Glossary of Definitions - Water and Carbon Cycles - AQA Geography A-level

Acidification

Acidification

The gradual reduction of pH of the oceans, due to dissolving carbon dioxide from the atmosphere.

Anticyclone

A system of high pressure, causing high temperatures and unseasonably high evaporation rates.

Aquifer

A permeable or porous rock which stores water.

Biofuel

Burning crops and vegetation for electricity and heat.

Channel Flow

Water flowing in a rivulet, stream or river.

Choke Points

Points in the logistics of energy and fuel that are prone to restriction.

Convectional Precipitation

Solar radiation heats the air above the ground, causing it to rise, cool & condense forming precipitation (often as thunderstorms).

Cryosphere

The global water volume locked up within a frozen state (i.e. snow and ice).

Depression

A system of low pressure, with fronts of precipitation where low and high pressure air masses meet.

Desalination Plant

The conversion of seawater to freshwater, suitable for human consumption.

Desublimation

The change of state of water from gas to solid, without being a liquid (the opposite process to sublimation).

Drainage Basin

The area of land drained by a river and its tributaries.

Drainage Density

The total length of all rivers & streams divided by the area of the drainage basin.

Drought

An extended period of deficient rainfall relative to the statistical average for the region (UN).

Economic Water Scarcity

When water resources are available but insufficient economic wealth limits access to it.

ENSO Cycles

El Niño Southern Oscillations - naturally occurring phenomena that involves the movement of warm water in the Equatorial Pacific.

Evapotranspiration

The combined total moisture transferred from the Earth to the atmosphere, through evaporation and transpiration.

Frontal Precipitation

Where air masses of different temperatures meet at a front, one mass will be forced over another, causing precipitation beneath the front.

Global Hydrological Cycle

The continuous transfer of water between land, atmosphere and oceans. The Earth is a closed system.

Groundwater Flow

Water moving horizontally through permeable or porous rock due to gravity.

Hydrological Drought

Insufficient soil moisture to meet the needs of vegetation (crops, trees, plants) at a particular time.

Infiltration

The movement of water vertically through the pores in soil.

Integrated Drainage Basin Management

Establishing a frame of coordinated efforts between administrations (e.g. local government) and stakeholders (e.g businesses) to achieve balanced management of a basin (World Bank).

Interception

Raindrops are prevented from falling directly onto the ground, instead hitting the leaves of a tree.

Meteorological Drought

When long-term precipitation trends are below average.

Monsoon

The drastic variation between wet and dry seasons for sub-tropical areas, caused by a changed prevailing wind. Can lead to annual flooding.

Open System

A system affected by external flows and inputs (such as a drainage basin, or a sediment cell).

Percolation

Water moving vertically from soil into permeable rock.

Physical Water Scarcity

A physical lack of available freshwater which cannot meet demand.

Relief Precipitation

Precipitation caused when air masses are forced to rise over high land, determined by the relief/ morphology of the land.

Respiration

The process of converting glucose and oxygen into carbon dioxide and energy. Some organisms rely on respiration to survive.

River Regime

The pattern of river discharge over a year.

Runoff

Water flowing over the surface of the ground eg. after precipitation or snowmelt.

Salinisation

Where salt water contaminates freshwater stores or soils, creating saline conditions and reducing human use/ consumption.

Saltwater Encroachment

The movement of saltwater into freshwater aquifers or soils. This may be caused by sea level rise, storm surges or over-extraction.

Smart Irrigation

Providing crops with a water supply less than optimal, to make crops resistant to water shortages.

Storm Hydrograph

Variation of river discharge over a short period of time (days).

Sublimation

The change of state of water from solid to a gas, without being a liquid.

Thermohaline Circulation

The movement of volumes of seawater from cold deep water to warm water surface water.

Throughflow

Water moving horizontally through the soil, due to gravity.

Tipping Point

A critical threshold where any changes to a system after the tipping point are irreversible.

Transpiration

The process through which water evaporates through the stomata in plants' leaves.

Water Budget

The annual balance between inputs and outputs within a system.

Water Conservation

Strategies to reduce water usage and demand.

Water Recycling

The treatment and purification of waste water, to increase supply.

Water Scarcity

There are limited renewable water sources (between 500 and 1000 cubic metres per capita per year).

Water Security

The ability to protect and access a sustainable source to adequately meet demand.

Water Sharing Treaty

International agreements for transboundary sources.

Water Transfer

Hard engineering projects, such as pipelines or aqueducts, that divert water between basins to meet demand.

Watershed

The boundary between neighbouring drainage basins.