Wednesday, 17 February 2016

January 2016 overview

Groundwater levels, January 2016
January was very wet (the 4th wettest January since 1910), with all regions registering above average rainfall.  Over double the average rainfall was recorded in north-eastern areas and along the south coast.

The saturated soils throughout the UK meant groundwater levels responded to recharge in all aquifers. Levels were in the normal range or above, apart from two slowly responding sites in the Chalk of central and eastern England. At fast responding sites, the rapid rise in levels that commenced in December continued into January. 

Levels in many aquifers fell mid-month, but generally rose again by month-end (e.g. in the Chalk of the South Downs, parts of the Cotswolds limestones, most of the Permo-Triassic sandstones and the Carboniferous Limestone of south Wales). At month-end, water levels in the Chalk were notably or exceptionally high (at Wetwang and along the south coast) where levels responded rapidly to the exceptional rainfall, or in the normal range and rising at slowly responding sites. However, groundwater flooding in the south-east of England was localised and minor, with a few flooded cellars and surcharged sewers.
Hydrograph from Chilgrove, showing
groundwater levels in the unconfined Chalk

The hydrograph from Chilgrove (West Sussex) in the unconfined Chalk aquifer of the South Downs shows a groundwater level of about 74 mAOD at the end of January, some 17 m above the average level for that time of year.  The multiple peaks are typical of this observation well: levels rise after periods of prolonged of heavy rainfall but decline during drier periods. This is typical of a responsive part of the Chalk aquifer.

Groundwater level at Newbridge, near Dumfries,
in the Permo-Triassic sandstone
Levels in the Permo-Triassic sandstones were generally in the normal range, with the exception of north-west England and south-west Scotland where they were higher due to the exceptional rainfall over the last three months; a record monthly level was again recorded at Newbridge.

Levels rose in the Magnesian Limestone index boreholes, with a record maximum January level recorded at Brick House Farm.

For more information, see the Hydrological Summary for January 2016.

Hydrological Outlook from February 2016

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

The rainfall received during December and January brought groundwater levels into, or above, their normal range across most aquifers.

Groundwater levels in the rapidly responding Chalk aquifers along the south coast rose quickly, and are likely to stay notably high over the next one to three months.  

In other parts of the Chalk levels will generally be normal or above normal; where they are currently below normal in some aquifers in central and eastern England the trend is for rising levels. In Yorkshire drier conditions in January have slowed the rate of increase seen since December, but levels should remain above normal over the next three months. 

The Permo-Triassic sandstone aquifers in northern Britain characteristically respond slowly, and this means that the exceptionally high levels recorded in these aquifers will be likely to persist over the next three to six months.

For further information see the full Hydrological Outlook for February.

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.