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Define stem flow
Water flows down the stems of plants and trees
Define surface runoff/overland flow
Rain flowing over the ground due to saturated soil or because rainfall exceeds soil’s infiltration capacity
Define throughfall
Water moving from vegetation to the ground
Define throughflow
Lateral movement of water down a slope into a river channel
Define groundwater/base flow
Downward and lateral movement of water within saturated rock
Define interception storage
Vegetation intercepts precipitation and stores it in leaves or branches
Define surface storage
Water collects above ground, mainly puddles in urban environments
Define soil water storage
Pores in soil are filled with water and air
Define groundwater storage
Water stored underground in permeable rocks
Define evapotranspiraton
Loss of water from vegetation through pores
Define river discharge
The volume of water in a river flowing past a certain point every second
70% of all water is salt water. True or False?
False: 97% salt water, 3% freshwater
How much of freshwater is stored in the cryosphere?
70%
Give 5 examples of cryospheric water storage
Sea ice, ice sheets, ice caps, glaciers, permafrost
Is the global water system open or closed?
Closed system
What percentage of freshwater is stored in the atmosphere?
3%
Define aquifer
Store of water underground
Describe the distribution of aquifers
Unrelated to above ground water prevalence. Major aquifer, North West Sahara system, is below a desert. Major systems under Europe e.g. western Russia and Germany
Describe the accessibility of aquifer systems
Needed in drier countries in Africa, but no economic access to equipment, heavy machinery required to extract water.
What is water vapour’s role in temperature control?
Absorbs reflects and scatters solar radiation
Why are the poles dry?
Cold air holds less water vapour. Opposite for warm tropical areas, so they are more humid
What are the slow and fast hydrological cycles?
Slow = Years/milennia e.g groundwater (residence time 10,000 years), oceans
Fast = Weeks/days e.g atmospheric moisture (10 days), rivers and lakes
How do we know the hydrosphere is in dynamic equilibrium?
Constant heating/cooling of the planet, but the amount of water doesn’t change, the storage does
Define latent heat
Energy taken from the environment to fuel evaporation which drops the surrounding temperature e.g feels cooler after rain.
Also the energy released during condensation
What are the 3 types of rainfall?
Relief rainfall = mountains, air condenses when forced higher & falls as rain. Scotland and Wales
Frontal rainfall = mid-latitude regions, cool and warm air meeting and the warm air forced over cool due to density difference. Warm air condenses as it rises. Heavy rain
Convectional rainfall = Air heated below by warm land/sea, rises then falls. Short, high volume downpours. Common in Europe
How is climate change driving water cycle storage changes?
Interglacials/glacials = during Ice Age , 1/3 of land area covered in glaciers and ice sheets, increased cryospheric storage
Global temp increase = melting cryospheric stores, increased volume of oceans and sea level rise
Warmer air = more water vapour storage
How are cryospheric process changing water cycle stores globally?
95% of water on earth locked in 2 ice sheets over Antarctica and Greenland
Snow falling on glaciers/ice sheets compressed and stored long-term.
Ice sheets and glaciers shrinking/melting.
If all polar ice sheets melt how much would sea levels rise by? Is this a positive or negative feedback loop?
60m, positive feedback loop
What percentage of land in the northern hemisphere is permafrost?
25%
How does deforestation (local scale) affect magnitude of stores?
Decreased interception, increased infiltration. Could cause water logging/overwhelm soil water store. Surface storage increase or surface runoff. River channel store increase
How do storms (local scale) affect water store magnitude?
Increased magnitude of all stores due to precipitation influx
Name 3 human processes that alter the magnitude of water stores
Deforestation, Urbanisation, Agriculture
Define permafrost
Ground that remains below 0 degrees celsius for over 2 years
Can vary from <1m to >1500m thick
Melting and releasing methane due to climate change
Define cryosphere
All parts of the water system where water is stored in solid form
What are ice sheets?
A mass of glacial land ice more than 50,000km squared.
Form where winter snow never melts fully, building layers of compressed snow
2 major ones cover Antarctica and Greenland. If the latter melted, sea levels would rise 6m
What is the water balance budget?
Balance between inputs and outputs in a drainage basin system.
What is the purpose of a flood hydrograph?
Shows the fluctuation in river discharge over a flood compared to the times of precipitation. Can be used to study the flood risk of a location
Define lag time
Time difference between peak rainfall and peak discharge. A shorter lag time = more damage.
What are the rising and falling limbs in a flood hydrograph?
Rising limb = saturated soil, increasing discharge
Falling limb = length of time for river discharge to reduce as runoff reduces. Slower than rising limb
What is base flow in a flood hydrograph?
Normal discharge of a river
What is the difference between a flashy and a subdued flood hydrograph?
Flashy = steeper graph, higher peak discharge. Impermeable rock and a narrow, straight, shallow river
Subdued = Low discharge peak, permeable rock and a river with meanders and a wide channel (flood relief channels)
What is a river regime?
Graph showing changes to a river’s discharge over a year in response to climactic changes with seasons.
What are simple and complex river regimes?
Simple = one high and low discharge period e.g. River Avon (high in winter, low in summer, steep decline in discharge but low all year)
Complex = several extremes of discharge e.g River Po, Italy. (high in winter, but also in summer due to melting Alps snow)
Name one long term, one seasonal and one short term change to the water cycle.
Long-term = climate change
Seasonal = snow melt
Short-term = storms
List 3 causes of the Boscastle flood
Intense precipitation (1.5 billion litres of rainwater)
Many tributaries meet at the river
2.5 hour lag time, no time to adapt
Steep sided valley, village at the bottom, increased runoff
No floodplain, permeable land
What were the consequences of the Boscastle flood?
Buildings affected (destroyed, washed away)
75 cars washed away
Damage to tourism and businesses
How does farming in HICs affect the water cycle?
Intensive farming removes vegetation decreasing interception and veg storage
Machinery compacts ground, reduced infiltration
Drainage systems increase infiltration and through flow
Local groundwater reduced for irrigation
What was Cape Town’s Day Zero
The day where Cape Town would run out of water for its 4.6 million residents, which they were 90 days away from in 2018
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