Tilshead Borehole Levels: 12th November 2023

We’ve been monitoring the water levels in the Tilshead borehole during winter over the last decade, and it has proved to be an excellent indicator of when the village might be prone to groundwater flooding, hydrostatic flooding and flooding from the River Till.  Monitoring doesn’t start in earnest until 1st December as it is rare for the groundwater to build up until then.  However, in some years, like 2020 and this year, autumn storms bring a lot of rain very early in the season, so an intermittent watch is kept on water levels.  As the question of where things are has already been asked, it is probably useful to put things into context.

The red dots show how the water level in the aquifer has risen rapidly over the first 12 days of November 2023 (and NOT December as shown on the graph).  That is some 6 weeks ahead of the rapid flood rise in the winter of 2013-2014 and that in 2019-2020 when the level on 1st December 2019 was already over 90 metres above the ordnance datum (AOD).  The next chart shows the levels today compared to the levels on each 1st December over the last decade.

So, we are only 2 metres away from the position we were in in December 2019 and around 10 metres above the level we might expect in early December.  What happens next?  Clearly, much more heavy rainfall and we could be into flood alert territory well before the end of the month.  However, warm weather, with growing grass and leaves staying on the trees for a little longer might slow things down a little.  Those living in properties prone to groundwater and hydrostatic flooding would be well-advised to check on their flood mitigation measures earlier rather than later this year.

More heavy rain is forecast for tomorrow as Storm Debi hits, with unsettled weather and an increasing chance of rain towards the end of the week.  Apart from a brief period of high pressure at the end of next week, similar unsettled weather is likely to keep the country in its grip until early December.



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Winterbourne Stoke Parish Council