April 2018 felt like many seasons rolled into one month, encompassing freezing temperatures and snowfall, persistent wet weather and a settled spell with temperatures more typical of the summer. The rainfall pattern, above average for the UK as a whole, but below average in northern Scotland and parts of Northern Ireland, reinforced that of March. With a wet start to spring, river flows were notably high in much of England and Wales, and normal or above normal elsewhere.

There was a short, sharp spell of unseasonably high temperatures, including the warmest April day since 1949 (29.1°C at St. James' Park, London) and Soil Moisture Deficits (SMDs) began to develop, although soils remained wetter than average in England.

The assessment is contained in the latest monthly hydrological summary for the UK, an authoritative analysis of the country's water resources status. The monthly summaries are produced by the National Hydrological Monitoring Programme, operated by the Centre for Ecology & Hydrology (CEH) in conjunction with the British Geological Survey.

Substantial late groundwater recovery has offset the delayed start to the recharge season last winter and levels were in the normal range or higher, and exceptionally high for April in most aquifers in north-east and south-west England, although the risk of groundwater flooding is low. Summary author Cath Sefton said, "With the recharge season drawing to a close, and reservoir stocks close to average for the time of year, the water resources outlook for summer 2018 is healthy."

Map showing river flows in UK hydrological summary of April 2018

Read the full April 2018 UK Hydrological Summary here.

The monthly summary is a look back at hydrological events occurring in March 2018. Latest information on flood warnings is provided by the Environment Agency, Natural Resources Wales and Scottish Environment Protection Agency (flood warnings for Northern Ireland are not available).

The Centre for Ecology & Hydrology jointly operates the National Hydrological Monitoring Programme (for the UK) in conjunction with the British Geological Survey. NHMP scientists produce the UK Monthly Hydrological Summary which assesses rainfall, river flows, groundwater and reservoir levels. They also operate the UK’s National River Flow Archive.

The NHMP also has a remit to analyse major flood and drought events in the UK and analyse long-term trends in UK hydrological data. The UK Monthly Hydrological Summary is normally published on, or before, the tenth working day, of the following month. A Hydrological Outlook for the UK is also available, and is updated monthly. The latest Outlook can be viewed here.

Additional information

April 2018 UK Hydrological Summary

National River Flow Archive

National Hydrological Monitoring Programme

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