geog wa3 water

Water stores

Places where water is contained. They are categorised into freshwater and saltwater stores.

Freshwater stores

Water stores that contain freshwater, such as glaciers, rivers, lakes, groundwater and soils.

Saltwater stores

Water stores that contain saltwater. The ocean is the main saltwater store.

Glacier

A large mass of ice that stores freshwater.

River

A natural flowing body of freshwater.

Lake

A large inland body of standing freshwater.

Groundwater

Water stored beneath the Earth's surface in soil and rocks.

Soil water

Water stored within the soil.

Ocean

A large body of saltwater covering most of the Earth's surface.

Spatial distribution

How water stores are spread across different places on Earth.

Freshwater availability

The amount of freshwater available for people to use in a country or area.

Hydrological cycle

The continuous movement of water around Earth through different processes, ensuring a continuous supply of water.

Renewable resource

A resource that is naturally replenished over time. Water is renewable because it is recycled by the hydrological cycle powered by the Sun.

Evaporation

The process where liquid water changes into water vapour due to heat from the Sun.

Condensation

The process where water vapour cools and changes into tiny water droplets to form clouds.

Precipitation

Water that falls from clouds to Earth as rain, snow or hail.

Surface water

Water found on Earth's surface, such as rivers and lakes.

Transpiration

The process where plants release water vapour into the atmosphere through their leaves.

Infiltration

The movement of water from the Earth's surface into the soil.

Percolation

The movement of water through the soil and its layers after infiltration by gravity and capillary forces.

Catchment area (Drainage basin)

An area of land where water collects when it rains, often bounded by hills.

Water budget

The balance between water entering and leaving a catchment area.

Water input

Processes that increase the amount of water in a catchment area, such as precipitation.

Water output

Processes that decrease the amount of water in a catchment area, such as evaporation.

Net change in water storage

The difference between water inputs and water outputs in a catchment area.

Water surplus

Occurs when water input is greater than water output.

Water deficit

Occurs when water input is less than water output.

Accessible freshwater

Freshwater that humans can reach and use.

70% of Earth's surface

Approximately 70% of Earth's surface is covered by water.

Freshwater percentage

Only 2.5% of Earth's water is freshwater.

Accessible freshwater percentage

Only 1.2% of Earth's freshwater is accessible for human use.

Readily available surface freshwater

Only 21.39% of surface freshwater is readily available for human use.

Why isn't freshwater always readily available?

There is only a limited amount of freshwater, it is unevenly distributed, and much of it is locked in glaciers, ice caps or deep underground.

What powers the hydrological cycle?

The Sun.

Why is water a renewable resource?

It is continuously recycled by the hydrological cycle.

Formula for water budget

Net Change in Water Storage = Water Input − Water Output.

Positive storage change

Occurs when water inputs are greater than water outputs, causing water levels to rise.

Negative storage change

Occurs when water outputs are greater than water inputs, causing water levels to fall.