Hydrological Summary for May 2021 published

Whilst temperatures remained below average, the high rainfall in May marked a sharp transition from an arid April. Recovery to warmer weather was delayed until the last week of May, making it the coldest April-May period in England since 1951. The total May rainfall for the UK was 177% of average, and Wales saw its wettest May in a series from 1910. River flows were above average across much of the UK, exceptionally so in Wales, where the mean May outflow was the highest in a series from 1961. Despite the high May rainfall and accompanying reduction in soil moisture deficits (SMDs; which by month-end were below average except in Southern region), groundwater levels in the index boreholes continued to recede (with the exception of some in the west). Generally, reservoir stocks were close to average, with notable recoveries in Yorkshire (Washburn and Bradford Supply) and south-west England (Clatworthy and Wimbleball), whilst at Loch Thom and Teesdale below-average stocks persisted. With near-average groundwater levels in the south and east, and reservoir stocks healthy across England, Wales and Northern Ireland, the water resources situation is generally favourable entering the summer. June started with a dry spell, but only in western Scotland does this add to longer-term deficiencies.

Read the Hydrological Summary