![]() Where the rain ends up falling also matters. This is due to uncertainty around the influence of climate change on atmospheric circulation, such as the position and strength of the jet stream – a major driver of heatwaves and dry weather in the UK. PA Images/Alamy Stock PhotoĪlthough winters are projected to become wetter on average, scientists aren’t sure how the sequencing of dry seasons is changing. Holme Styes reservoir in Holmfirth West Yorkshire at the end of July. ![]() A drier than average winter is much more likely to be followed by a dry summer too. Research has shown that the probability of a dry winter and spring being followed by an extremely hot summer, like the one the UK is experiencing in 2022, is now at least five times more likely compared with the 1970s. The severity of future droughts will be determined by how sequences of dry seasons interact. Severe droughts in the UK’s past have always included one or more dry winters, such as 1975-76, 1988-12. Water demand will add an additional strain on these sources as the population grows, particularly as severe heatwaves are set to become much more common. ![]() There is less agreement between climate model simulations on how rainfall patterns will change in these seasons, which is when aquifers are usually replenished. How low rivers and public water supplies recede each summer will depend on rainfall in autumn and spring. Record rainfall in spring 2012 suddenly ended a drought which had begun in 2010, causing flash floods which affected more than 4,000 properties. There will be an increased risk of cascading hazards in future too, such as when a flood quickly follows a drought, spoiling crops and damaging infrastructure. Summer droughts are likely to affect the entire country, while multi-year droughts are more likely across southern England. Prolonged periods of below average river and groundwater levels are projected to become more severe. So what does that new climate look like? The latest set of simulations project hotter and drier summers plus warmer and wetter winters, with larger changes in summer compared to winter rainfall. The Environment Agency estimates that water demand may outstrip supply across southern England in as short a timescale as 20 years if the country does not adapt to its new climate by building reservoirs and desalination plants. The National Infrastructure Commission, which advises the government, warned then that the UK must do more to prepare for water shortages. The UK has experienced regular periods of drought in the past, including the last official drought in 2018-19. But with most of the UK forecast to have hotter and drier summers, it’s no longer as simple as that. A survey titled The Great British Rain Paradox conducted in 2020 showed that 77% of the British public agreed with this sentiment. Yet, the UK retains its reputation for being a rainy country. Projections by the UK Centre for Ecology and Hydrology suggest that flows will remain below average in these groundwater-fed rivers over autumn and potentially beyond. ![]() Rivers with underlying acquifiers in southern England (such as chalk streams) can take months to respond to changes in rainfall. ![]() The situation could significantly worsen if a dry autumn or winter follows. Reservoir levels were healthy entering 2022, having been replenished in the preceding autumn, but some in southwest England are now less than half full.Īt the time of writing, many rivers across southern England are exceptionally low. Short and intense rainfall, which does not replenish parched soils, rivers and aquifers as well as gentler, longer showers, is also increasingly common as warmer air can hold more moisture.Īlthough some water companies have enacted hosepipe bans to conserve water in the worst-affected areas, the Environment Agency has yet to declare an official water supply drought. Temperature trends, meanwhile, are more straightforward: increasing concentrations of greenhouse gases in the atmosphere have raised average temperatures and made dry periods in Britain drier, as hotter weather evaporates more water. This makes it very difficult to conclude trends from past observations. How the atmosphere circulates moisture is incredibly complex and so there is huge variability in rainfall from year to year. On top of that, southern England recently received just 17% of its average rainfall for July, in what was the country’s driest since 1935. The UK had the driest start to a year since the 1970s in 2022, with large parts of southern England receiving less than 50% of their normal winter rainfall. ![]()
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