Fen Management Handbook - Scottish Natural Heritage

Box 2: Construction, installation and monitoring of a dipwell
Dipwells can be bought ready-made, or home-made, as described below. DIY construction
allows ‘bespoke’ dipwells to be made, but there are a large number of considerations to be
made in deciding the design. For example:
Diameter; dependent on what needs to be inserted into the dipwell, e.g. small pump for
cleaning, pressure transducer apparatus.
Length: dependent on the depth of insertion (must cover only the range of fluctuation
of the soil water level) and the length of dipwell protrusion above the ground surface.
Dipwells can usually be ‘cut-down’ on insertion to attain the correct height.
Response zone; most commonly holes are drilled throughout the length of the dipwell,
allowing water ingress over the whole depth, but it is possible to measure water pressure
at specific depths by only drilling holes over a specific interval, e.g. the bottom 30 cm.
Design & construction. A dipwell is a narrow (usually c. 20 – 50 mm diameter), normally
plastic tube with drilled holes or slots to allow water ingress. The tube is fitted with an
internal basal cap (to prevent ingress of sediment on insertion), and is usually wrapped in
a filter sock (kept in place with cable ties) to prevent ingress.
Installation. Dipwells are usually placed in hand-augered holes. The diameter of the hole
is determined by whether or not the dipwell is going to be pushed directly into the hole
or whether it is to surrounded by a ‘gravel pack’. The sediments encountered, and the
behaviour of the soil water level, should be recorded during augering. It is recommended
that the dipwell cap is secured with a grub screw. If the elevation of the dipwell will be
vulnerable to change, for example by cattle tread or expansion/contraction of peat, a solid
datum (anchored into the solid mineral substratum), usually a metal pole or a wooden
stake, should be installed.
Monitoring. Relocation of dipwells after installation can be very difficult, especially if a
dense under-storey of vegetation has developed! Techniques which can be used for
re-location include using a GPS or leaving a marker stake in the ground next to the
dipwell. Water levels can be measured periodically, using
an electronic dipmeter, or a tape measure if soil water levels
are close to the surface. Levels will usually be measured
downwards from the top of the dipwell (datum), but can also
be measured upwards if the dipwell is underwater. Water
levels can also be measured at high frequency (effectively
continuously) using pressure-transducer and data-logger
apparatus; this is a more expensive option but it does
generate a higher quality dataset.
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