Introduction to Water Systems

Question 1

What is the water budget?

Answer 1

The water budget is a quantitative estimate of the amounts of water in storages + flows of the water cycle

Question 2

How much of the Earth’s surface us covered by water?

Answer 2

70%

Question 3

What percentage of all water is fresh water?

Answer 3

2.6%

Question 4

What percentage of freshwater is in polar ice caps and glaciers?

Answer 4

68.7% of freshwater

Question 5

What percentage of freshwater is in groundwater?

Answer 5

30.1% of freshwater

Question 6

What is the turnover time?

Answer 6

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

Question 7

What drives the water cycle and what does the water cycle drive?

Answer 7

Energy from solar radiation + the force of gravity drive the water cycle

The water cycle drives the world’s weather systems

Question 8

Name 5 transfers in the water cycle

Answer 8

• Advection (wind-blown movement)
• Flooding
• Surface run-ff
• Infiltration + percolation
• Stream flow + current

Question 9

Name the 3 transformations in the water cycle

Answer 9

• Evapotranspiration (liquid to water vapour)
• Condensation (water vapour to liquid)
• Freezing (into solid snow + ice)

Question 10

Name 7 storages in the water cycle

Answer 10

• oceans
• soil
• groundwater (aquifers)
• lakes
• rivers and streams
• atmosphere
• glaciers and ice caps

Question 11

Name 4 ways humans impact on the water cycle

Answer 11

> Withdrawals (domestic use, irrigation)
Discharges (adding pollutants)
Changing speed + direction of water flow
Diverting rivers

Question 12

How can humans change the speed and direction of water flow?

Answer 12

> 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

Question 13

Why do humans divert rivers?

Answer 13

> Many are diverted away from important areas to avoid flood damage
Some diverted towards dams to improve storage

Question 14

Name 2 examples of major changes in the water cycle caused by humans

Answer 14

> 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

Question 15

When do flash floods occur?

Answer 15

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

Question 16

What are surface currents?

Answer 16

• upper 400m of ocean
• moved by wind
• the Earth’s rotation deflects them + increases their circular movement

Question 17

What are deep water currents?

Answer 17

• make up 90% of ocean currents

- cause the oceanic conveyor belt

Question 18

How do deep water currents work?

Answer 18

• 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

Question 19

How can ocean currents affect climate?

Answer 19

• 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

Question 20

What is the Gulf Stream?

Answer 20

• 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