After a dry March in many parts of the UK, April was a notably cool month with rainfall close to the long-term average on the national scale, according the Centre for Ecology and Hydrology. CEH said precipitation patterns varied across the UK with some regions experiencing another consecutive month of below-average rainfall.

Some areas have seen "appreciable deficits" in rainfall over the first four months of 2013. Parts of Cheshire and North Wales experienced very little rain in April. For areas of the North-West, the January-April rainfall total is estimated to have been the second lowest since 1964.

Across Central and Eastern England, soil moisture deficits have exceeded the end-of-April average, meaning that unless May is wetter than usual, the 2012/13 recharge season could come to a close across significant areas.  

The hydrological summary for the UK, released on Thursday, showed that, despite the observed shortfalls in some areas, the overall picture for the UK is healthy; CEH reported that, "despite the relative dryness of the early months of 2013, 12-month rainfall accumulations remain above average in almost all regions." The Hydrological Summary assesses rainfall, river flows, groundwater and reservoir levels.

Terry Marsh from the Centre for Ecology & Hydrology commented, "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 percent 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.

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