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April was a notably cool month with rainfall close to the long-term average at the national scale – but spatial variations in precipitation totals were large and appreciable deficits have become established in some regions over the first four months of 2013, according to the latest update to the UK's most authoritative analysis of water resources status.

River flows - January 2013 to April 2013

Notwithstanding the low temperatures, evaporation losses have remained within the normal range and soil moisture deficits exceeded the end-of-April average across many eastern and central areas of the country. In the absence of above average May rainfall, this could signal the termination of the 2012/13 recharge season across much of the outcrop areas of the major aquifers.

The analysis is contained in the monthly hydrological summary for the UK, covering the month of March 2013. 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.

Terry Marsh from the Centre for Ecology & Hydrology said, “Groundwater levels are still above average in most areas (with a continuing possibility of landslide activity in vulnerable areas and a diminishing risk of groundwater flooding) and the water resources outlook is healthy. Rainfall over the next 4-6 weeks will be particularly influential in determining river flows and the status of groundwater resources through the summer.”

The latest summary also showed that reservoir stocks were healthy entering May, exceeding 90% of capacity at the great majority of index reservoirs across the country.

April runoff totals were also generally well within the normal late-spring range, but river flow patterns varied markedly across the country, with significant flooding in Scotland around mid-month and seasonally depressed runoff around month-end in a number of rivers draining impermeable catchments to the south.

A PDF of the full 12-page April 2013 summary can be downloaded here. [PDF 1.8MB]

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 published on, or before, the tenth working day, of the following month.

Additional information

Read the full April 2013 Hydrological Summary for the UK [PDF, 4.9mb]

Hydrological summary archive - dating back to December 1988

Details of the National Hydrological Monitoring Programme

Datasets hosted by CEH: National River Flow Archive, National Water Archive and others

Media enquiries related to the Hydrological Summaries should be directed to the CEH Press Office. Our scientists can provide explanation and analysis of historic hydrological patterns, possible future scenarios under climate change and scientific understanding of the current situation. We are not able to comment on immediate operational issues.

If you wish to reproduce figures from the Monthly Hydrological Summary please respect the copyright credits contained within the document.