Water Glossary

Hydrography

A graph that shows river discharge and rainfall over time

Flood

When the capacity of a river to transport water is exceeded and water flows over its banks

Base flow

The normal day to day discharge of the river

Storm flow

Storm runoff resulting from storm precipitation involving both surface and throughflow

Hydrological cycle

Cyclical movement of water from the ocean to the atmosphere

Bankfull discharge

Maximum discharge that a particular river channel is capable of carrying without flooding

Evaporation

When liquid water from a water store turns into gaseous water vapour

Rising limb

Part of storm hydrograph in which the discharge starts to rise

Falling limb

Part of hydrograph in which the discharge starts to decrease

Precipitation

Water vapour condenses and falls

Peak discharge

The time when the river reaches its highest flow

Cryosphere

Part of the earth system where water is frozen

Closed system

Nothing is gained or lost

Internal runoff

Water never reaches ocean

Peak rainfall

The point on a flood hydrograph when rainfall is at its greatest

External runoff

Water eventually reaches ocean

Lag time

Time interval between peak rainfall and peak discharge

Global water budget

Total amounts of inputs, outputs and stores of water

Atmosphere

An area which is often linked to atmospheric processes composed of gases such as nitrogen, oxygen, argon and carbon dioxide and is divided into five layers.

Biosphere

All living things on the earth

Residence time

How long water spends in a water store

Flux

Movement of water

Stem flow

Flow of water through plants

Vegetation storage

Water stored in vegetation

Drainage density

The total volume of water in a drainage basin

Bank full discharge

Maximum discharge of a river before flooding

River regime

Change in river discharge throughout the year

Simple regime

A river which experiences a period of seasonally high discharge, followed by low discharge

Complex regime

Larger rivers which cross several relief and climate zones

Hydrological drought

Where there is a water deficit in a particular place due to shortage of surface or subsurface water

Agricultural drought

Not enough water for crop growth

Meteorological drought

When precipitation has decreased significantly in an area, which can then cause hydrological drought

Socio-economic drought

When water demand for social and economic purposes exceeds water availability

Famine drought

Humanitarian crisis in which the widespread failure of agricultural systems leads to food shortages and famines with severe social, economic and environmental impacts

El Niño

Weakened trade winds over the pacific – drought in Northern Australia

La Niña

Strong trade winds over the pacific – S American drought

Walker cell

Driver of the trade winds

SOI

Southern oscillation index

SuDS

Sustainable drainage systems

Soak aways

Channel dug out to disperse surface water into the ground

Green roofs

Vegetation cover planted on top of buildings

Filter drains

Trenches filled with gravel to take runoff away

Over-abstraction

Rate of water abstraction exceeds replenishment

Ecosystem

Community of living creatures, that interact interdependently

Regulating

Benefits from natural regulation

Provisioning

Products that can be obtained from the ecosystem

Intense storm

Major low pressure, strong winds draw in moisture laden air masses, resulting in large volumes of rainfall in short spaces of time

Prolonged rainfall

Rainfall that lasts for many days

Extreme monsoonal rainfall

A monsoon season where large volumes of water continues to fall outside of usual season (May-September)

Snowmelt

Snow melts due to large temperature shifts in a region between summer and winter months

Water stress

Areas where there is less than 1700m3 of water available per person per year, causing temporary shortages

Water scarcity

Areas where there is less than 1000m3 of water available per person per year. Imbalance between supply and demands which can threaten food supplies, reduce economic development and causes environmental damage

Physical – there is insufficient water available to meet demand

Economic – there is water available but there is lack of wealth to exploit it

Water security

Sustainable access to clean and safe water

Desalinisation

Removing salt from seawater

Techno-fix

Innovation that helps to solve a human problem

Mega dams

Large scale dam

Hard engineering

Restriction of natural processes

Interception

Water captured by plants, buildings and hard surfaces

Soil moisutre

Water held in the soil

Throughflow

Water seeping laterally through the soil below the surface

Percolation

Seepage of water through rock under gravity

Base flow/groundwater flow

Slow moving water through the earth

Evapotranspiration

Combined effect of evaporation and transpiration

Gravitational potential energy

The influence of gravity acting downwards

Fossil water

Untapped ancient stores of freshwater

Soil recharge

Rainfall exceeds evaporation

Effective rainfall

Amount of precipitation remaining after evaporation

Field capacity

Maximum capacity of water that soil can hold

Flood return period

Estimate of how often a flod of a certain magnitude is likely to occur

Re-greening

Conversion of dry landscape to productive farmland

ENSO

El nino southern oscillation

Water gap

Difference between water availability depending on wealth

Salt water encroachment

Salt water drawn into aquifers when freshwater is pumped out

Hydrography

A graph that shows river discharge and rainfall over time

Flood

When the capacity of a river to transport water is exceeded and water flows over its banks

Base flow

The normal day to day discharge of the river

Storm flow

Storm runoff resulting from storm precipitation involving both surface and throughflow

Hydrological cycle

Cyclical movement of water from the ocean to the atmosphere

Bankfull discharge

Maximum discharge that a particular river channel is capable of carrying without flooding

Evaporation

When liquid water from a water store turns into gaseous water vapour

Rising limb

Part of storm hydrograph in which the discharge starts to rise

Falling limb

Part of hydrograph in which the discharge starts to decrease

Precipitation

Water vapour condenses and falls

Peak discharge

The time when the river reaches its highest flow

Cryosphere

Part of the earth system where water is frozen

Closed system

Nothing is gained or lost

Internal runoff

Water never reaches ocean

Peak rainfall

The point on a flood hydrograph when rainfall is at its greatest

External runoff

Water eventually reaches ocean

Lag time

Time interval between peak rainfall and peak discharge

Global water budget

Total amounts of inputs, outputs and stores of water

Atmosphere

An area which is often linked to atmospheric processes composed of gases such as nitrogen, oxygen, argon and carbon dioxide and is divided into five layers.

Biosphere

All living things on the earth

Residence time

How long water spends in a water store

Flux

Movement of water

Stem flow

Flow of water through plants

Vegetation storage

Water stored in vegetation