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aerated shower head
Aerated shower head

An aerated shower head uses a mix of water and air to produce a flow that feels strong but can save up to 60% of water compared to an average shower.

archaeological losses

The loss of any evidence of past human activities such as buildings, graves and tools. Flooding an area to build a reservoir is one way archaeological evidence may be lost.

average annual weekly demand

The cumulative demand in a year, divided by the number of weeks in the year.

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cistern displacement device
Using water at home

Saving water with each flush involves putting a water displacement device (also called a cistern displacement device) into the toilet cistern. This takes up space that would otherwise be occupied by water and means that less water is available for each flush. The most common cistern displacement devices are called a Hippo (which saves up to 3 litres a flush) and a Save-a-Flush (which saves 1 litre a flush).

climate change

Any long-term significant change in the 'average weather' that a region experiences. Experts have predicted that the UK climate is changing. It is likely that winters will become wetter and milder, summers will get hotter and drier and there will be an increase in extreme weather.

compensation (flow)

The volume of water that must be released from a reservoir into the river downstream of the dam. This release is usually made via a pipe that runs through the dam and ensures that the river downstream of the dam continues to flow even though it has been blocked by the dam.

commercial use
Using water in industry

The volume of water used by businesses like factories, shops and offices.


See demand.

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A barrier built across a river to block the flow and raise the water level. The water stored behind the dam is called a reservoir.

dam storage
Dam storage

The volume of water (usually measured in megalitres (Ml)) that is held behind a dam.

DEFRA (or Defra)

The government Department for Environment, Food and Rural Affairs.


The total volume of water used by households and businesses. People use more water in hot, dry weather, so demand is higher during the summer than it is in winter.

demand pattern

A demand pattern consists of a series of weekly factors that show the way that demand typically varies through the year.  Where the figure is greater than 1, the demand for that week is higher than average; this is usually the case during the summer.  During the winter demand is usually lower than average, leading to the demand profile for these weeks being less than 1.  Weekly demand is calculated by multiplying the weekly demand pattern factor by average annual demand.

dual flush device
Dual flush

Many modern toilets feature a dual flush option to help save water. A split flush button gives the user the choice of pressing a small button or a large button depending on how much water is required to clear the toilet bowl. If you don’t want to change your old toilet for a new one a dual flush device is something that can be fitted to older style "single flush" toilets that then allows a choice of a large or small flush to be made.

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environmental impact

The effect an activity or development has on the environment. For example, increasing the height of a dam will have an environmental impact because it will result in more land being flooded and less land being available for the people, animals and plants that live nearby.

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habitat loss

The loss of an environment where a plant or animal normally lives.

hectare (ha)

A hectare is equal to 10,000 square metres which is an area equal to 100 by 100 metres (1 ha = 10,000 m²).

hose trigger gun
Hose with trigger gun

An on/off trigger that allows a hose to be switched off when not needed, thus saving water.

household use

The amount of water a household uses, measured in litres/person/day.

hydroelectric power (HEP)

The generation of power by water flowing through a turbine.

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River inflow

The volume of water flowing into the reservoir from rivers, leats and surrounding land.

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A man-made water channel.

leat inflow

See inflow.

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megalitre (Ml)

A megalitre is 1 million litres (1 Ml = 1,000,000 l). An Olympic sized swimming pool contains approximately 2.5 Ml.

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The total number of people living in a particular country, area or place.

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A natural or artificial lake storing water which is usually used to supply a city or other area.

river inflow

See inflow.

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Water which overflows from a reservoir via the spillway when the reservoir is full.


The structure in a reservoir which is designed to allow water to flow out of the reservoir when it is full (see Spill). Its function is similar to the overflow in a bath or a sink.


See dam storage

surface area of reservoir

The area of a reservoir surface when it is full.

sustainable development

Defined by DEFRA as "development which enables all people throughout the world to satisfy their basic needs and enjoy a better quality of life without compromising the quality of life of future generations."

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water butt
Water butts

A large container for collecting rain which can then be used for things like watering plants and washing cars.

water saving - bath

Filling a bath uses an average of 80 litres of water. This is a huge amount to soak in and then simply throw away. Why not try cutting down on the amount of water in your bath? Using more than it takes to cover your body isn’t necessary and will simply create extra waste.

water saving - washing car

Try saving water by always using a trigger hose or a bucket when washing your car.

water saving - cleaning teeth

It would use far less water to only run the tap when wetting a toothbrush at the start and to rinse. How about turning the tap on and off when cleaning your teeth?

water saving - dishwasher

More modern machines will wash dishes effectively with far less water however, even keeping an old machine but making sure it is only used for full loads would save water and energy. Is a dishwasher more effective than doing all the washing up by hand?

water saving - kitchen sink

A washing up bowl will use less water than filling the sink bowl and has the benefit that water used in it for washing vegetables and the like can then be used to water your garden plants rather than just go down the plug!

water saving - shower

Remember, spending slightly less time in the shower will save hot water as well as the energy used to heat it!

water saving - toilet

Many houses still have a standard single flush toilet with a 9 litre cistern. A single toilet flush mechanism is one that empties all the water held in the toilet cistern at once when the flush handle is pressed. A cistern is the part of the toilet that holds the volume of water that is then used to flush the bowl. Cisterns have various capacities; older cisterns used to be 13 litres or 9 litres in volume but more modern ones are now 6 litres or 4 litres.

water saving - washing hands

How about making sure that the people in your household put the plug in when washing their hands in the sink rather than under running water from an open tap?

water saving - washing machine

More modern machines will wash clothes effectively with far less water however, even keeping an old machine but making sure it is only used for full loads would save water and energy.

water saving - watering garden

Did you know that a hose running for an hour can use the same amount of water that a family of four uses in a week? A trigger gun on the end of a hose makes it far easier to quickly turn water on and off, but using a watering can or collecting rainwater in a water butt and using that could be even better!

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