Within the UK February 2011 was notably mild with most areas registering above average rainfall – primarily the result of active Atlantic frontal systems which brought gales to many western areas. Most rivers were in spate during the first ten days of the month; flood alerts and, generally moderate, floodplain inundations were common. However, the winter (December to February) precipitation total for the UK was considerably below average (for the third successive year) with notable deficiencies in some western and northern areas.
The above analysis is contained within the latest monthly hydrological summary (for February 2011) produced by the National Hydrological Monitoring Programme, operated by the Centre for Ecology & Hydrology in conjunction with the British Geological Survey.
The above average February rainfall and near-saturated soil conditions made for plentiful replenishment to reservoirs, and most aquifers, across the majority of the country. Although some modest drawdowns were required to moderate flood risk, reservoir stocks generally increased appreciably. Overall stocks for England &Wales rose to a little above the early-March average and stocks in the majority of upland index reservoirs were within 5% of capacity. In southern Britain, mostly in the South West, a few reservoirs remain below average but well above late-winter minima.
After a belated seasonal recovery, groundwater levels are within the normal range across most outcrop areas but still considerably below the early spring average in parts of the southern Chalk and in some wells in the Midlands. In those areas with significant long term rainfall deficiencies weather patterns in the early spring will be particularly influential in determining the water resources outlook.
The Centre for Ecology & Hydrology jointly operates the National Hydrological Monitoring Programme (NHMP) 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 National River Flow archive. The NHMP has a remit to analyse major flood and drought events in the UK and analyse long term trends in UK hydrological data. The Programme was set up in 1988 and relies on the active co-operation of measuring authorities throughout the UK.
Notable statistics for February 2011
- Sustained frontal rainfall (often with orographic enhancement) resulted in some notable 24-hour rainfall totals during February 2011. For example Capel Curig in Snowdonia reported 121.6mm on the 5/6th February
- Many rivers in central southern and south-west England reported below average runoff during February 2011; the Taw and Tone (Somerset) both recording only a little above 50% of the February average. For the River Tone, the March to February (12 month) runoff total is the 3rd lowest in a 50-yr record
- On the 5th February 2011, the Conwy and upper Dee registered their highest February flows in records of 47- and 41-years respectively
- Provisionally, the Wessex Region registered its 3rd lowest March-February (12 month) rainfall since 1975/76; much of the Severn-Trent Region was also particularly dry in this timeframe
- Despite the wet February, most regional rainfall totals for the winter were appreciably below average, notably so in the Western and Northern Isles where deficiencies exceeded 30%.
Related CEH links
Read the full February 2011 Hydrological Summary for the UK [PDF, 2.0mb]
Details of the National Hydrological Monitoring Programme
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.
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