The Water Cycle and Water Insecurity Glossary

Flashcards for vocabulary related to the water cycle and water insecurity.

Annual Fluxes

The total flows of water or carbon in a year.

Antecedent Moisture

Water from one storm that has not had time to drain away before more rain arrives.

Aquaculture

The breeding and harvesting of aquatic animals and plants.

Aquifer

A vast underground reservoir most commonly formed in rocks such as chalk and sandstone.

Base Flow

Also known as groundwater flow – slow-moving water that seeps into a river channel through rocks.

Basin-wide factors

Elements within a drainage basin – such as shape, relief, geology, vegetation, climate and land use – which determine what happens to the precipitation when it falls.

Catchment Area

Another name for drainage basin, because drainage basins ‘catch’ all of the precipitation falling within the watershed.

Channel Flow

The movement of water contained within a river channel.

Channel Storage

Water held in rivers and streams.

Closed System

Where there are no inputs or outputs of matter from an external source – i.e. where inputs and outputs are balanced.

Complex River Regimes

Where larger rivers cross several different relief and climatic zones, and therefore experience the effects of different seasonal climatic events – human factors can also contribute to their complexity, such as damming rivers for energy or irrigation.

Convectional Rainfall

When the ground warms up, evaporation takes place and the air above is heated and rises – associated with intense rainfall, electrical storms and thunder.

Cryosphere

The frozen part of the Earth’s hydrological system.

Cryosphere Loss

When thawing of the cryosphere becomes continuous and water flows away and is lost.

Deforestation

The removal of trees, leading to surface runoff and soil erosion and reducing soil water stores.

Discharge

The volume of water passing a certain point in the channel over a certain amount of time.

Domestic Conservation

Reducing the amount of water used around the home, such as repairing leaks or metering supplies.

Drainage basin

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

Drainage Density

Describes whether a river has many or few tributaries – dense drainage networks have many tributaries and carry water more efficiently.

Economic Scarcity

When people can’t afford water, even if it is available.

Effective Rainfall

The amount of precipitation remaining after evaporation.

El Niño

A situation occurring every 3-8 years where pressure systems and weather patterns reverse.

El Niño Southern Oscillation (ENSO)

The change in air pressure between ‘normal’ years and El Niño.

Energy Generation

The process of creating electric energy, such as thermal power generation and hydropower.

Evaporation

The conversion of water to vapour.

Evapotranspiration

The combined effect of evaporation and transpiration.

Field (or infiltration) capacity

The maximum capacity of moisture that a soil can hold.

Flash Flooding

When dry soil surfaces become waterlogged very quickly, causing rapid surface runoff.

Flood-return period

A statistical estimate of how often a flood of a certain magnitude is likely to occur, based on past flood levels (e.g. a 1-in-50-year or a 1-in-100-year flood).

Flux

The movement or transfer of carbon or water between stores.

Frontal Rainfall

Formed when warmer moist air meets colder Polar air – warmer air is forced to rise over the denser colder air, creating low-pressure and rain.

Gravitational Potential Energy

Ways in which water accelerates under gravity, thus transporting it to rivers and eventually to the sea.

Groundwater

Water that has percolated through rocks where it may be stored in aquifers for some time.

Groundwater Flow

Also known as base flow – slow-moving water that seeps into a river channel through rocks.

Groundwater Storage

Water held within permeable rocks (also known as an aquifer).

Hard-engineering

Human-made, artificial structures which are designed to protect the land from erosion.

Hydrological

The properties of water and how it is distributed on the Earth.

Infiltration

Water entering the topsoil – most common during slow or steady rainfall.

Input

A component in a system which comes from outside the system, such as precipitation into the drainage basin system.

Integrated Water Resource Management (IWRM)

A policy setting out that water resources are an integral component of ecosystems, a natural resource and a socio-economic good – promoting the co-ordinated management of water, land and related resources in a sustainable way.

Inter-Tropical Convergence Zone (ITCZ)

A band of cloud that occurs within tropical regions, caused by low pressure where the trade winds meet.

Interception

Temporary storage, as water is captured by plants, buildings and hard surfaces before reaching the soil.

Irrigation

The supply of water to the land by means of channels, streams and sprinklers in order to permit the growth of crops.

Jet Stream

A band of fast-moving air (located between 9 and 16 kilometres above the Earth) which determines the direction of depressions and their speed of movement.

La Niña

When the ‘normal’ pressure systems and weather patterns intensify and low pressure over the western Pacific becomes lower, and high pressure over the eastern Pacific higher.

Lag Time

The gap between the peak (maximum) rainfall and peak discharge (highest river level) on a storm hydrograph.

Low-Pressure System (Depression)

Caused when warm air rises and then cools and condenses, often causing prolonged and heavy rainfall.

Mega-Drought

A period of unusually low rainfall, lasting for decades or longer.

Meteorological

To do with the weather and processes in the atmosphere.

Monsoon Rains

The rains which accompany the monsoon wind when it blows from the southwest, and which bring rain across South and Southeast Asia between May and September.

Negative Feedback

When a change tends to reinforce a system, leading to stability.

Open System

A system with inputs from and outputs to other systems.

Orographic Rainfall

When warm, moist air is forced to rise over upland areas, causing the moisture to condense and create rainfall.

Output

An output from the system to the outside, such as evaporation or transpiration from a drainage basin system.

Overabstraction

The removal of too much water from groundwater reserves, leading to rivers drying up in times of low rainfall.

Percolation

The downward seepage of water through rock under gravity, especially on permeable rocks e.g. sandstone and chalk.

Physical Scarcity

When there is insufficient water to meet demand.

Players

Individuals, groups and organisations involved in making decisions that affect people and places, known collectively as stakeholders.

Positive Feedback

When a change leads to a decrease within a system and creates instability.

Potential Evapotranspiration (PE)

An estimate of the amount of water lost through evaporation and transpiration in any given period, depending on temperature and air humidity.

Precipitation

Moisture in any form, such as rain, snow, sleet and hail.

Rain-Shadow Effect

When orographic rainfall has occurred over an upland area, the area on the lee side of the hills will receive less rain because the air descends, warms and becomes drier.

Re-greening

The conversion of dry landscapes to productive farmland.

'Real value' prices

Prices which are adjusted for inflation or deflation and which take opportunity cost into consideration – they are considered to be more accurate than ‘nominal values’ when making economic decisions.

Recharge

When soil moisture levels increase as a result of precipitation following a dry period.

River Régime

The annual pattern of flow within a river – influenced by climatic conditions and the characteristics of the drainage basin (physical factors and human interventions).

Relief

The shape of the Earth’s surface with particular reference to changes in altitude and slope.

Reservoirs

Man-made lakes which store water.

Residence Time

The amount of time that water stays in the atmosphere.

Resilience

The ability of a system to ‘bounce back’ and survive.

Rising Limb

The line on a storm hydrograph which shows the discharge rise up to its peak discharge.

Rock Permeability

The extent to which rocks allow water to pass through.

Simple River Regimes

Where the river experiences a period of seasonally high discharge, followed by low discharge.

Smart Irrigation

The use of automated ‘smart’ technology which optimises water levels based upon factors such as soil moisture and weather forecasts.

Smart Planning

The integration of automated ‘smart’ technology during planning in order to improve efficiency and minimise costs.

Soft-Engineering

Attempts to work with natural processes in order to mitigate a flood risk.

Soil Characteristics

The types of soils and their features, such as whether they are permeable, dry or deep.

Soil Moisture

Water held within the soil.

Solar Energy

Energy from the sun.

Stem Flow

Water flowing down plant stems or drainpipes.

Store

An accumulation or quantity of water or carbon, such as lakes or groundwater in a drainage basin system.

Storm Hydrograph

A graph showing how a river responds to a particular storm – displaying precipitation and discharge over time.

Streamflow

Water that is flowing in a stream or river channel.

Surface Runoff (Overland Flow)

Flow over the surface of the land – affected by factors such as rock/soil type, storm intensity or if the ground is frozen.

Surface Storage

Any surface water stored in lakes, ponds and puddles.

Sustainable Drainage Systems (SuDS)

Techniques such as permeable pavements and infiltration basins which reduce surface runoff produced from rainfall.

System

A series of connecting processes, containing inputs and outputs, linked by stores and flows.

Thermohaline Circulation

An ocean current that produces both vertical and horizontal circulations of warm and cold water around the world’s oceans.

Throughflow

Also known as inter-flow; water seeping laterally through soil below the surface, but above the water table.

Throughput

The quantity of a material, such as water, that flows through a system or store.

Tipping Point

When a system changes from one state to another, irretrievably.

Transpiration

Water taken up by plants and transpired onto the leaf surface.

Tropical Rainforests

A biome which is located in the tropics and experiences an equatorial climate.

Tropospheric Rivers

Huge atmospheric flows of moisture.

UNECE

The United Nations Economic Commission for Europe, which aims to encourage economic integration across Europe.

Urbanisation

The increasing proportion of people living in towns and cities.

Vegetation Storage

Any moisture taken up by vegetation and held within plants.

Virtual Water

Water transferred by trading in crops and services that require large amounts of water for their production – for example, by importing a tonne of wheat from a water-rich area, a water- stressed area can save 1000 cubic metres of water.

Walker Cell

The circulation of air whereby upper atmospheric air moves eastwards, and surface air moves west across the Pacific, causing trade winds.

Water Balance Equation

A way of expressing the water budget. It balances precipitation (P), runoff/river discharge (Q), potential evapotranspiration (E) and soil moisture and groundwater storage (S). The equation is P = Q + E +/- S