Hydrological Characteristics (Cambridge International IGCSE Geography)

The Characteristics & Processes of Rivers

Spec point — 2.2.1 · Explain the main hydrological characteristics and processes which operate in rivers and drainage basins

Water on Earth

• Only 2.5% of the water on Earth is freshwater
• 68.7% of freshwater is stored in glaciers and ice sheets and 30% is groundwater
• The remaining 1.3% of freshwater is in rivers, soil moisture, lakes and the atmosphere
• All water is part of the hydrological cycle

Global water stores

Hydrological cycle

• The hydrological cycle is a closed system
• Water is constantly recycled through the system
• Within the hydrological cycle, there are stores and transfers (flows)

The Hydrological Cycle

Stores

• Stores are those places where water is held for some time. These include:

  • water in the atmosphere in the form of water vapour or water droplets in clouds
  • surface stores such as puddles, lakes, rivers and reservoirs
  • interception is how precipitation is prevented from reaching the ground, usually by being caught on leaves or branches
  • aquifers are permeable rocks such as limestone and sandstone which can hold water
  • ice and snow
  • seas and oceans

Flows (or transfers)

• Flows are how water is moved around the hydrological cycle. They include:

  • Evaporation

    • The change of water from a liquid to a gas (water vapour) due to heat from the sun

  • Condensation

    • When water cools and changes from water vapour into a liquid (water droplets), forming clouds

  • Transpiration

    • When plants release water vapour from their leaves

  • Evapotranspiration

    • The combined transfer of water vapour from the Earth's surface and plants

  • Precipitation

    • The transfer of water from the atmosphere to the Earth's surface in the form of hail, sleet, snow or rain

  • Overland flow

    • Any water flowing across the Earth's surface

  • Infiltration

    • When water moves down from the surface into the soil

  • Percolation

    • The transfer of water down into rocks and aquifers

  • Through flow

    • The movement of water through the soil between the groundwater store (water table) and the surface

  • Groundwater flow

    • The flow of water through rock

Exam Hint Remember that percolation and infiltration are not the same. Percolation happens after the water has infiltrated the soil.

Worked Example Which of the following statements are correct?

Tick two statements in the table below:

[2 marks]

	Tick
Overland flow occurs under the surface of the land
Water percolates from the surface into the soil
Groundwater flow moves water through the rocks
Water flows to the river on the surface through flow
Interception occurs when water vapour is evaporated
Infiltration occurs when water soaks into the soil

Final answer: Answer

• Groundwater flow moves water through the rocks [1 mark]
• Infiltration occurs when water soaks into the soil [1 mark]