Hydrological cycle
movement of water between three storages
Role of oceans
74% total precipitation falls over oceans, 84% total evaporation comes from oceans
Evapotranspiration
Loss of water through evaporation + transpiration
Sublimation
Ice to water vapor
Condensation
Water vapor to liquid
Evaporation
Liquid to water vapor
Advection
Wind-blown movement of water
Precipiration
Movement of water from atmosphere to land and oceans
Melting
Solid snow and ice to liquid water
Freezing
Liquid form to solid form
Water on the surface may cause
Flooding, surface runoff, infiltration, percolation, currents
Flooding
Too much water to drain
Surface runoff
Movement of water over land’s surface
Infiltration
Movement of water from surface to soil
Percolation
Movement of water from soil to rocks
Currents
Movement of water in streams and rivers
Human impacts
Agriculture, deforestation, urbanisation
Deforestation impacts
Decline in vegetation cover, less interception, more ground compaction, more overland runoff, likelihood of floods
Interception
Because of grass water can’t reach soil
Ocean circulation systems
Are driven by differences in temperature and salinity
Salinity
How much salt there is
Ocean conveyor belt
Transports heat and energy around the world, affecting climate
Ocean conveyor belt role
Responsible for the transfer of heat from tropics to colder regions
Access to freshwater
Varies considerably, as some areas have year-round rainfall while others have water shortages
Physical water scarcity
water development is approaching, or exceeded unsustainable levels
Economic water scarcity
Where water is available locally but not accessible for most people for financial reasons
Effects of global warming
Many areas will become drier
Increasing demand for water is caused by
Population growth, societies becoming richer
Contamination and over-extraction of water
Overusing freshwater results in decline in quality because some water resources are non-renewable
How to conserve water
Construction of dams, water transfer schemes, desalination
Water resources and conflict
Conflict may arise over the use of water because of reduced availability of resources in lower basin countries
Lower basin
all precipitation flows to the same river
Example of water resources and conflict
Egypt and Ethiopia over the nile river
Demand for aquatic food resources
Continue to increase as the human population grows and as standards of living rise
Photosynthesis and aquatic food webs
Highest rate of productivity through photosynthesis is found in shallow seas
Comparison between terrestrial system and aquatic system
In terrestrial, most food is harvested from low tropic levels. In aquatic, most food is harvested in higher tropic levels.
Maximum sustainable yield
Largest amount of species that can be harvested without reducing annual replacement of biomass
Indigenous populations and sustainable yields
Hunts whales & seals within sustainable levels
Effects of developing modern fishing industry / technology
Falling fish stocks
Example of reducing impacts of modern fisihing
EU’s Common Fisheries Policy
EU’s Common Fisheries Policy
Set out regulations for size of catch permitted, size of fish allowed to be caught, size of nets, etc
Aquaculture
Cultivating aquatic organisms for food
Issues with aquaculture
Loss of habitat, pollution caused by the use of fish feed, antibiotics, spread of diseases within farmed fish
Freshwater pollution sources
Runoff, sewage, industrial discharge, solid domestic waste
Marine pollution physical sources
Rivers, pipelines, atmosphere, activities at sea
Types of aquatic pollutants
Organic material, inorganic plant nutrients, toxic metals, synthetic compounds, hot water, oil, radioactive pollution, invasive species, floating debris
Ways to test water quality
Dissolved oxygen, phosphate, nitrate, ammonia
Biodegradation of organic material
Utilizes oxygen, can lead to anoxic conditions
Anoxic
Oxygen-less
Results of biodegradation of organic material
Formation of methane, hydrogen sulfide, ammonia
Biochemical Oxygen Demand (BOD)
Measure of the amount of dissolved oxygen need to break down the organic material in water, can used to assess water pollution levels
Indicator species
Indirect measure of pollution and environmental degradation
Biotic indices
Indirect method of measuring pollution
What does biotic indices involve
Levels of tolerance, diversity, abundance of organisms
Trent biotic index
Based on the disappearance of certain indicator species as pollution increases
Eutrophication
The process by which a body of water, such as a lake or river, becomes enriched with nutrients, especially with nitrogen and phosphorus
Eutrophication can be caused by both human and natural causes
Yes
Process of eutrophication
Increase of nitrates or phosphates, rapid growth of algae, accumulation of dead organic matter, high rate of decomposition, lack of oxygen
Natural causes of eutrophication
Nutrients added from decomposing biomass, runoff from surrounding areas
Human causes of eutrophication
Runoff of fertilisers from agricultural land, domestic wastewater, untreated sewage
Positive feedback of eutrophication
Algae grow, block light, underwater plants die, create more nutrients as they decompose, more algae, further divergence from equilibrium
Negative feedback of eutrophication
Underwater plants die, dead organic matter increase, decomposers increase, faster decomposition, same quantity of dead organic matter
Impacts of eutrophication on ecosystem
Increase in biomass of algae, less light penetration to underwater plants, increase in bacteria and oxygen levels, decrease in biodiversity, length of food chain decreases
Impacts of eutrophication on society
Nitrate-enriched water = higher rates of stomach cancer, cost of treating nitrate-enriched water is expensive
Pollution management for altering human activity
Avoid spreading fertilisers in the winter, use organic fertilisers on agricultural fields, do not apply fertilisers to fields that are next to streams and rivers
Pollution management for regulating at point of emission
Sewage treatment processes that remove nitrates and phosphates from waste, only use washing machines with full load, reduce use of fertilisers
Pollution management for cleaning up and restoring
Pump air through lakes to avoid low-oxygen, reintroduce plant and animal species
Methods to reduce unsustainable fishing
International policies (EUCFP), national governments may establish marine parks and protected areas, consumers can make sure they buy certified fish
Dead zones
when there is not enough oxygen to support aquatic and marine life, can be result of eutrophication