Wednesday, 23 September 2015

August 2015 overview

Groundwater levels, August 2015
August was wetter than average for the UK (133% of the long-term average rainfall), bring a rather damp summer to a close (126% of average rainfall for the UK for June-August).  The south coast of England had particularly high rainfall in August, with over twice average rainfall falling over large areas, and nearly three times in some places.

The focus of the wet weather in August across southern England significantly reduced soil moisture deficits in this area, and caused temporary interruptions in seasonal recessions for some boreholes. 

The majority of the index boreholes were within or close to the normal range. In the Chalk, levels generally were near or below average, although Killyglen was above normal and Westdean No.3 was exceptionally high. Seasonal recessions were temporarily halted in localised areas of southern England (Ashton Farm, West Woodyates Manor, Tilshead and Houndean Bottom) by the late August rainfall, although the recessions may have since continued. 

Levels in the Jurassic limestones fell during August and were also normal or just below; recessions were again briefly halted.  In the Magnesian limestone, although levels generally were in the normal range, they fell at Swan House and rose slightly at Brick House Farm. In the slowly responding Permo-Triassic sandstones, with the exception of Llanfair DC, levels were near or above average, with record high August levels recorded at Newbridge (for the third month in succession) and also notably high levels at Nuttalls Farm (although lower than the exceptionally high levels in July). In the fast responding Carboniferous Limestone, levels fell but remained in the normal range in the Peak District, and rose in south Wales to be above normal, reflecting differences in regional rainfall.

For more information, see the Hydrological Summary for August 2015.

Hydrological Outlook from September 2015

The latest Hydrological Outlook is available.
Hydrological Outlook from September 2015

The forecast for precipitation over September-October-November as a whole is indistinguishable from climatology.

Groundwater levels in August exhibited a very similar pattern to recent months: below normal levels in parts of the southern and eastern Chalk contrasted with normal levels elsewhere in the aquifer. 

Levels in other aquifers were mostly normal, with above normal levels in some western aquifers, and variability in the Permo-Triassic boreholes where exceptionally high levels persist in Scotland. 

The one month outlook indicates a broadly similar pattern but suggests that levels in the southwestern chalk will return to normal. The three month outlook suggests this may be a shortlived effect, and a more mixed picture of normal to below-normal levels emerges across the southern Chalk. However, below normal levels in the north-east Chalk are likely to persist. Levels in other aquifers are likely to be normal or below-normal, with above-normal levels in parts of the Permo-Triassic sandstone.

For further information see the full Hydrological Outlook for September.