The water cycle eq1 Flashcards
the hydrological cycle
the global hydrological cycle operares as a closed system (inputs, outputs, stores and flows) driven by solar energy and gravitational potential energy
closed system
occurs when there is a transfer of energy but not matter between the system and its surroundings (the inputs come from within the system).
The global hydrological cycle is a closed system
it is a continuous cycle, over a long period of time, nothing is gained or lost.
inputs in the hydrological cycle
the main input is precipitation
flows in the hydrological cycle
- interception
- infiltration
- percolation
- throughflow
- groundwater
- surface runoff
- river or channel flow
outputs
- evaporation
- transpiration
- discharge
interception
the retention of water by plants and soils which is subsequently evaporated or absorbed by the vegetation.
infiltration
the process by which water soaks into, or is absorbed by, the soil.
percolation
similar to infiltration, but a deeper transfer of water into permeable rocks
throughflow
the lateral transfer of water downslope through the soil
groundwater flow
the very slow transfer of percolated water through pervious (permeable) or porous rocks.
surface runoff
the movement of water that is unconfined by a channel across the surface of the ground.
river or channel flow
takes over as soon as the water enters a river or stream; the flow is confined within a channel
the water balance
The balance between inputs into a drainage basin and outputs. It is important for understanding the processes operating in a drainage basin and water balances throughout the year.
the water balance equation
precipitation=evapotranspiration +streamflow+/- storage
solar energy
The global circulation of water is driven by this eg. warmer temperatures leads to more evaporation
gravitational pull
On land gravitational potential energy is converted to kinetic energy. This keeps water moving around the system and holds water on Earth.
water budget
The annual (yearly) balance of fluxes ( flows) and the size of the water stores e.g oceans, atmosphere and biosphere.
water stores
A place where water can accumulate. It may be natural, such as a pond, lake, aquifer or river, or artificial, such as a tank, reservoir, channel or pipe. It may be located above or below the surface of the earth.
Is water a renewable resource?
yes but with fossil water as an exception
fossil water
Water that has been contained in an undisturbed space, usually ground water in an aquifer, for millennia or longer.
open system
Receives inputs from and transfers outputs of energy and matter to other systems
drainage basin
the area of land that is drained by a river and the smaller rivers and streams that flow into it. It is series of linked processes: inputs, flows and outputs.
What physical factors impact the drainage basin?
- Shape
- Relief- shape of land ( highland vs lowland)
- Geology- rock, permeability, porous?
- Vegetation
- Climate
- Land use
relief
steeply sided river valley means that gravity assists water, whereas gently sloping valleys produce longer lag time and slower surface runoff eg Sheffield
geology
- porous rock allows water through spaces
- pervious rock allows water to travel along joints and bedding places (limestone)
- both lack surface drainage and have high rates of infiltration
- impermeable rock impedes drainage
land use
lag time is higher in agricultural areas due to irrigation in comparison to land which has not been managed
atmosphere
heavy rainfall may exceed the infiltration capacity of the soil
vegetation
increases interception which will lead to a higher lag time. Increased evapotranspiration - Amazon rainforest
shape
circular drainage basin means that all points on the watershed are equidistant from the channel and this will lead to shorter lag time and higher peak discharge
elongated basins have longer lag time and low peak discharge
human factors affecting the drainage basin
- cloud seeding
- climate change
- urbanisation
- deforestation
- groundwater abstractation
- dam construction
- afforestation
cloud seeding
extra 5-15% precipitation, used in 50 countries, can be used to keep snow longer, can help with droughts.
Inputs particles into atmosphere to allow snowflakes or rainfall to form eg the Alps and Idaho
urbanisation
- infiltration decreases
- surface-runoff increases
results in flash flooding
anthropogenic climate change
temperature rising means evapotranspiration rates increase
deforestation
Without vegetation to intercept the rainfall, infiltration rates decrease and. direct overland flow increase, leading to shorter lag time and flooding. The roots of the trees also anchor the soil, reducing the chances of mudslide eg Freetown, Sierra Leone
afforestation
The roots of the trees are a vital part of the drainage basin system and create a network of channels through which water can infiltrate. Also, leaf decomposition is crutial for soil development. The wrong type of tree was used in Iceland so these processes could not occur.
dam construction
Dams are able to mitigate the effects of hydrological extremes. But they can reduce river discharge downstream and increase evaporation rates eg Grand Ethiopian Renaissanse Dam
groundwater abstractation
- stores reduce
- fossil water reduces
The amount of groundwater aquifers can hold is dependant on the permeability and porosity of the rock. The rate of recharge for them also differs eg Ogallala aquifer USA
What sequetial events of the drainage basin and impacted the most?
factors affecting the Amazon drainage basin
interception, evapotraspiration, surface runoff, infiltration, throughflow
the forest
factors affecting the Amazon drainage basin
There are around 40000 plant species, 1300 bird species, 3000 types of fish, 430 mammals and 2.5 million types of insects
evaporation
factors affecting the Amazon drainage basin
deforestation is reducing evapotranspiration
water is evaporated from the leaves
generates its own rainfall
type of rainfall
factors affecting the Amazon drainage basin
heavy local convectional rainfall and is an example of a self-sustaining cycle where water gets recycled into the tropical rainforest
agriculture
factors affecting the Amazon drainage basin
Agricultural practices tend to cause significant soil erosion and river siltation, as well as aquatic contamination with agrochemicals
impact of deforestation
factors affecting the Amazon drainage basin
Significantly reducing evapotranspiration while increasing runoff and river discharge eg Tocantins River
global water cycle
the annual balance between inputs (precipitation)and outputs (evapotranspiration and channel flow)
P=Q+E +/- S
precipitation = streamflow +evapotranspiration +/- changes in stores
soil moisdture surplus
soil mositure budget graph
soil water full, recharging groundwater, supplies field capacity
utilisation
soil mositure budget graph
more evapotranspiration from ground, water used up
soil moisture recharge
soil mositure budget graph
evapotranspiration decreasing, lower than precipitation, soil re-fills
maximum annual temperatures
soil mositure budget graph
maximum evapotransipiration and minimum precipitation, river levels fall
deficiency
soil mositure budget graph
water used up by high evapotranspiration and low precipitation, plants must adapt for droughts
field capacity
soil mositure budget graph
soil is full of water and cannot hold anymore
Ciaro, Egypt
- located in the North East of Egypt with close proximity to the Suez Canal
- it has a dry, hot climate and is dominated by desert
- the Nile river is its main water source
- the water is used for agriculture, industry and drinking
- the aswan dam could threaten water supply
Barrow, Alaska
- located on the North coast of Alaska
- it has a polar climate
- the main water source is the Isatkoak Resevior, which is mainly used for drinking
river regime
the annual pattern of flow of a river (its discharge)
simple regime
These sre where the river experiences a period of seasonally high discharge followed by low discharge. They are typically of rivers where the input dependa on glacial water, snowmelt or seasonal storms
2 types of river regime
- simple
- complex
complex regime
These are where large rivers cross several different relief and climate zones anf therefore experience the effects of different seasonal climate events. Human factors can also add to their complexity.
subdued
slow and no risk of flooding
flashy
there is a rapid increase in discharge and perhaps a risk of flooding
peak discharge
storm hydrograph
in redponse to rainfall in an event
bankfull discharge
storm hydrograph
water level reaches top of it’s channel
falling limb
storm hydrograph
decline in discharge
normal flow
storm hydrograph
long term storage sources such as permeable rock
lag time
storm hydrograph
difference in time between max precipitation and peak discharge
storm runoff
storm hydrograph
river flow derived from the immediate rainfall
approach segment
storm hydrograph
discharge of river before the storm
rising limb
storm hydrograph
increase in discharge in reponse to surface runoff and throughflow from a rainfall event
Drainage basin size
Conditions likely to produce a flashy hydrograph
Small basins: water will reach the channel rapidly, as it has a short distance to travel.
Drainage basin shape
Conditions likely to produce a flashy hydrograph
Circular basins: it will take less time for the water to reach the channel, as all the extremities are equidistant from the channel.
Drainage basin relief
Conditions likely to produce a flashy hydrograph
Steep slopes: water flows rapidly downhill and reaches the channel quickly.
Soil type
Conditions likely to produce a flashy hydrograph
Clay soil and thin soils: clay soils have low porosity and the grains swell when they absorb water, so water infiltrates slowly. Thin soil becomes saturated quickly.
Rock type
Conditions likely to produce a flashy hydrograph
Impermeable rocks: water cannot percolate into the rock, increasing surface runoff to rivers.
Drainage density
Conditions likely to produce a flashy hydrograph
High drainage density: a large number of surface streams per km2 means the storm water will reach the main channel rapidly.
Natural vegetation
Conditions likely to produce a flashy hydrograph
This grass: intercepts little water and there is little loss by evapotranspiration, so more water reaches the channel rapidly.
Land Use
Conditions likely to produce a flashy hydrograph
Urban: urban surfaces have more hard surfaces such as roads, and drains that carry the water rapidly and directly to the river.
Drainage basin size
Conditions likely to produce a subdued hydrograph
Large basins: water will take longer to reach the channel as it has a greater distance to travel.
Drainage basin shape
Conditions likely to produce a subdued hydrograph
Elongate basins: water will take a long time to reach the channel from the extremities of the drainage basin.
Soil type
Conditions likely to produce a subdued hydrograph
Sandy soils and thick soils: sandy soils have a high porosity, so the water can infiltrate. Deep soils allow more infiltration.
Drainage basin relief
Conditions likely to produce a subdued hydrograph
Gentle slopes: water can infiltrate into the ground and travel slowly to the channel through the soil and rock.
Rock type
Conditions likely to produce a subdued hydrograph
Permeable rocks: water percolates through pore spaces and fissures into the groundwater store.
Drainage density
Conditions likely to produce a subdued hydrograph
Low drainage density: a small number of surface streams per km2 means the water travels slowly through the soil and rocks to the river.
Land Use
Conditions likely to produce a subdued hydrograph
Rural: vegetated surfaces intercepts water and allow infiltration so water travels slowly to the river channel.
Natural vegetation
Conditions likely to produce a subdued hydrograph
Forest and woodland: intercepts water and has high rates of evapotranspiration, so less water reaches the channel, and more slowly.
