Wednesday, 20 May 2015

April 2015 overview

Groundwater levels, April 2015
With little rainfall and some very warm weather, soil moisture deficits (SMDs) climbed steeply through April and, by month end, were substantially above average across the main aquifer areas (SMDs were double the typical end-of-April magnitude across the Chalk outcrop).

Consequently, levels fell at index wells throughout the country, with a few exceptions: the slowly-responding Chalk at Therfield Rectory and Dial Farm in eastern England, the Permo-Triassic sandstones at Nuttalls Farm and the Carboniferous Limestone at Alstonfield in the Midlands.

In the Chalk, levels were generally still within the normal range but below average for the time of year in Yorkshire, Northern Ireland and Dorset-Wiltshire, whilst they remained above average in the eastern part of the North Downs and upper Lee valley of Hertfordshire. However, compared with the exceptionally high groundwater levels in the Chalk in April 2014, when groundwater flooding was still present in some areas, they are now up to 4 m lower across southern England (and over 6 m and 12 m lower at Therfield Rectory and Stonor Park, respectively).
Groundwater level hydrograph, Stonor Park (unconfined  Berkshire Downs Chalk)
In the fast responding Jurassic and Magnesian limestones, levels remained average or below and in the slow responding Permo-Triassic sandstones they were average or above (still exceptionally high at Newbridge, an area receiving above‑average autumn and winter rainfall, and Nuttalls Farm). Groundwater levels in the Lower Greensand of south-east England remained above average. With the modest rise in level at Alstonfield, Carboniferous Limestone levels were in the normal range in both Derbyshire and south Wales.

As little recharge is anticipated from now until the autumn, the current picture is likely to persist unless substantial late spring or summer rainfall is received.

For more information, see the Hydrological Summary for April 2015 [PDF].

No comments:

Post a Comment

Thanks for adding a comment.