Holyhead tide gauge site

The tide gauge building is located on Salt Island close to the lighthouse in the Port of Holyhead.
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Tide gauge location

The brick tide gauge building contains two stilling wells. A Munro IH40 chart recorder is mounted over one of the wells. The building also houses the POL data logger and pneumatic control panel. The pressure points are mounted directly below the building.

The tide gauge is levelled to the tide gauge bench mark supported by Ordnance Survey auxiliary marks.

External users

There are currently no external users.

Site history

1958 – Lea gauge installed in the inner harbour
1977 – Lea gauge replaced, Ott punch tape recorder installed, Lea gauge removed
1977 – Lege gauge replaced with an Ott R16 gauge
1978 – New tide gauge site established on Salt Island
1978 – DATARING system installed with a full tide bubbler and a potentiometer on the Munro gauge
1991 – Mid-tide bubbler installed
1991 – Ship collided with the tide gauge building causing extensive damage
1991 – Tide gauge building demolished
1992 – Mid-tide pressure point installed
1994 – New tide gauge building constructed
1995 – DATARING system installed with a full tide and mid-tide bubbler and a potentiometer on the Munro gauge
2000 – New POL data logger installed

Latitude53° 18.834'N
Longitude4° 37.224'W
Grid refSH 2553 8287
Earliest data1964
Tidal levels
HAT6.33 m
LAT0.00 m
MHWS5.66 m
MHWN4.51 m
MLWN2.02 m
MLWS0.71 m
H for 2024 6.30 m
L for 2024 0.00 m
H for 2025 6.19 m
L for 2025 0.08 m
MSR4.95 m
MNR2.49 m

HAT – highest astronomical tide
LAT – lowest astronomical tide
MHWS – mean high water springs
MHWN – mean high water neaps
MLWN – mean low water neaps
MLWS – mean low water springs
H – highest for year
L – lowest for year
MSR – mean spring range
MNR – mean neap range

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