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.

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