Water systems Flashcards
Earths water budget
- 70% of Earths surface is covered by water
- 2.6% is freshwater
- 97% is saltwater
supply of fresh water
- 68.7% is water in polar ice caps
- 30.1% is in ground water
- 0.3% is in lakes, rivers and swamps
turnover time
the time it takes for a molecule of water to enter and leave part of the system
hydrological cycle
- consists of variety of storages and lows of water between the various storages
transfers
- advection
- flooding
- surface runoff
- infiltration
- streams flows and currents
transformations
- evapotransporation
- condensation
- freezing
storages include
- oceans
- soil
- groundwater
- lakes
- rivers and streams
- atmosphere
- glaciers and icecaps
human impact on the hydrological cycle
withdrawals - for domestic use, irrigation and industry
discharges - by adding pollutants to water from agriculture, fertiliser and sugar
- diverting rivers - diverted away to avoid flood damage
ocean current
movement of water both vertically and horizontally
surface currents
- upper 400m of the ocean
- moved by wind
- earths rotation deflects them and increases circular movement
deep water currents
- makes up 90% of ocean currents
- warm water holds less salt than cold water so is less dense and rises
- cold water holds more salt so is dense and sinks
cold currents
run from poles to the equator
warm currents
run from equator to the poles
ocean currents affects on local climate
- warm gulf stream moderates climate of north western europe
- cold benguela current moderates the climate of the Namibian desert
human use of freshwater
- domestic purposes
- agriculture and irrigation
- industry
- hydroelectric power generation
- transportation
sources of freshwater
- rivers
- streams
- resevoirs
- lakes
underground aquifiers
- layers of porous rock sandwiched between two layers of impermeable rock
- filled continuously by infiltration of precipitation
- water flow is very slow
issues with freshwater use
- climate change may be disrupting rainfall patterns
- underwater aquifiers are being exhausted
- irrigation often results in soil degradation
- industry releases pollutants into water bodies
solutions to freshwater issues
- increase freshwater supplies
- reducing domestic use of freshwater
- selecting drought resistant crops reduces need for irrigation
- industries regulated to remove pollutants from wastewater
marine ecosystems
- very biodiverse and have high stability and resilience
- 1/2 of all marine productivity is in continental regions above the continental shelf
continental shelf
- upwellings bring nutrient rich water up to the continental shelf
- light reaches shallows so producers can photosynthesise
fisheries
- 90% in oceans
- 10% in freshwater
- fisheries include shellfish and some vertebrae
- up to 500 million make livelihood off fisheries
- 3 billion gain 20% of their protein intake from fish
aquaculture
- people in MEDC’s eating less meat and eating more fish and veg
impacts of fish farms
- loss of habitats
- pollution
- spread of diseases
- escaped species include GM fish which outcompete others
fish supply becomes exhausted through
- commercial fishing is informed by new GPS navigation
- fishing fleets have become larger
- indiscriminate fishing gear takes all organisms
maximum sustainable yield
the highest amount that can be taken without depleting the stock
optimum sustainable yield
requires less effort and maximises difference between total revenue and total costs
biochemical oxygen demand
measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water
indicator species
show something about the environment by presence, absence or scarcity
biotic index
measures pollution by assaying the impact on species within the community
