion of the land
Land can no longer be used for agricultural purposes -> farmers need to find new land
Case Study
The Murray-Darling
Causes of salinization:
Overwatering of crops -> salty water table rising -> brings the salt towards the surface
Deforestation of trees/native vegetation -> less water being collected + transpired -> higher water table
High temperatures / UV -> increased evaporation -> leaving more salts on surface of soil
Salinisation -> people abandon farmland + clearing out more land (cutting down trees/vegetation) -> more salination
Effects of salinization:
Plants/crops are unable to grow
House infrastructure is damaged as salt corrodes bricks at base of houses
Roads/tarmac crack due to the corrosion of salt (requiring 4x as much maintenance)
Stakeholders:
Farmers:
Loss of crops (lower yield) → lose money
Loss of land → less land to use for growing crops (less yield)
Usually have to clear more land and farm somewhere else
Residents/Civilians:
Less food to buy → risk of food shortage (demand exceeds supply) → lead to more food being imported → more expensive
Higher prices of food (vegetables, fruit etc.)
Loss of homes near the river (if salt erodes buildings) → decreased home value → lose money
Taxpayer money used on this by local government → less money can be utilised to help society
Government:
Spend more on maintenance of houses, roads,lands,infrastructure etc., grants for those affected
Higher cost
Money lost / impact on economy → as less food exported
More opportunity cost (money could have been spent on education/healthcare etc.) → limited budget
May have to spend more on importing food as well
Environmentalist:
Vegetation destroyed / cut down
Increased salinity harms ecosystem -> impacts animals/plants
Eutrophication
-
Fertilizer infiltrates ground when rainwater washes it down -> transporting it to river
Nutrients from fertiliser runoff cause algae to come to the top
More algal bloom
Less photosynthesis (plant underneath cannot photosynthesize to produce oxygen)
Only respiration can occur → even more oxygen in the water body lost
Anoxia (less oxygen)
Effects of eutrophication:
Ecosystem death
These lakes/ponds become “biological deadzones”
Death of aquatic animals
Water pollution
Stakeholders:
Farmers:
Excess use of pesticides/fertilisers → cause the fertilisers to seep into river
Less nearby water that is useable for irrigation/farming
Government:
More opportunity cost
Spend more on preserving ecosystems
Civilians:
Algae blooms in rivers are unsightly
Eutrophic lakes -> residents can no longer swim/fish etc.
Reduction in water quality due to water becoming anoxic
Environmentalist:
Concerned with the destruction of habitats/ecosystems
Concerned with the death of animals → impacts to food web etc.
Physical and Economical Water scarcity
Physical water scarcity: When demand for water by population, industry and environment exceed the natural water supply
Economical Water scarcity: When an area does not have the infrastructure or means necessary to procure water to fit demands of population, industry and environment
Water quantity: amount of water available measured in flow (litres per second)
Water quantity can be affected by level of water use - e.g. larger populations, more water demanding industries. It can also be lowered in times of drought/water scarcity Low water quantity can lead to communities having insufficient water.
Water quality: suitability of available water for use, assessed by physical, chemical and biological characteristics
Water quality can be affected by human activity such as agriculture and industries. Lack of water quality (e.g. contamination) can lead to sanitary issues.
Lakes and Aquifers
Aquifer: Underground body of rock or sediment serving as a store for groundwater
Contains connected and open spaces
Not subject to evaporation
Porous (can store water) and permeable (water can go in and out)
Unconfined aquifers are connected to the surface. Confined aquifers are trapped above or below beds less permeable than the aquifer itself
Artesian wells use confined aquifers to build up and generate water pressure so groundwater stored reaches the surface without need for pumping.
Water scarce:
fewer than 1,000 cubic meters of renewable freshwater available per person per year
Water stressed:
between 1,000 and 1,667 cubic meters available per person per year
Case Study
Water Scarcity in Iran
Climate change
Low precipitation levels, extended periods of drought
Temperatures surged to 66 degrees celsius
Water mismanagement
Unsustainable agricultural water usage (92% of water goes into agriculture)
Excessive dam construction and water diversion
Over extraction of groundwater (70% used up)
Water demanding heavy industries
Population growth
16.5 million in 1950 and expected to increase to 92 million by 2025
Urbanization leads to increased pressure on water sources as individuals become more concentrated in one area.
More water required for domestic use
Internationally shared water resources as a source for conflict
Case Study
Grand Ethiopian Renaissance Dam
Stakeholders
Ethiopia
Positives
Around 6000 megawatts of energy can be generated
Excess can be sold to other countries to generate income
Water collected can be used for irrigation
Negatives
Political conflicts
Expensive maintenance
Egypt
Negatives
Less water available
Conflicts between countries that share the Nile River
If the dam is filled too quickly the water supply in egypt will be significantly reduced and affect the electricity capacity of Aswan dam which is primarily responsible for irrigation and other water uses in egypt
Sudan
Positives
Receive power produced by the dam - dam is only 20km from Sudan’s border
The dam will stabilise the Nile’s flow, preventing flooding in Sudan, allowing them to consume more water and increase agricultural output → much of the water was previously consumed by Egypt
Negatives
Risk of conflict with Egypt or other affected communities downstream
Human Impacts
Costs $4.5 billion USD
Conflict with Ethiopia and Egypt regarding the dam use - Ethiopia insists it will only be for power but if they use it for irrigation Egypt will lose large amounts of water (distrust)
Physical Impacts
The dam upstream will likely decrease water supplied downstream → could lead to droughts in Egypt
85% of the Nile’s water comes from the Blue Nile - which Ethiopia is going to restrict the flow of water in order to fill up the dam (expected 25% reduction in water)
Largest Dam in Africa
Aims to help with Ethiopia's energy shortage and export energy to neighboring countries
Located in Ethiopia near its border with Sudan
In 2015, an agreement was signed between Egypt, Sudan and Ethiopia to evaluate the impact of the dam to prevent detriment to either party. This was never published due to lack of accurate information so tension still remains to this day
4.0 Water Management
Community Level Responses
Kenya Sand Dams: Cement, sand and rocks make up the dam. This can also act as a natural filter for water. The ground is layers with sand which can hold water as groundwater
Voluntary manpower --> mainly women and girls because water collection is mainly a female role.
Greenery and vegetation regrow due to fertile soil
Provides over 1000 people with a reliable source of water
Less chance of flooding
Gender equality:
Mostly girls and women volunteering as it is their responsibility to collect water
SDG:
Water management that doesn’t involve intense construction - usage of large machines and materials
Involves the wider community so everyone has a say
Ladakh: Glacial runoff harvesting - glacier melt is channeled to ice stupas, spraying onto them from within.
Billions of people rely on glacier melt and the river to survive (40% of glacier stored water has been used up)
Potential for interpersonal conflict for water
During spring when plants and humans require more water, the ice can melt
Could potentially grow more of them either downwards towards other communities or upwards to create chains
Increased dam building for multipurpose water schemes
Case Study
Lesotho Highlands water Project
South Africa
Costs
High water price which impacts the government and ultimately consumers
40% of water is lost due to leaks
Encourages dependence on Lesotho for a crucial resource
Conflict for water - due to high prices and scarcity of water
Benefits
40% of water from the Sehul River will be transferred to River Vaal in South Africa (Population: 60 million)
Increasing demand for water can be somewhat satisfied
Clean and sustainable water source
Can sustain the growing economic activity
Mitigate effects of periodic droughts.
Reduces acidity in the Vaal River Reservoir - restore balance
Lesotho
Costs
Encourages dependency on South Africa - may become overreliant on the funds from South Africa (single product/mono economy)
Polihali Dam will displace 17 villages and reduce agricultural land for 71 villages
Impact on local ecosystems: destruction of wetland, frequent flooding
Corruption within management has prevented money from reaching those affected
Large amounts of erosion - loss of valuable farmland
Benefits
Can generate income from selling water as a commodity which can be used to develop the country (provide 75% of GDP)
Can be used to generate electricity which can also be sold
Can provide Lesotho with hydroelectric power
Creation of jobs
Development of infrastructure such as roads and communication
Improved water supply (Population: 2 million)
Improved sanitation
Water surplus and low population means that water supply will not be affected
Transfer of water from Lesotho (water surplus and small population) to Johannesburg and surrounding regions (water deficit + high population density) through pipes, tunnels and dams
5 dams filled with water - biggest one (main one) is the Katse Dam
Lack in infrastructure to get water to locals who live in outskirts - and now water is being taken away instead of being made more accessible
200 million USD annually given to Lesotho - Generates 75% of profit
Population of South Africa: 60 million
Population of Lesotho: 2 million
Integrated Drainage Basin Management
Watershed - area of land drained by a certain body of water. Subwatersheds can make up a drainage basin.
Drainage basin - an area of land, drained by a river and its tributaries.
Serves as a habitat for animals and a place to promote biodiversity
Provides waterflow within watershed and further downstream
Sustain livelihoods + support income generation
Provide source of hydroelectric energy
Human activities
Urbanisation upstream → more surface runoff → more flooding
More agriculture → more pollutants → decreased water quality for communities downstream
Plan to protect watersheds and prevent human activities from influencing the system to large degrees. For example planting more trees to decrease the rate of surface runoff.
Case Study
The Murray Darling Basin
The issue
Lack of forestry - deforestation
Extreme variability in rivers
Periods of high salinity
Droughts - 1967 and 1996 to 2010
Murray Mouth closed - needed to be flooded to reopen
Acidic sediments in soil
The frequent building of dams meant that very little water made it down to the lower course, which affected the composition of soil in the flood plains, making soil sediments more acidic. Reconnecting the rivers to floodplains allows the soil to stay fertile so more crops and greenery can continue to flourish.
Solution: linking the Murray to the Adelaide
Part of IRBM is to hold back enough water to sustain the watershed - using just enough water so the rest can be left to prevent droughts
Allows water to be supplied even in times of drought -->Reliant on the Adelaide to supply water to the Murray → should the Adelaide ever experience periods of drought, the communities surrounding the Murray would also decline (full reliance on one source of water
Stakeholders
