Llanfair DC

The Llanfair DC borehole measures groundwater levels in Permo-Triassic Sandstones in the Vale of Clywd.

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Hydrograph


Hydrograph

Show data from :-
1972 to 2013 1970s 1980s 1990s 2000s 2010s


Information about the well

Llanfair DC
Wellmaster ID SJ15/13
NGR 3137 3555
Datum 83.08 m AOD
Monitoring details
Type Groundwater Level
Aquifer Permo-Triassic Sandstone
Confinement Confined
Depth 121.9 m
Record
Monitored by EA Wales
Records commence 1972
Records end Active
Map of Llanfair DC showing geology and water level contours

Hydrogeological setting

The borehole is in the Vale of Clywd, and representative of levels within the important Permo-Triassic Sandstone aquifer.

The borehole is drilled into the Kinnerton Sandstone Formation (Sherwood Sandstone Group) overlain by till deposits. It is possible that the sandstones are in hydraulic continuity with Carboniferous Limestone, which may contribute water to the aquifer.

The observed water levels are within the till, rather than sandstones, implying that the sandstone aquifer is confined.

Well or borehole construction

The well is 121.9 metres deep, lined to 18.59 metres, with a diameter of 248 mm reducing to 146 mm at depth. It was drilled as a purpose built observation well, with a secondary aim of establishing the geological succession.

The driller's log identifies a very porous zone between 98.8 and 100.6 mbgl.

Hydrograph response

The hydrograph shows a spiky annual sinusoidal pattern, within a relatively restricted range, with fluctuations generally less than 1 metre per annum.

Long-term trends are apparent in the data, with a slow rise through the 1970s, generally falling levels from 1985 to the mid 1990s and a relatively marked increase in levels to a record high in 2002. Since 2002 levels have fallen back slightly and appear to be relatively stable. It is assumed that these fluctuations reflect long-term changes in catchment water balance.

Data issues

Considered to be good, reliable data.

The borehole was previously numbered SJ15/15.

Contact

Contact Andrew McKenzie for further information