Sources of Fresh Water (Cambridge (CIE) IGCSE Environmental Management): Revision Note

What are the main sources of fresh water?

• Fresh water refers to water with low salt content, used by people for drinking, washing, farming and industry

  • Only a small percentage of Earth’s water is fresh water

• People obtain fresh water from four main sources:

  • Atmosphere

  • Surface water

  • Groundwater

  • Desalinated ocean water

Atmosphere: rain and snow

• Rain and snow come from precipitation, when water vapour in the atmosphere cools and falls to the Earth

  • Used directly by plants and stored in rivers, lakes and groundwater

• Many regions depend on seasonal rainfall for drinking water, farming and filling reservoirs

• Snow in mountains melts in warmer seasons

  • Meltwater feeds rivers and provides water during dry periods

Surface water: rivers, lakes and reservoirs

• Surface water is fresh water found above ground

Rivers

• Flow across the land and collect rainfall and meltwater

  • Used for drinking water, irrigation and hydroelectric power

Lakes

• Store large amounts of water in natural basins

  • Provide a reliable supply throughout the year

Reservoirs

• Reservoirs—artificial lakes created by building dams

  • Store water for cities, agriculture and industry

  • Help control flooding and maintain water supply during droughts

Groundwater: aquifers and wells

• Groundwater is stored below the Earth’s surface in soil and rock

Aquifers

• Aquifers—underground layers of rock that hold water

  • Filled by rainwater soaking into the ground

• Provide clean, filtered water for drinking but hard to access

Wells

• Wells are holes dug or drilled into the ground to reach aquifers

  • Communities pump water to the surface for home use, farming and livestock

Oceans: desalination plants

• Oceans contain salt water, which is not safe to drink

• Desalination is the process of removing salt from seawater to make fresh water

  • This can be done using heat (distillation) or membranes (reverse osmosis)

• A desalination plant is a large facility where machines remove salt from seawater to produce fresh drinking water

• They are usually found in coastal areas where freshwater supplies are limited

• They are useful in dry countries with little rainfall

  • Provides a reliable supply but uses large amounts of energy