The Water Cycle Flashcards
Is the world a closed or an open system?
Closed system driven by solar and gravitational potential energy
What is a closed system?
A system that has no external inputs or outputs
What two powers drive the hydrological cycle?
Solar energy: in the form of heat
Gravitational potential energy: causes rivers to flow downhill and precipitation to fall to the ground
What is a store?
Stores are reservoirs where water is held
What are the four main stores?
Oceans
Glaciers and ice sheets
Surface runoff (rivers, lakes, groundwater)
The atmosphere
How much water does the worlds Cryosphere hold?
69% of the worlds freshwater
How much water is held in groundwater?
30%
How much water is held in the biosphere?
Less than 1%
What is the global water budget?
The global water budget takes into account all the water that is held in stores and flows
What is a residence time?
The average time a molecule of water will spend in stores
What two water stores are un renewable?
Fossil water
Cryosphere
What is fossil water?
Ancient, deep groundwater made from wetter periods in the geological past
What is the Cryosphere?
Made up of snow and ice
Why is the Cryosphere non-renewable?
Because we have to wait for another Ice age
How much of the worlds water budget is accessible to humans?
1%
How much of the worlds water is in the oceans?
97.5%
How much of the worlds water is fresh water?
2.5%
How much of the worlds fresh water is in ice caps and glaciers?
69%
How much of the worlds fresh water is in groundwater?
30%
How much accessible surface water is in lakes?
52%
How much accessible surface water is soil moisture
38%
How much accessible surface water is in atmospheric water vapour?
8%
How much accessible surface water is in rivers?
1%
How much accessible surface water is in plants?
1%
What are the types of rainfall?
Conventional
Frontal
Relief/orographic
What is conventional rainfall?
A daily occurance. Most common in tropical climates and within rainforests
What is frontal rainfall?
Two air masses meet, depressions caused, mainly in the UK
What is relief/orographic rainfall?
When warm, moist air meets land of high relief (hills)
What are the factors effecting the drainage cycle?
Form (is it snow or rain etc)
Amount (amount of water)
Intensity (more intense=more floods)
Seasonality
Distribution, significant in very large drainage basins where tributaries are in different climates eg Nile
What are the seven different flows?
Interception
Infiltration
Percolation
Through-flow
Groundwater flow
Surface run-off
River or channel flow
What is interception? (Flow)
The retention of water by plants and soils which is subsequently evaporated or absorbed by the vegetation
What is infiltration? (Flow)
The process by which water soaks into, or is absorbed by, the soil
What is percolation? (Flow)
Transfer of water into permeable rocks
What is throughflow? (Flow)
The lateral transfer of water downslope through the soil
What is groundwater flow? (Flow)
The very slow transfer of percolated water through permeable of porous rocks
What is surface run-off? (Flow)
The movement of water that is unconfined by a channel across the surface of the ground
What is river or channel flow? (Flow)
Takes over as soon as the water enters a river or stream; the flow is confined within a channel
What are the four outputs?
Evaporation
Transpiration
Discharge
Evapo-transpiration
What is evaporation? ( outputs)
The process by which moisture is lost directly into the atmosphere from water surfaces, soil and rock
What is transpiration? (Outputs)
The biological process by which water is lost from plants through minute pores and transferee to the atmosphere
What is discharge (channel flow)? (Outputs)
Into another, larger drainage basin, a lake or the see
What is a drainage basin?
Is the area of land drained by a river and it’s tributaries, they vary in size from that of a small stream to a river like the Amazon
Are drainage basins open or closed systems?
Open system with external inputs and outputs
What are the physical factors effecting drainage basins?
Climate
Soils
Geology
Relief
Vegetation
How does climate effect a drainage basin?
Influences the type and amount of overall precipitation
Climate affects vegetation type
How do soils affect drainage basins?
Affects mainly surface runoff
They determine the amount of infiltration and throughflow
Affect the type of vegetation
How does geology affect drainage basins?
Affects subsurface processes eg percolation into aquifers
Indirectly affects soil formation
How does relief affect drainage basins?
Affects surface run off
Impacts the amount of precipitation
Slopes can affect the amount of runoff
How does vegetation affect a drainage basin?
Largely affects surface run off
Presence or absence of vegetation massively impacts interception and infiltration and also transpiration
How do humans affect the drainage basin cycle?
They accelerate processes (deforestation, changing land use) and creating new water storage (reservoirs or abstract water
It is mainly changes to…
Rivers and drainage
The character of the ground surface(shape, texture and covering) that accelerate processes
How does river management disrupt the drainage basin cycle?
Construction of storage reservoirs holds back river flows
How does deforestation affect drainage basins?
Clearance of trees reduces evapo transpiration, but increased infiltration and surface runoff (more floods)
How does agriculture affect drainage basins?
Soil compaction by livestock increases overland flow
Ploughing increases infiltration by loosening and aeration the soil
How does urbanisation effect drainage basins?
Tarmac increase the speed of surface run off by reducing percolation and infiltration
Drains deliver rainfall faster to rivers and streams
What’s happened to the Amazonia drainage basin as a result of human interference?
A lowering of humidities
Less precipitation
More surface run off and infiltration
More evaporation and less transpiration
More soil erosion, silt fed into rivers
What is the water budget?
The annual balance between precipitation, evapotranspiration and run off
Annual balance of inputs and outputs
What is the water budget equation?
P=E+R+/- S
Precipitation=evapotranspiration+Runoff+/- Storage over a year
What is a river regime?
The annual variation in the discharge or flow of a river at a particular point, usually measured in cumecs
What factors give a regime its specific character?
Size
Geology
Precipitation
Temperature
Water abstraction
Dams
What is a rising limb? (Hydrographs)
The discharge rising on the graph
What is lag time? (Hydrographs)
The time interval between peak rainfall and peak discharge
What’s the base flow? (Hydrographs)
The normal level of a river
What are the 9 factors that affect a Hydrograph?
Precipitation
Antecedent conditions
Vegetation
Relief
Soils
Geology
Human activity
Basin morphology (size of basin)
Drainage density
What is a flashy river?
Short lag time, high peak, steep rising limb
What is a flat river?
Long lag time, low peak, gently sloping bruising limb
What characteristics would a flashy river have when talking about Weather/climate?
Intense storm that exceeds the infiltration capacity of the soil. Rapid snowmelt as temperatures suddenly rise above zero. Low evaporation rates due to low temps
What characteristics would a flashy river have when talking about rock type?
Impermeable rocks, such as granite, which restrict infiltration and encourage rapid surface runoff
What characteristics would a flashy river have when talking about soils?
Low infiltration rate such as clay soils
What characteristics would a flashy river have when talking about relief?
High, steep slopes that promote surface runoff
What characteristics would a flashy river have when talking about basin size?
Small basins tend to have flashy hydrographs
What characteristics would a flashy river have when talking about shape?
Circular basins have shorter lag times
What characteristics would a flashy river have when talking about drainage density?
High drainage density means more streams and rivers per unit area, so water will move more quickly to the measuring point
What characteristics would a flashy river have when talking about pre- existing (antecedent) conditions?
Basin already wet from previous rain
What characteristics would a flashy river have when talking about vegetation?
Bare/low density, deciduous in winter, low levels of interception leading to more rapid runoff
What characteristics would a flashy river have when talking about human activity?
Urbanisation producing impermeable concrete and tarmac surfaces. Deforestation reduces interception
What characteristics would a steady river have when talking about weather/ climate?
High evaporation from high temps
Slow snowmelt
Steady rainfall
What characteristics would a steady river have when talking about rock type?
Permeable rocks such as limestone
What characteristics would a steady river have when talking about soils?
High infiltration, such as Sandy soils
What characteristics would a steady river have when talking about relief?
Low, gentle slopes that allow infiltration and percolation
What characteristics would a steady river have when talking about basin size?
Larger basins have more delayed hydrographs
What characteristics would a steady river have when talking about shape?
Elongated basins have delayed hydrographs
What characteristics would a steady river have when talking about drainage density?
Low drainage density means few streams and rivers per unit area, so water is more likely to enter the ground
What characteristics would a steady river have when talking about pre-existing (antecedent) conditions?
Basin dry , low water table
What characteristics would a steady river have when talking about vegetation?
Dense, deciduous in summer= higher interception
What characteristics would a steady river have when talking about human activity?
Low population density
Reforestation increases interception
What is drought?
The deficiency of water over an extended period of time
