Chapter 4
Sustainable Management of Water

Unit 1
How Do Variations in Precipitation
Affect the Availability of Water?


  • the amount of precipitation that an area receives will determine how much water is available.
    This may result in:

What are Floods?

  • an overflow of a large amount of water onto what is normally a dry land
  • e.g. flash floods, river floods

What are Droughts?

  • a long period of little or no rainfall in a specific area
  • may last for months or even years, causing areas to become drier than normal
  • there may not be enough water available to replenish the amount used for human activities or lost through evaporation and transpiration
  • reservoirs and groundwater will start to dry up

River Floods

  • caused by sustained heavy rainfall or meltwater
  • the large amounts of rainwater and meltwater enter streams and tribunaries, which then flows into rivers
  • the water level in the river rises rapidly and eventually overflows the banks, flooding the surrounding areas

Flash Floods

  • caused by exceptionally heavy rainfall over a short period of time
  • often occur in dry areas where there is not enough soil of vegetation to allow rainwater to infiltrate the ground
  • most of the rainwater becomes surface runoff which quickly floods low-lying areas

Unit 2
How Does Water Support River Ecosystems?


  • precipitation provides a regular supply of water to rivers so that organisms can live in them

Food Chain

  • shows the relationships among organisms as energy is transferred through food
  • phytoplankton → zooplankton → insects → fish → humans

Unit 3
How Do People Use Water?


  • domestic
  • recreation
  • agriculture
  • industry

How is Water Used for Domestic Purposes?

  • using water for household activities
  • e.g. bathing, cooking and flushing the toilet

How is Water Used for Recreation?

  • water sports are highly dependent on water conditions and water quality
  • e.g. canoeing, sailing and sport fishing

How is Water Used for Industry?

  • to cool equipment in factories and power plants because they generate a lot of heat when they operate
  • to generate electricity when it passes through turbines installed in dams
  • as a cleaning agent in water fabrication (process of creating components for the electrical circuitry found in computers and mobile phones

How is Water Used for Agriculture?

  • accounts for the largest use of water worldwide
  • to grow crops and rear animals for human consumption
  • different animal and plant products require different amounts of water

Unit 4
How Do Human Actions Lead to Water Pollution and Its Associated Impact?


  • human activities often cause water pollution
  • water pollution occurs when harmful substances enter water bodies and cause water quality to fall
    water pollution poses a threat to aquatic ecosystems
  • pesticides and lead kill plants and poison animals

Unit 5
How Can Water Be Managed Sustainably?


Countries around the world have attempted to manage water resources by:

  • improving water quality
  • reducing water consumption
  • improving water technologies
  • importing water

How Do Countries Improve Water Quality?

  • water quality is determined by temperature, amount of dissolved oxygen, turbidity and pH
  • these factors affect how well aquatic plants can grow and the range of aquatic animals that can survive
  • countries implement laws to maintain or improve water quality
  • e.g industries are not allowed to release wastewater into water bodies without permission from the NEA

How Do Countries Reduce Water Consumption?

  • water consumption increase as a country's economy and population grow
  • raise awareness and promote water conservation with the community, schools and businesses
  • e.g. Water Efficiency Labelling Scheme (WELS) grades water appliance with a tick rating (water-efficient products)

How Do Countries Improve Water Technologies?

  • using technology to develop new ways of producing and conserving water
  • e.g. "Four National Taps" - water from local catchment, imported water, NEWater and desalinated water
  • use of artificial intelligence to treat wastewater - machine first analyses how polluted the wastewater is and then suggests the most effective method to treat it

How Do Countries Import Water?

  • SG imports water from MY (agreements will expire in 2061)
  • Kuwait imports water from Serbia due to its dry climate

NEWater and desalinated water

  • reliable water sources that do not depend on the weather
  • helps SG better cope with the threat of climate change
  • through desalination, PUB turns seawater into drinking water using advanced membrane technolgy
  • SG has four desalination plants
  • e.g. Keppel Marina East Desalination Plant

Desalination


- Step 1 - Pre-treatment
Seawater undergoes screening and filtration to remove fine particles and microorganisms


- Step 2 - Reverse Osmosis
Pre-treated water is pumped at high pressure through semi-permeable membranes to separate dissolved solids


- Step 3 - Condition + Disinfection
Water is disinfected, re-mineralised and made potable by adding chemicals (chlorine and fluoride)