Stonor Park

The Stonor Park well, measuring levels in the Chalk aquifer near Henley on Thames. Its hydrogeological setting, and the absence of major abstractions in its vicinity, mean it is often cited as a 'typical' chalk observation well.

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Hydrograph

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Information about the well

Stonor Park
Wellmaster ID	SU78/45A
NGR	4741 1892
Datum	121.29 m AOD
Monitoring details
Type	Groundwater Level
Aquifer	Chalk
Confinement	Unconfined
Depth	87.5 m
Record
Monitored by	EA Thames
Records commence	1961
Records end	Active

Hydrogeological setting

The borehole monitors water level in the Berkshire Downs Chalk above Henley on Thames. It is drilled into the Lewes Nodular Chalk. The aquifer is unconfined.

Geological map of the area around Stonor Park (click for key)

Well or borehole construction

The well consists of a 2.2 metre diameter shaft to 60 metres and a 152 mm diameter borehole to 87.5 metres.

Hydrograph response

This hydrograph has a very regular annual sinusoidal pattern, capturing the aquifer's full range of fluctuation, although analysis suggests that there may be a constraint on low levels. As levels don't reach the bottom of the well, the constraint may be hydrogeological.

The relative simplicity of the borehole's response to recharge has meant that it is frequently cited as a typical Chalk well, and used in modelling exercises to link precipitation, recharge and water level. The Chalk block monitored by Stonor is, in fact, slightly atypical in that it is one of the larger blocks without surface drainage, and responses to individual recharge events are damped.

Flow in the Assendon spring is initiated when water levels reach 85.5 metres aod, which tends to occur around once per decade.

Data issues

Uninterrupted weekly data from 1963.

References

A preliminary risk assessment of the potential for groundwater flooding during the winter of 2007/8 — an update.

Topographic map with hillshade of the area around Stonor Park

Acknowledgements

At a national level, groundwater level monitoring data is collected and managed by the Environment Agency (England), the Scottish Environmental Protection Agency, Natural Resources Wales and the Department of the Environment (Northern Ireland). Access to the data they collect (which includes many monitoring sites beyond those highlighted on these pages) and curate is online in England (DEFRA) and Scotland (SEPA).