IB ESS Topic 4 - Water and Aquatic Food Production Systems

water budget

a quantative estimate of the amount of water in different storages - the distribution of water on Earth - 97% salt, 3% fresh - mostly in ice caps and glaciers (68.7%)

Blue Planet

Earth's name due to the fact that 70% of Earth is covered with water

turnover times

how long it takes for a molecule of water to enter and leave that part of the hydrological system

(e.g. 37,000 years in the ocean; 16,000 years in ice caps; 300 years in groundwater; 12-20 days in rivers; 9 days in the atmosphere)

renewable water storages

atmospheric water and rivers - quickly replenished

middle ground (neither renewable or non-renewable) water storages

groundwater aquifers - take a long time to replenish (currently used unsustainably)

non-renewable water storages

oceans and icecaps - they would take 100s of years to replenish if used

the hydrological cycle

energy from solar radiation and the force of gravity drive the water cycle - which drives the world's weather systems

precipitation

rain

evaporation

liquid water changing state to gaseous water (water vapour)

evapotranspiration

the water lost by plants (especially trees in rainforests) through their leaves

infiltration

water sinking below the surface into the soil

surface run-off

water which does not infiltrate the soil, bu flows along the surface

condensation

gaseous water (water vapour) which turns to liquid - especially in clouds causing rain

advection

wind-blown movement

aquifer

groundwater - the water which is stored in permeable rocks between layers of impermeable bedrock - often drilled down into to create wells

withdrawals (a human effect on water systems)

water is used for domestic use, irrigation in agriculture and in industry

discharges (a human effect on water systems)

the addition of pollutants to water

e.g. chemicals from agriculture, fertilisers, sewage.

changing the flow (a human effect on water systems)

building roads and channeling water rivers underground or in concreted areas

canalising - straightening large sections of rivers

use of dams, barrages and dykes; making reservoirs

diverting flow (a human effect on water systems)

many rivers are led way from important/urbanised areas

some are led to dams to increase storage

flash flood

a sudden rush of water caused when rainwater or snowmelt cannot infiltrate the soil and runsoff on the surface

ocean currents

movements in the sea both vertically and horizontally - move in specific directions, and some have names

surface currents

the movement of the ocean in the upper 400m - movement is due to wind

deep water currents

aka thermohaline currents - caused by difference in temperature and salt concentration

hot water rises (less dense) - cold water sinks

water with a high salt concentration sinks (is more dense) - lower concentrations rise

the great oceanic conveyer belt

the huge oceanic currents which circulate the globe

climate

the weather patterns experienced by different locations

El Nino Southern Oscilations (ENSO)

trade winds weaken allowing warm waters to spread to the east

this causes warm are to rise in the middle of the Pacific

cold mineral rich water is pushed up in the middle of the Pacific causing fish to be found too far off shore for fishermen in small boats

Neutral phase (ENSO)

trade winds blow warm air and water from the east to the west Pacific

cold water is drawn up from the deep on the western coasts of the americas (carrying nutrient rich waters = fertile waters - many fish)

air rises in the western Pacific and circulate back to the eastern Pacific

La Nina (ENSO)

an overdrive of the neutral phase - the trade winds blow harder - the temperature difference between east and west increases

more evaporation and therefore rain in the west

the Walker Circulation

the winds which travel west across the Pacific, rise in the west (eastern coast of Australia), travel east again, and sink in the east (Western coast of the Americas)

saline

salt water - this is the majority of Earth's water

desalination plants

removing salt from saline water to create potable (drinking) water

requires a lot of energy - extra salty water is often released back into the ocean damaging sea-bottom ecosystems (the salt water sinks)

water crisis

the UN's term to describe the situation we are in today where up to 40% of humans alive do not have access to sufficient clean water

domestic water use

water used for drinking, washing and cleaning at home

agricultural water use

water used for irrigation (water for crops) and for animals to drink

industrial water use

water used for processes such as machine cooling, manufacturing and mining

20 litres of 40 litres?

the WHO (World Health Organisation) and Agenda 21 state that every human should have/needs access to this much water per day (on average)

much of the world has far less - other considerably more

water scarcity

how much water we have and how we use it

there may be enough water in an area, but then it is diverted for non-domestic use

sources of freshwater

surface freshwater - rivers, streams, reservoirs and lakes

underground aquifers

aquifer

a layer of porous rock sandwiched between two layers of impermeable rock

refills where the porous rock meets the surface as water infiltrates

(flow can be as little as 1-10m per centrury - therefore refilling is extremely slow)

aquitard

the impermeable rock above (upper) and below (lower) the permeable rock forming an aquifer

grey water

water used in the home for cleaning, brushing teeth, showering etc

often is not really dirty, but drains the same way as sewage

black water

sewage - the water containing human waste - may carry disease-causing bacteria or parasites

water wars

the conflict caused by dispute over water sources - often when sources are shared e.g. Israel, Gaza and Egypt

marine ecosystems

oceans, mangroves, estuaries, lagoons, coral reefs, deep ocean floor

very diverse and have high stability and resiliene

continental shelf

the extension of the continents under the seas and oceans - creates shallow water

important because:

- 50% of productivity in only 15% of its area

- upwellings bring nutirent-rich water to continental shelf

- higher light penetration/insolation

- countries can claim it as theirs to exploit and harvest

UNCLOS

The UN Convention on the Laws of the Sea - in 1982 they designated the continental shelf as belonging to the country from which they extend

phytoplankton

single-celled organisms that can photosynthesis and are the most important producer in in the oceans, producing 99% of primary productivty - crucial in supporting oceanic food webs

zooplankton

single-celled animals which feed off of phytplankton and their waste - crucial in supporting oceanic food webs

DOM

dead organic matter

waste created by living organisms as they grow and die

benthic

organisms living on or in the sea bed

pelagic

organisms living surrounded by water from above the sea bed to the surface

fishery

when fish are harvested in some way - includes capture of wild fish and aquaculture (fish farming)

90% is marine - 10% is freshwater

FAO

Food and Agriculture Organisation:

- more than 70% of world fisheries are fully exploited, in decline, seriously depleted or too low to allow recovery

aquaculture

the farming of aquatic organisms in both coastal and inland areas involving human intervention in the rearing process to enhance production (FAO)

benefits of fish

high in protein, contains important lipds (fats and oils), low in bad fats, provides

on average, people eat 20 kg of fish and only 8 kg of meat

vegetarian farmed fish

solution to sustainable aquaculture - the United States Department of Agriculture has proven that there are eight species of carnivorous fish which can gain enough nutrients on a diet excluding other fish

China's production of farmed fish

62% of all farmed fish - mostly carp or catfish - often grown in rice paddies (DOM and waste provides nutrients for the rcie)

rice - fish farming

a system whereby fish are reared in rice paddies - the fish eat insect larva and algae and produce waste which the rice uses as fertiliser

the tragedy of the commons

is an economic theory of a situation within a shared-resource system where individual users acting independently according to their own self-interest behave contrary to the common good of all users by depleting that resource through their collective action

e.g. individual countries using the ocean as a resource, and so over-exploitation is occuring

over-exploitation of fisheries

fishing at an unsustainable level - over-fishing (we are too good at catching fish)

- commercial fishing has high technology to aid in catching efficiency

- fishing fleeting are larger with modern refrigeration (to stay out longer)

- within a fishing fleet there are now also processing ships

- indiscriminate fishing gear catches all organisms whether they are the target species or not (by-catch)

- trawlers drag huge nets along the seabed destroying the benthic ecosystems

maximum sustainable yield (MSY)

the increase in natural capital that can be exploited each year without depleting the original stock or its potential to replenish itself - use of this leads to sustainability

SY = annual growth and recruitment - annual death and emigration

may lead to depletion of a population in bad breeding (recruitment) years