Dicky Mountbatten’s All Knowing Shannon Almanac

Today on the river

Daylight

Locks

Portumna Bridge openings

Phone

Lake forecast

No forecast stored yet.

Marine notices

Live notices as of 13 Oct 2026

All live marine notices on waterwaysireland.org. New notices are picked up from Waterways Ireland's email list every two hours.

Time to travel

From To Leaving at

Cruising

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Arrive about

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Cruising hours from the shannon-river.com distance chart, counted only between sunrise and 30 minutes before sunset, plus 20 minutes per lock, Waterways Ireland lock hours and lunch breaks, Portumna Bridge openings and announced closures. Allow extra for the weather.

Depth correction

Untested experiment, not an aid to navigation

Everything above is published data: gauge readings, timetables, forecasts and notices. Everything below is this page's own arithmetic on top of a chart datum that nobody has confirmed against the water. Treat it as a guide to check with your lead line and the markers, never as permission to go somewhere.

Correction to charted depths

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Loading the latest gauge reading…

Checking

Under-keel figures are judged on the shallow end of the band, with no allowance for squat or waves.

Depth at a spot

Charted depth metres, from the CSIG chart Your draft metres, remembered on this device

Water there now

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Under your keel

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Check it with your lead line

Charted spot depth metres, from the CSIG chart Lead line reads at the water surface Line marked in remembered on this device

Where optional, e.g. off Dromineer When leave blank for now

How to take a good check

Pick a charted spot depth on a flat, even bottom, away from drop-offs, so being a boat-length off the spot doesn't matter.
Stop the boat. Lower the lead until the line goes slack, then lift until it just touches, with the line straight up and down.
Read the mark at the water surface, not at the deck or the gunwale.
Take three casts and enter the middle one. Soft mud and weed let the lead sink, so a firm bottom gives a truer reading.
Choose a calm spell: wind piles water up at the downwind end of a lake.
Check the rope's marks against a tape now and then. Rope stretches and shrinks when it's wet.

Water against chart datum

Water level
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Chart datum
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Over the cill
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Metres above Ordnance Datum Malin Head.

Enter a reading yourself

Gauge level m OD Malin, or staff gauge

Feet over the cill e.g. 8.25

Chart datum

Cill heights in m OD Malin Feet over it from the CSIG chart

Official reports

Waterways Ireland's report lists each lock's ordinary summer level and the 9:00 reading, published by 9:30 on weekdays (weekend readings appear on Monday). Its levels and the ESB's are in Poolbeg datum: take off 2.71 m to compare them with this page. Ardnacrusha uses about 100 m³/s per turbine, so around 400 means all four are running and Lough Derg is being drawn hard.

Keep in mind