Geography - hydrosphere, water cycles and water budgets

Hydrosphere

The interconnected system of all water on, under and above Earth’s surface.

Water cycle

The continuous movement of water between the atmosphere, land and oceans through processes such as evaporation, condensation, precipitation, infiltration, runoff and transpiration.

Global water budget

The balance between inputs, outputs and changes in water storage within the hydrosphere.

Water storage

The places where water is held, including oceans, groundwater, ice, lakes, rivers, the atmosphere and living organisms.

Freshwater

Water with very low concentrations of dissolved salts. It makes up approximately 3.5% of Earth’s total water.

Saltwater

Water containing high concentrations of dissolved salts, mainly found in oceans and seas. It makes up approximately 96.5% of Earth’s total water.

Evaporation

The process where liquid water changes into water vapour due to heating.

Condensation

The process where water vapour cools and changes into liquid water, forming clouds.

Precipitation

Water falling from the atmosphere to Earth’s surface as rain, snow, sleet or hail.

Infiltration

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

Runoff

Water flowing over the land surface into streams, rivers, lakes or oceans.

Transpiration

The release of water vapour from plants into the atmosphere.

Rainfall and water availability

Rainfall seasonality

The regular pattern of when rainfall usually occurs throughout the year.

Rainfall variability

The degree to which rainfall differs from the long-term average.

Drought

A prolonged period of below-average rainfall that can reduce water availability and affect agriculture, vegetation and ecosystems.

Uneven distribution of water

Although the total amount of water in Earth’s hydrological cycle is relatively fixed, water is unevenly distributed spatially and temporally.

El Niño and La Niña

El Niño

The warming phase of the Southern Oscillation (ENSO), characterised by weakened trade winds and unusually warm surface water in the central/eastern tropical Pacific. It generally reduces rainfall in eastern Australia and increases drought and bushfire risk.

La Niña

The cooling phase of ENSO, characterised by strengthened trade winds and unusually cool surface water in the eastern tropical Pacific. It generally increases rainfall in eastern Australia and increases flood risk.

Upwelling

The movement of cold, nutrient-rich deep ocean water towards the surface.

El Niño upwelling

Weakened trade winds reduce upwelling in the eastern Pacific, reducing the supply of nutrients to surface waters.

La Niña upwelling

Stronger trade winds increase upwelling of cold, nutrient-rich water in the eastern Pacific.

Human water use

Global water consumption

Approximately 70% of global freshwater withdrawals are used for agriculture, 20% for industry and 10% for domestic purposes.

Agricultural water use

Water used primarily for crop irrigation and livestock production.

Industrial water use

Water used in manufacturing, resource processing and cooling in power generation.

Domestic water use

Water used for drinking, sanitation, cleaning and other household purposes.

Earth system connections

Atmosphere–hydrosphere interaction

Solar energy drives evaporation from oceans and land, transferring water into the atmosphere where it can condense and return as precipitation.

Hydrosphere–biosphere interaction

Water provides organisms with an essential resource for photosynthesis, growth and survival.

Hydrosphere–geosphere interaction

Water causes weathering, erosion, transportation and deposition, helping shape Earth’s landforms.