Q&A: England drought

Parts of England continue to be in a state of drought because of extremely low rainfall over two successive winters, prompting hosepipe bans in some areas.

What does this mean and why has it happened?

What is a drought?

Droughts are natural events which occur when a period of low rainfall creates a shortage of water.

The conditions are often thought to be associated with a short spell of hot, dry weather, but can actually take some time to develop.

Dry winters can have a particularly big impact on water resources because, under normal conditions, winter rain tops up groundwater and reservoir levels while summer rain helps to maintain reservoir levels and keep rivers flowing.

Which areas are currently affected by it?

With the most recent additions of the South West and the Midlands, regions covering much of England are officially classified as in drought by the Environment Agency after two dry winters "left rivers and ground waters depleted".

Hosepipe bans have been put in place across much of England because homes and businesses rely on water pumped from rivers and the ground.

Seven water companies across south and eastern England, which serve about 20 million people between them, have imposed such bans.

Anglian Water says its regions have had their driest 18 months for a century.

Thames Water says that, since records began in 1884, only 1892/93 and 1920/1921 have seen less rainfall than in the past two years.

Are there different types of drought?

Yes. One form, known as an environmental drought, occurs when water levels in rivers are too low and there is insufficient moisture within soil. High levels of soil moisture are needed to replenish underground water stores.

This type of drought was declared by the Environment Agency in the Anglian region in the summer of 2011. Since then environmental drought has been declared in most of England south of Sheffield.

Water company droughts are declared when levels in reservoirs are particularly low.

Is a certain type of rainfall needed?

Yes. Long periods of persistent very light rain are needed because more water is absorbed by the earth than is the case with heavy rain.

Summer rain tends to fall in the form of heavy thunderstorms, and is then soaked up by plants or runs off the ground. As a result, heavy rainfall is not what is needed.

Winter tends to be characterised by drizzle, which is when groundwater is usually recharged for the following year. The lack of this type of rain in recent winters led to the drought being experienced in parts of the UK.

Source: Defra

How much longer is the current drought likely to last?

There are fears that there could be a third successive dry winter.

Seasonal forecasts remain in their infancy, but there are concerns based on the expectation that the rain likely in the summer - ie thunderstorms - is not the type that would be absorbed by soil.

Why are some areas affected more than others?

An array of factors - which include rainfall, housing, air pressure and reservoir infrastructure - all combine to determine which areas are more susceptible to drought.

South-eastern England has been hit particularly hard in recent years because of its high population density, relatively low number of reservoirs and a heavy reliance on groundwater supplies.

Groundwater provides about 75% of public water supply in south-east England, compared with a figure of 30% across England and Wales as a whole.

The South East's population is growing constantly and the demand for water grows daily. Conversely, as the population grows, the demand for new houses grows and these houses are often built on flood plains, leaving the region susceptible to flooding.

In addition to such patterns of human behaviour, the prevailing weather pattern in recent years has seen low pressure move up past the west coast of Ireland and into Scotland bringing rain with it. Further east, less rain reaches south-east England.

What can be done to end the drought and prevent others?

A return to the standpipes of the 1976 crisis is unlikely.

As a last resort, water companies could seek an emergency drought order which could include cutting off supplies to homes on a rota basis and standpipes.

In reality, water companies will do everything they can to avoid this situation, and stricter restrictions than ever before mean standpipes are unlikely.

Where longer-term planning is concerned, water companies are investing in mains replacement programmes in a bid to reduce leakage. Industry regulator Ofwat monitors water companies that fail to meet their targets, working with them to help reduce leakage.

Individuals can make an effort to use available water resources more efficiently in order to reduce the demand on the environment.

The Directgov website includes water-saving tips such as: