Wednesday, 13 February 2013

BGS on Channel 4 flooding documentary

David Macdonald appeared in last night's Channel 4 documentary, "The Year that Britain Flooded".  As well as impressive footage of flood events, the programme explained some of the meteorological and hydrogeological processes which contributed to the flooding.

David used a water level dipper to measure the depth to water in one of our boreholes. The water level was close to the top of the borehole casing (metal tube), which sticks up above the ground level.

This borehole penetrates a confined aquifer: in this area, the Upper Greensand Formation is confined by overlying low permeability clayey chalk (chalk marl).  The water level is frequently above ground level, so the borehole was designed with the extra casing above ground level to allow us to measure the water level accurately over a greater range.  At times, including earlier this year, the water level rises even higher and water naturally flows out of the casing when the flange sealing the top is removed.
An image from inside the borehole casing showing David lowering the water level dipper down into the hole.

Wednesday, 23 January 2013

December 2012 overview

Groundwater levels - December 2012
We expect to see groundwater levels rising in December, as this is part of the usual recharge season when soils are wet and rainwater can infiltrate into aquifers.  However, the final month of 2012 was still exceptional - as the map shows, groundwater levels in over three quarters of our index wells exceeded their December average.

Record levels for December were seen in 7 index wells, e.g. Skirwith in the Sherwood Sandstone and Wetwang in the Chalk.  The second highest levels on record were seen at a number of sites including the long record boreholes Chilgrove House (since 1836) and Compton (1894) in the South Downs.  Further extensive groundwater flooding is probable given the high levels in the Chalk.

Groundwater flooding has been occurring in some Chalk areas, and groundwater discharge has been contributing to high flows in some streams and rivers for which the Environment Agency have issued flood alerts.

For more information, see the hydrological summary for December 2012 [PDF].

Wednesday, 9 January 2013

BGS hydrogeologists meet BBC's David Shukman

Screenshot from the BBC website of Andrew McKenzie's interview
A screenshot from the BBC website.
Yes, they've got our name wrong!  Survey, not Society!
It's been more of a wet Christmas than a white one!  The BBC have been interviewing BGS hydrogeologists to find out what impact recent rainfall has had on groundwater levels and the possibility of flooding.

Andrew McKenzie appeared in the lead item on the 6 O'Clock and 10 O'Clock news last week - you can view the clip on the BBC website.  That's our Wallingford office in the background.  We have a few boreholes on site that we use to monitor water levels.  They are also useful for testing equipment like pumps and downhole logging probes before we take them into the field.

Andrew was also interviewed on BBC Radio Berkshire's breakfast show on Monday.