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What does it mean when a drought is declared?

Stonehenge is surrounded by yellow grasslandReuters

The grass surrounding the famous Stonehenge would usually look luscious and green but a lack of rainfall have left it parched

As we enter the fifth heatwave of the year this week, many areas across the UK have had low rainfall recently.

More than half of England and all of Wales has been declared to be in a drought.

Temperatures are likely to reach highs of 35-36C in parts of England on Thursday and and amber heat health alert has been issued for all of England except the North East where there is a yellow alert.

But what exactly is a drought? Keep reading to find out.

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A 'No Fishing' sign is pictured in the dried up Falmer Pond in Falmer, East Sussex, south of LondonGetty Images

This pond has dried up in East Sussex due to the prolonged hot weather

There isn't a single definition of a drought but the term is usually used to describe a long period of dry weather which has an impact on people, nature and the environment.

According to the Environment Agency some are short and intense while others are long and carry on over multiple seasons.

There are also different types of drought:

  • Agricultural drought - When there isn't enough rainfall to support crops and farming.

  • Environmental drought - When the lack of rainfall negatively impacts the environment and ecology.

  • Water supply drought - When companies have concerns about providing enough water to customers.

A combine harvester works on a dry fieldGetty Images

In England, the Environment Agency look at the amount of rainfall and public water supplies amongst other factors when deciding what sort of response is needed in a period of drought or water shortage.

There are four stages they look at:

  • Prolonged dry weather - Which begins to impact river flows, groundwater levels and water levels in lakes and reservoirs

  • Drought - The environment struggles with consequences for agriculture, people and businesses

  • Severe drought - When there are widespread and lasting effects on the environment, farming, people, communities, and the economy

  • Recovering from drought - When the impacts on the environment are reducing

Lwyn-on reservoir in the Taf Fawr valley has very low water levelsGetty Images

A drought has been declared across Wales. You can see how low the water levels are at Lwyn-on reservoir in the Taf Fawr valley.

Natural Resources Wales (NRW) has declared a drought across the whole of the country.

NRW said its teams were dealing with reports of "wide-reaching impacts to the environment" and that "conditions across Wales' natural environment have continued to deteriorate".

This includes drying riverbeds, fish in distress, an accumulation of algae, wildfire risk and concerns from farmers about crop growth, grazing conditions and water availability for livestock.

A man lies in the sun reading a book. He is lying in a field of dried yellow grass Getty Images

Do the grassy areas look like this near you?

Scotland works a bit differently. They monitor water scarcity instead.

According to the Scottish Environment Protection Agency (SEPA) water scarcity looks at when there is not enough water to meet the demands of humans and the environment.

Some Scottish rivers have reached "significant" water scarcity with the prolonged heat but Scotland has not been hit as hard as other parts of the UK.

Northern Ireland has not been experiencing the same conditions as Wales and England either and there are no official droughts declared.