Systems and the Water Cycle

From CGP book, excludes Amazon and River Frome case studies

What are the 5 parts of a system

• inputs

• outputs

• flows/transfers

• stores/components

• boundaries

What are inputs

When matter or energy is added to the system

what are outputs

when matter or energy leaves the system

what are flows

when energy moves from one store to another w

what are stores

where matter or energy builds up

what are boundaries

the limits of the system

What is matter

any physical substance involved in a system like water and carbon

Example of a system in the water cycle

drainage basin

Describe a drainage basin system

water enters as rain (input)

the watershed is the boundary

some water is stored in the soil/vegetation

Water flows down the river

Water leaves the system when river meets the sea (output)

What is an open system

Both energy and matter can enter and leave, inputs and outputs of both

How is a drainage basin an open system

Energy from the sun enters and leaves the system and water is input as rain and output when a river discharges into the sea

What is a closed system

Matter can’t enter or leave and can only cycle between stores BUT energy can enter and leave

What is an example of a closed system

the carbon cycle

How is the carbon cycle a closed system

Energy is input from the sun by photosynthesis and output by respiration but the amount of carbon on earth remains the same as there are no inputs or outputs of matter

What happens to matter and energy in a closed system

energy can enter and exit a closed system, but matter is simply rearranged and remains constant within it.

What other type of system is there aside from open and closed

isolated where matter and energy can’t leave, but these don’t occur in nature

If the inputs and outputs in a system are balanced what is it in

equilibrium

What happens to flows and processes within a system in equilibrium

they continue but in the same way at all times so there are no overall changes to the system

What is a dynamic equilibrium

When inputs and outputs remain balanced on average

What is a positive feedback mechanism

When an initial change in the inputs and/or outputs leads to further change which amplifies that effect

What is a negative feedback mechanism

When an initial change triggers responses that counteract that change, keeping the system stable

How does a system respond to positive feedback

By increasing the effects of the change which moves the system further from previous state

How does a system respond to negative feedback

By decreasing the effects of the change which keeps the system closer to its original state

What is an example of a positive feedback loop within the carbon cycle

Temperatures rise

Ice sheets melt due to higher temp

Less ice cover means less of the sun’s energy is reflected

More of the sun’s energy absorbed by the earth

Temperatures continue to rise

Example of a negative feedback loop within the carbon cycle

Large amounts of CO2 emitted

Atmospheric CO2 increases

Extra CO2 increases plant growth

Plants remove and store more CO2 from atmosphere

Amount of CO2 in the atmosphere decreases

What type of system is the earth?

A closed system, energy can enter and leave but matter cannot

What are the 5 sub systems of the earth

Atmosphere

Cryosphere

Lithosphere

Hydrosphere

Biosphere

What is the cryosphere

The sub system which includes all of the parts of the earth where it is cold enough for water to freeze

What is the hydrosphere

The sub system which contains all of the water on earth, in either liquid (water), solid (ice) or gas (water vapour) form

What is the lithosphere

Outermost part of the earth which includes the crust and upper parts of the mantle

What is the biosphere

The sub system containing all of the earth’s living matter like plants, animals, bacteria, fungi etc

What is the atmosphere

The layer of gas between the earth’s surface and space, held in place by gravity

what makes the earth a cascading system?

energy and matter can move between the sub systems and the output of one is often the input of another

Changes that occur in one system can affect…

what happens in others

How much water does the hydrosphere hold

very approx 1.4 sextillion litres

What percentage of the earth’s water is freshwater

less than 3%

How much of the earth’s freshwater is frozen in the cryosphere

69%

How much of the earth’s freshwater is groundwater

30%

How much of the earth’s freshwater is liquid on the earth’s surface

0.3%

How much of the earth’s freshwater is stored as water vapour in the atmosphere

0.04%

What does water have to gain to melt or boil or lose to freeze and condense

energy

What is the global hydrological cycle

A closed system where the earth’s water is continuously cycled between different stores

Where can water be stored (5 stores)

Atmosphere

Cryosphere

Hydrosphere

Oceans

Terrestrial

what is atmospheric water

water found in the atmosphere, mainly as water vapour but some as liquid water in cloud droplets and ice crystals

What is cryosphere water

Water locked up on the earth’s surface as ice

What is the hydrosphere

A discontinuous layer of water on or near the earth’s surface which includes all liquid and frozen surface water, groundwater held in soil and rock and atmospheric water vapour

What is oceanic water

Water contained in the earth’s oceans and seas, excluding inland seas

What is terrestrial water

groundwater, soil moisture, lakes, wetlands and rivers

What are the 6 stores of terrestrial water

lakes, rivers, wetlands (surface)

Groundwater

Soil water

Biological water

What are rivers in the context of the water cycle

both a store and transfer of water

What does it mean for a river to be a store in the water cycle

It holds water temporarily as it travels through the landscape

what affects how long water is stored in a river

rainfall, gradient, rock type

What does it mean for a river to be a transfer in the water cycle?

A river acts as a transfer when it moves water from the land to other bodies like lakes or oceans

what is the largest river by discharge in the world

the Amazon

What is the average discharge of the Amazon river

about 215,000–230,000 m 3 /s

How much of the earth’s total river flow does the Amazon account for?

approx 1/5th

What is a lake

a collection of usually freshwater found in hollows on the land surface

How many lakes does Canada have?

2 million

What is the world’s largest lake

The Caspian sea

What is biological water

The water stored in all of the biomass of the world

How does biological water vary globally

it depends on vegetation cover so areas with dense rainforest store much more than deserts

What is a wetland

A permanent or temporary area of marsh, fen, peatland or water which is static or flowing where there is a dominance of vegetation

Where are wetland found

from the polar regions to the tropics and on every continent except from Antarctica

What is groundwater

water that collects in the pore spaces of rock

What is soil water

Water which is held together with air in unsaturated, upper weathered layers of the earth, important for weather, soil erosion and farming

What are the 5 stores of cryospheric water

sea ice

ice sheets

alpine glaciers

permafrost

icecaps

What are icecaps

thick layers of ice on land that are smaller than 50,000 km

What is permafrost

Ground soil, rock or organic material that remains at or below 0 degrees for at least 2 consecutive years

How thick is the permafrost

from 1m below ground to 1,500m

What are alpine glaciers

thick masses of ice found in deep valleys or upland hollows

What is sea ice

Frozen bits of oceanic water that don’t raise sea level as they are from oceanic water

What are ice shelves

platforms of ice that form when sea ice and glaciers drift into the ocean, icebergs are the bits that break off

what are ice sheets

A mass of glacial land over 50,000 km2

How much of the earth’s freshwater ice is within ice sheets

over 99%

How large is the Antarctic ice sheet

14 million km2

how do ice sheets form

when snow doesn’t melt entirely in the summer and new snow compresses the old snow to make it very dense

If the Antarctic ice sheet melted how much would the sea rise

60m

How much of the earth’s surface is covered by ocean

approx 72%

The ocean contains what percentage of the earth’s water

97% and only 5% of the oceans have been explored

What is the pH of the sea

Alkaline- 8.14 which has fallen from 8.25 due to rise in atmospheric carbon

Atmospheric water exists in how many states

all 3

what is the most common atmospheric water

a gas called water vapour

the amount of water vapour that can be held by the air depends on what

temperature, cold air can hold less

why is atmospheric water vapour important

it absorbs, reflects and and scatters incoming radiation which keeps the atmosphere at a temperature that can maintain life

How does water vapour and temperature have a positive feedback loop

a small increase in water vapour will lead to an increase in temperatures

increase in temperature causes increase in water vapour

what is a cloud

a visible mass of water droplets or ice crystals suspended in the atmosphere

how do clouds form

air in the lower layers of the earth’s atmosphere becoming saturated by either the cooling of the air or an increase in water vapour

what is evaporation

when liquid water changes state into gas, becoming water vapour

what are aquifers

Large reservoirs of freshwater deep below the rock. Commonly found in porous (contain air pockets) and permeable (allow water through) rocks e.g. chalk and sandstone

evaporation increases the amount of…

water stored in the atmosphere

how does the magnitude of evaporation vary by location and season

Evaporation levels high if there is lots of sun, warm, dry air and water

But low if there isn’t much sun, little available water and cool air which is already saturated

How can long term changes in the climate affect the magnitude of evaporation

during a glacial period, temperatures are very low so evaporation is too so higher temps from climate change increases

What is condensation

when water vapour changes state to become a liquid by losing energy to its surroundings and cooling down

what is a dew point

the temperature at which a gas will change to a liquid

what does the magnitude of condensation flows depend on

the amount of water vapour in the atmosphere and the temperature, for example if there is a lot of water vapour in the air and there is a rapid drop in temperature condensation will be high

precipitation is the main flow of water from

the atmosphere to the earth

What are the 4 main processes of the global water cycle

Evaporation

Condensation

Cloud formation and precipitation

Cryospheric processes

How do clouds become precipitation

when water droplets caused by air cooling down water vapour within clouds become big enough they fall as precipitation

What are the three main ways water vapour condenses

Contact with other air masses

Typography

Convection

How does contact with other air masses cause water vapour to condense

when warm air meets cool air, because it is less dense it is forced above the cool air and cools down as it rises, making it condense into droplets