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UK Hydrological summary for January 2012 published: North West-South East rainfall gradient

Tue, 02/14/2012 - 1:10pm

14 February 2012

Gladhouse Reservoir, Midlothian

Gladhouse reservoir, Midlothian

The synoptic patterns which have produced a remarkably sustained exaggeration in the NW-SE rainfall gradient across the UK continued in January 2012. Much of central, eastern and southern England was again relatively dry and the development of the current regional drought now extends across three winter periods with a range of impacts embracing water resources, agriculture and the aquatic environment.

The above analysis is contained within the latest monthly hydrological summary (for January 2012) produced by the National Hydrological Monitoring Programme, operated by the Centre for Ecology & Hydrology in conjunction with the British Geological Survey.

Reservoirs were near to capacity in early February across Scotland, Northern Ireland and most of Wales. Stocks have held up well in a number of large pumped-storage impoundments in the drought-affected regions (Farmoor was virtually full entering February) but are seasonally depressed in a number of smaller reservoirs (including farm reservoirs and those supplying canals). Early February stocks were substantially below the previous minimum for Ardingly (West Sussex) and the 2nd lowest in a series from 1998 at Bewl (East Sussex).

Flood alerts were common in Scotland during early January but river flows in many central and southern rivers have been notably depressed since the early autumn and the meagre January runoff was accompanied by a further contraction in the stream network.

Very limited aquifer recharge since 2009 has left groundwater levels close to period-of-record minima in some parts of the English Lowlands. Measures to moderate the drought’s impact are being widely deployed (from groundwater augmentation of low flows to appeals for reduced water usage – contingencies normally associated with an arid summer rather than the late winter). The window of opportunity for further substantial aquifer recharge (before evaporative demands rob the rainfall of much of its hydrological effectiveness) is narrowing rapidly.

Terry Marsh, Centre for Ecology & Hydrology said, "Much of central, eastern and southern England was again relatively dry in January 2012 and the development of the current regional drought now extends across three winter periods with a range of impacts embracing water resources, agriculture and the aquatic environment. In the absence of an unusually wet late winter and early spring (as happened in 2000 and 2001 for example), it is now virtually inevitable that a significant degree of drought stress will be experienced in 2012.  The magnitude of that stress, and its spatial extent, will be heavily influenced by rainfall over the next eight to ten weeks."

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.

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