Tuesday, 19 January 2016

December 2015 overview


Groundwater levels, Dec 2015
Groundwater levels, December 2015
The UK saw widespread and severe fluvial flooding in December, as exceptional rainfall led to some very high river flows.

Levels in the index boreholes were generally in the normal range or above for December. Levels recovered in response to winter recharge, except at some sites in parts of the eastern Chalk with thick unsaturated zones or where recharge was limited by superficial deposits (Aylesby, Therfield Rectory, Stonor Park, Well House Inn and Westdean No. 3)
and at Nuttalls Farm (in the Permo-Triassic sandstone).

Groundwater level hydrograph for Newbridge
Groundwater level at Newbridge, near Dumfries
The exceptional rainfall in the northern half of the UK resulted in high groundwater levels with record monthly values recorded at Killyglen (Chalk) and Newbridge (Permo‑Triassic sandstone). The groundwater level for Newbridge, near Dumfries, was the highest December value since records began in 1993.

Other levels in the north were notably high, except for Dalton Holme, which normally
responds slowly to recharge from rainfall. Groundwater from the Corallian aquifers at Old Malton in North Yorkshire contributed to high river levels, and high groundwater levels in permeable superficial deposits contributed to flooding in river valleys across northern Britain.

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

Wednesday, 13 January 2016

Hydrological Outlook from January 2016

The latest Hydrological Outlook is available.
Hydrological Outlook from January 2016


December groundwater levels in the Chalk displayed a very mixed pattern, with below normal levels in some boreholes in central southern England and normal or above normal levels elsewhere. 

In other aquifers levels were normal or above normal, with very high levels in some northern aquifers.  For example, the groundwater level at Newbridge near Dumfries is exceptionally high (see hydrograph below).

Based on early January rainfall, groundwater levels in the next month are likely to be normal or above except in the slower responding parts of the Chalk in central and eastern England.
Hydrograph from Newbridge, showing
groundwater levels in Permo-Triassic Sandstone

Exceptionally high levels will persist across Permo-Triassic aquifers in the north. In the Yorkshire Chalk and in Wessex and along the south coast, levels may rise to notable or exceptional levels and this may result in localised groundwater flooding.

The three month outlook suggests a similar pattern, with normal to above normal groundwater levels prevailing, and a significant chance of notably high or exceptionally high levels in the most responsive aquifers.

For further information see the full Hydrological Outlook for January.

Thursday, 7 January 2016

Groundwater and the recent floods

The flooding that has occurred in Northern England and Scotland in the past month has primarily involved surface water, so we didn't think there would be a great interest in our thoughts on it.  However, the web logs for the BGS website showed that many people had been searching for information on the floods.  Yesterday we put up a web page which answers the question:
 Has groundwater influenced the recent UK floods (December 2015 — January 2016)?

If you've got any questions then we'll be happy to try and answer them.  Join the conversation on our Twitter feed: @BGSGroundwater

Wednesday, 18 November 2015

October 2015 overview

End of October soil moisture deficits were lower than average in the south of England
Groundwater levels, October 2015
reflecting the late summer 
rainfall, but above average in central and eastern England.  

Groundwater levels remained stable or continued their seasonal recession in the majority of index boreholes.

However, in the Chalk of south Dorset and the western South Downs levels at Ashton Farm, Compton House, West Woodyates Manor and Chilgrove House continued to rise (the last two by three metres) in response to recent recharge. Levels at Compton House and Chilgrove House rose to the normal range, whilst levels at Ashton Farm remained notably high. Elsewhere, levels fell in October and were generally average or slightly below at month-end, with the exception of Tilshead, Well House Inn, Dalton Holme and Wetwang which were notably low and Little Bucket Farm which rose to above normal. 

In the Jurassic and Magnesian limestones, levels fell or stabilised and were in the normal range. In the slower responding Permo-Triassic sandstones levels fell, returning to the normal range after four months of record high levels at Newbridge. Levels were average or above, with the exception of Llanfair DC which is notably low.

Levels in the rapidly responding Carboniferous Limestone boreholes of south Wales and the Peak District fell and were all below normal. Levels at Greenfield Garage fell from notably high at the end of September to below normal. 

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

Hydrological Outlook from November 2015

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


In the Chalk, levels in October were mostly normal or below. Notably low levels persisted in north-east England, while southern England saw a mixed pattern with some notably low levels in more central areas contrasting with above normal levels in parts of the far south. Levels in other aquifers were also mostly normal or below. 

The one month outlook indicates a similar pattern. For the three month outlook, below-normal levels are far less prevalent, with normal levels predominant across all aquifers and above normal levels possible in some localised areas. The shift towards normal levels again reflects the precipitation forecasts but, as with river flows, projections are highly uncertain.

Groundwater projections are particularly uncertain at this transitional time of year; late autumn and early winter rainfall will be highly influential on the longer-term outlook.

Thursday, 15 October 2015

September 2015 overview

Groundwater levels, September 2015
September was a dry month, with less than half of the long-term average rainfall.  The west of Scotland was particularly dry, but only south eastern England had close to or slightly above average rainfall.

Soil moisture deficits remained similar to those at the end of August for most regions in England and Wales, but were closer to average. Consequently, the majority of the index boreholes continued their seasonal recessions in September.

In the Chalk, levels were average or below, except at Ashton Farm where they were notably high following an increase in September. Increases were also observed at West Woodyates Manor, Compton House and Chilgrove House (all in Dorset or the western South Downs). 

Levels in the Jurassic limestones were similar to, or below, those recorded recorded at the end of August. In the Magnesian Limestone, levels fell but remained in the normal range. 


Groundwater levels at Alstonefield (Carboniferous Limestone)
In the slower responding Permo Triassic sandstones, levels fell at all of the index boreholes. With the exceptions of Llanfair DC and Skirwith, levels were normal or above.  A new period of record month-end maximum level was recorded at Newbridge (for the fourth consecutive month) and levels remained notably high at Nuttalls Farm. 

In the fast responding Carboniferous Limestone, levels fell and remained in the normal range at Alstonefield. In south Wales, levels rose at Greenfield Garage and fell at Pant y Lladron, but levels remained above normal in both boreholes.




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

Hydrological Outlook from October 2015

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


Following a dry September, the probability that UK precipitation for October-November-December will fall into the driest of five equal categories is 15% and the probability that it will fall into the wettest of five equal categories is 35%.

Across the chalk aquifer, levels in September were below normal in central southern England and in much of eastern England, and normal elsewhere. 

Levels in other aquifers were mixed, mostly normal to below except for above normal levels in parts of the Permo-Triassic sandstone and Carboniferous limestone. 

Groundwater levels are expected to be normal to below normal over the next month, but with above normal levels occurring in parts of the southern Chalk, mainly in response to the August rainfall. Over the next three months, normal levels predominate, but the outlook is much more uncertain as this is the period where winter recharge typically starts; entering the recharge season with broadly normal groundwater levels, the outlook is highly sensitive to late autumn rainfall.

For further information see the full Hydrological Outlook for October.