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"Tides" & Currents on the Lakes


Tides:

Because the Lakes are vast (450 sq-miles) and the entrances to them narrow, the twice-daily tides which affect our coastal waters have little significant effect on the water levels on the lake; wind and barometric pressure can have a greater effect. Strong winds, especially if prolonged, can cause significant variations in water level. Also, extended periods of high pressure will lower the water level and periods of low pressure will raise it. Heavy rains, too, can raise the water level significantly. Expect variations in water level of up to a foot (30 cm).

Currents:

Buoy Q8
Ebb tide rushes past buoy Q8 in the Great Bras d'Or Narrows. Photo —Ken Heaton

Strong currents will be experienced in the Great Bras d'Or Narrows and the Little Bras d'Or inlet These currents are predictable and published in the Tide Tables. However, for the reasons noted above the time of slack water in the narrows may occur earlier or later than predicted by half-an-hour or more, and this should be borne in mind when timing a passage through these channels, especially for slower craft.

The narrows at Grand Narrows and Little Narrows are also subject to significant currents. As the Lakes are a major drainage basin there is a net flow of water towards the sea, but there are "ebb and flood" currents. There seems to be no predicting these currents as they are mainly due to fluctuations in water levels which have little relation to the ocean tides. Caution is advised when passing the bridges at Grand Narrows as the navigation channel is narrow and subject to eddies. The only hazard at Little Narrows is the ferry: caution is needed to avoid being swept into it while awaiting passage.

Revised: 2014-06-02

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