The science of drought explained in pictures

  • In Science
  • 2022-08-12 11:53:36Z
  • By BBC
Parched cricket field
Parched cricket field  

From all the pictures of parched fields, dusty soil and dried-up reservoirs, it might appear obvious there's a drought.

But from a scientific point of view, it's more complicated than that.

There's no one definition of drought - it's different depending on whether you look at weather, agriculture or water flow in rivers and streams.

And when it comes to declaring an "official" drought, government agencies look at how the long dry spell is affecting food production, water supplies and the environment.

That includes how much rivers and streams are shrinking, which puts wildlife and water supplies at risk. They also look at threats to crops and livestock if fields are turned into dust bowls.

How water supply is affected

One big indicator for drought is hydrology - the flow of water through rivers and the state of the water stored underground in permeable rocks beneath the soil.

Baitings Reservoir in West Yorkshire
Baitings Reservoir in West Yorkshire  

These are crucial for supplying the drinking water that reaches our taps.

Rivers are running at exceptionally low levels in much of southern England and Wales, including the River Yscir, Colne and Wye. There are reports of streams drying up and rivers shifting downstream.

River Thames at Kemble
River Thames at Kemble  

The amount of water stored in aquifers - the layer of spongy rock that soaks up water - is below normal for this time of the year.

Reservoirs are also running empty. At the end of July reservoirs were at their lowest levels in England and Wales since records began in 1990, according to the UK Centre for Ecology and Hydrology.

Depleted reservoir
Depleted reservoir  

A north-south divide

But it should be noted that there's something of a north-south divide. Because of the UK's geological make-up and the influence of weather patterns, some parts of northern England and Scotland are escaping the worst of the parched conditions.

Rivers in the north are generally at higher levels and also respond much more quickly when rain falls.

That said, the drought in much of southern England and parts of Wales is likely to persist for some time. Even if it does rain, it'll take a long time for river levels to fill up enough to return to normal flows.

How drought affects food and wildlife

Experts warn the extreme weather will likely lead to smaller harvests, which will make the food we buy in the supermarkets even more expensive.

Field of damaged maize
Field of damaged maize  

Scientists will be monitoring the impacts of the drought on wildlife. As water courses dry up or run low, habitats for fish and invertebrates start to shrink, with knock-on effects for animals higher up the food chain.

And pollutants in rivers become more concentrated, amplifying their impact on wildlife.

How climate is linked to drought

Experts will also be looking at the wider question of the links between heatwaves, drought and climate change.

The UK has experienced regular periods of drought in the past, including the last official drought in 2018-19. And to a certain extent, drought is normal and part of natural weather cycles across the world.

But dry conditions are also expected to become more frequent and intense as Earth moves beyond the 1.2°C of climate change we have seen to date.

The ten warmest years on record in the UK have occurred in the 21st century, with data stretching back to 1884.

Top 10 hottest UK days on record
Top 10 hottest UK days on record  

Climate scientists say that the UK's extreme heat in July would have been "almost impossible" without human-induced climate change.

July was the driest in England since 1935, with many areas seeing far less rainfall than average.

Weekly rainfall
Weekly rainfall  

The latest set of simulations for the UK project hotter and drier summers, plus warmer and wetter winters, with larger changes in summer compared to winter rainfall.

That means water companies and farmers will have to plan how to harvest and store rain in winter to address shortages in the summer.

Follow Helen on Twitter @hbriggs.


More Related News

China protests: Why is it struggling to vaccinate the elderly?
China protests: Why is it struggling to vaccinate the elderly?

China has not vaccinated enough old people, making it difficult to abandon its zero-Covid policy.

Putin's war in Ukraine looks more and more like a failure. Past Russian leaders haven't survived similar mistakes.

For now, Putin's rule appears secure, but the experiences of past Russian leaders show how failure at the front can lead to downfall at home.

Five ways to spend and waste less this Christmas
Five ways to spend and waste less this Christmas

Experts give tips on how to make your Christmas cheaper, greener and just as joyful.

7 photos that show the climate crisis is not a distant threat - it
7 photos that show the climate crisis is not a distant threat - it's already here

Images of raging wildfires, damaging storms, flashing floods, and extreme drought showcase a planet that's been transformed by climate change.

Notpla: UK plastic-alternative developer among £1m Earthshot Prize winners
Notpla: UK plastic-alternative developer among £1m Earthshot Prize winners

A London firm which developers nature-friendly packaging is among five climate prize winners.

Leave a Comment

Your email address will not be published. Required fields are marked with *

Cancel reply


  • -Buy Self Defense ammunition Glock guns USA & Canada

    -Buy Glock 17 Gen5 9mm - Pistol Glock 19 Gen5 for sale

    -Buy Handguns,Pistols,Body Armor, Ak-47 & Ak-74, Tactical Rifles,

    -Buy Firearms Dealers, Buy Firearms Shop Online

    -Glock Guns for Sale Online Australia

    The most important properties at a glance:

    • High precision
    • Tenifer coating
    • Simplest construction
    • Impact-resistant plastic
    • Improves precision
    • Safe Action trigger system
    • 3 automatic backups

    With a devoted group, our attention on guns and ammunition permit us to purchase the best quality in huge amounts and pass the investment funds to you.

    We provide 24/7 support to our customers. We offer free shipping for orders above $2000

    We offer instant refund for orders purchased within a week. When you receive your order and you are not satisfied, we will issue a refund.

    Skype: live:.cid.930eaa60e0bc59b0


Top News: Science