Chapter 3
Water and its Spatial Distribution
States of water – solid, liquid, gas
Where is it found – water stores (places where water is contained, categorised as freshwater or
saltwater stores. Everything is freshwater except oceans, which is saltwater), oceans (large masses of
water, we have five oceans), glaciers (large masses of ice), lakes (water bodies surrounded by land),
rivers (natural wide flows of freshwater across the land), soil (topmost layer of Earth), groundwater
(found below the surface of the Earth).
What is the hydrological cycle – input (precipitation), flows (infiltration, percolation, surface runoff,
groundwater flow, channel flow), output (discharge into sea, evaporation, transpiration)
What is a water budget – in a catchment (water surplus, water deficit)
Net change in storage = Input (Precipitation) – Output (surface runoff, evaporation, transpiration)
Water surplus occurs when input is more than output. Deficit occurs when input is less than output.
Chapter 4
What relationship does water have with the environment and people?
1.
2.
3.
4.
How do variations in precipitation affect the availability of water? Floods, droughts.
How does water support river ecosystems?
How do people use water? Domestic, recreation, agriculture, industry.
How do human actions lead to water pollution and its associated impact?
How can water be managed sustainably? Improve water quality, reduce water consumption, improve
water technologies, import water.
Flood
Drought
Area receives a lot of rain over a sustained An area receives very little rain over a long
period of time.
period of time.
Large amount of water enters the river.
There is too little rainwater to replenish the
river.
The water level in the river rises quickly and The water level in the river drops gradually, until
overflows its banks.
it eventually runs dry.
River ecosystems – precipitation (rain) provides regular supply of water so organisms can live in them.
A food chain shows the relationships between organisms as energy is transferred through food.
Predators gain the energy they need to survive by eating their prey.
At the bottom of the food chain are aquatic plants known as phytoplankton. They obtain energy from
sunlight through photosynthesis and release oxygen into the water. Zooplankton, or small aquatic
animals, feed on phytoplankton. Insects feed on zooplankton and insects are eaten by fish. Humans
are at the top of the food chain.
How do people use water –
A) Recreation: activities for relaxation, such as kayaking or fishing leisurely
B) Agriculture: we use water to grow crops and rear animals for human consumption
C) Industry: factories require water to function, used to cool equipment, and water is also used
to generate electricity when it passes through turbines installed in dams
D) Pollution: harmful substances in the water. A threat to aquatic ecosystems
E) Sustainable use: we can manage it through improving water quality (cannot have pesticides,
radioactive material, garbage or petroleum in our wastewater), reducing water consumption,
improving water technologies (desalination – SG has four plants currently), and importing
water.
Chapter 5
What is the tropical climate – high mean annual temperature, high annual rainfall.
Tropical rainforests – found with in tropical climate, close to the equator. Evergreen, large variety of
plant species, vertical structure (emergent layer, canopy layer, undergrowth layer).
Mangroves – water with higher salinity, found in coastal areas, river mouths, sheltered environments.
Limited variety of plant species, relatively uniform height, horizontal zonation. Mangroves have
adapted to their environment through: salt-secreting leaves (removes salt from the water that their
roots have absorbed), salt-excluding roots (prevents roots from absorbing salt), aerial roots (pencil,
cone, prop, knee-bend roots). Aerial roots allow mangrove plants to directly absorb oxygen from the
air, instead of oxygen-poor soil. The roots also anchor the plants to the soft soil, preventing them from
getting uprooted and washed away by strong waves.
Require calm water conditions so that seedlings are able to take root and grow without getting washed
away. Accumulation of fine sediments, thus mangroves are found at coasts, shallow river mouths or
behind islands.
Tropical Climate – average weather conditions of a place over a long period of time, usually more than
30 years.
Rainforests – found in parts of the world which experience tropical climate. Central and South
America, West and Central Africa, South and Southeast Asia. They received abundant sunlight and
high rainfall, ideal conditions for plant growth – hence, they remain evergreen. This means they do
not shed all of their leaves at particular times of the year. Tropical trees continually grow new leaves
to replace older ones that die and fall off.
How have plants adapted – they adapt to compete for sunlight and high rainfall. This includes broad
leaves (large surface area, more photosynthesis), waxy leaves (reduce amount of water vapor that it
loses to the atmosphere), drip tips (small narrow points that go downwards), buttress roots (these
roots grow up to five metres above the ground surface, to support the very tall tree).