Introduction to Water Systems Flashcards
What is the water budget?
The water budget is a quantitative estimate of the amounts of water in storages + flows of the water cycle
How much of the Earth’s surface us covered by water?
70%
What percentage of all water is fresh water?
2.6%
What percentage of freshwater is in polar ice caps and glaciers?
68.7% of freshwater
What percentage of freshwater is in groundwater?
30.1% of freshwater
What is the turnover time?
The time it takes for a molecule of water to enter and leave that part of the system
e. g. In oceans it takes 37,000 years
e. g. Atmosphere only 9 days
So water can be considered renewable // non-renewable depending on where it is stored
What drives the water cycle and what does the water cycle drive?
Energy from solar radiation + the force of gravity drive the water cycle
The water cycle drives the world’s weather systems
Name 5 transfers in the water cycle
- Advection (wind-blown movement)
- Flooding
- Surface run-ff
- Infiltration + percolation
- Stream flow + current
Name the 3 transformations in the water cycle
- Evapotranspiration (liquid to water vapour)
- Condensation (water vapour to liquid)
- Freezing (into solid snow + ice)
Name 7 storages in the water cycle
- oceans
- soil
- groundwater (aquifers)
- lakes
- rivers and streams
- atmosphere
- glaciers and ice caps
Name 4 ways humans impact on the water cycle
> Withdrawals (domestic use, irrigation)
Discharges (adding pollutants)
Changing speed + direction of water flow
Diverting rivers
How can humans change the speed and direction of water flow?
> In cities by building roads + channelling rivers underground // concreted areas
> Canalising: straightening large sections of rivers to facilitate more rapid flow through sensitive areas
> Dam,s barrages, making resevoirs
Why do humans divert rivers?
> Many are diverted away from important areas to avoid flood damage
Some diverted towards dams to improve storage
Name 2 examples of major changes in the water cycle caused by humans
> Aral Sea - intense irrigation has stopped river flow into the sea + lowered sea’s level (shrunk by 90% in area)
> Ganges basin - deforestation increases flooding as precipitation isn’t absorbed by vegetation
When do flash floods occur?
Flash floods occur when rainfall // snowmelt cannot infiltrate the soil + runs off on the surface. Either due to hard-baked soil in hot, dry areas // impermeable surfaces in cities
e.g. in Manila, capital of Philippines, 50% of the city was flooded in 2012 after record rainfall
What are surface currents?
- upper 400m of ocean
- moved by wind
- the Earth’s rotation deflects them + increases their circular movement
What are deep water currents?
- make up 90% of ocean currents
- cause the oceanic conveyor belt
How do deep water currents work?
- due to differences in water density caused by salt + temperature
- warm water can hold less salt that cold water so is less dense + rises
- cold water holds more salt, is denser so sinks
- when warm water rises, cold has to come up from depth to replace it (upwellings)
- When cold water rises, it has to be replaced by warm water (downwellings)
- in this way, water circulates
How can ocean currents affect climate?
- Water has a higher specific heat capacity than land
- This means water masses heat up + cool down more slowly than landmasses
- As a result, land close to seas + ocean has a mild climate w moderate winters + cool summers
What is the Gulf Stream?
- current in Atlantic Ocean that comes from Gulf of Mexico to Western Europe
- making it warmer
- As this water flows, some evaporates so by the time it reaches Scandinavian coasts it is much saltier + denser than surrounding sea water
- So sinks + returns in the conveyor belt back to where it started
