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New monthly Hydrological summary published, for July 2011 – Rainfall appreciably above average in many regions
12 August 2011
Rainfall totals for the UK were appreciably above average during the month of July. All regions reported at least 90% of the 1971-2000 average and rainfall deficiencies across most of southern Britain have moderated. However, spatial variations in rainfall within some regions were considerable with below average totals reinforcing meteorological drought conditions in parts of central England.
The above analysis is contained within the latest monthly hydrological summary (for July 2011) produced by the National Hydrological Monitoring Programme, operated by the Centre for Ecology & Hydrology in conjunction with the British Geological Survey.
High rainfall totals led to many northern rivers being in spate with flood alerts common in mid-month. Correspondingly, overall reservoir stocks declined by less than normal through July and stocks in index reservoirs across much of northern Britain remain above the late-summer average. However, stocks are seasonally low in Rutland Water, the Derwent Valley reservoirs, and in a number of reservoirs in the South West; early-August stocks for Wimbleball were the lowest since 1992.
Relative to the monthly average, river runoff rates are significantly healthier than in the late spring but depressed flows continue to characterise rivers in parts of central and southern England. After almost six months with very meagre infiltration, the hydrological impact of the drought is now clearly evident in the low, to very low, groundwater levels across most of the major aquifer outcrop areas.
Jamie Hannaford from the Centre for Ecology & Hydrology said, “With end-of-July soil moisture deficits remaining close to record maxima in parts of central England a substantial delay in the seasonal recovery in runoff and recharge rates may be expected. The autumn rainfall will be very influential in determining whether drought stress will extend into 2012.”
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.
Read the full July 2011 Hydrological Summary for the UK [PDF, 2.40mb]
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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