Weather Update

A tide is the regular rise and fall of the sea level. At Gangasagar the sea (Bay of Bengal) and the river mouth (Hooghly / Muriganga) slowly rise for about 6 hours and then slowly fall for about 6 hours – again and again, every day.

Mainly the Moon’s gravity pulls the ocean water. It makes a bulge (raised water) on the side of the Earth facing the Moon and another bulge on the opposite side. As the Earth turns, a place like Gangasagar passes through both bulges and both low parts every day. The Sun also pulls the water, but with about half the force of the Moon.

High tide (জোয়ার / ज्वार) is when the water reaches its highest level – the sea comes up the beach and the river is full. Low tide (ভাটা / भाटा) is when the water is at its lowest level – the sea moves far back and sand and mud flats are seen.

It does not disappear. During low tide (ebb) the water flows out of the river and away from the beach into the deep Bay of Bengal, towards the area under the other tidal bulge. The same water comes back with the next high tide.

From the open sea. During high tide (flood) the raised ocean water of the Bay of Bengal flows towards the coast and pushes up into the river mouth – so at Gangasagar the sea comes up the beach and the Hooghly and Muriganga rivers fill up, and the current even flows upstream.

Usually two high tides and two low tides in about 24 hours 50 minutes. From high tide to low tide is about 6 hours 12 minutes. See the 7-day tide table on our Weather & Tide page.

The Moon comes back over the same place about 50 minutes later each day, so each high tide and low tide is also about 40 – 60 minutes later than the day before.

On Purnima (full moon) and Amavasya (new moon) the Sun and Moon pull together – high tides are higher and low tides lower (spring tide, strong currents). Near the half-moon days (Ashtami) the pull is weaker and the difference is small (neap tide).

The Hooghly river mouth has a large tide. At Sagar Island the difference between low and high water is roughly 4 – 5 metres on spring-tide days and about 2 – 3 metres on neap-tide days (approximate – it changes with season, wind and river flow).

The Muriganga river is shallow at low tide, so government vessels and launches mostly run when the water is high enough. At low tide services can be stopped or delayed and the queue becomes long. Always check the live ferry time and tide table before you start.

Take the dip only at the marked ghats, near police / volunteers, and only up to waist-deep water. The current is weakest around the turn of the tide (just at high or low tide) and strongest in between. Do not go far out on the mud at low tide – the water comes back fast. Senior citizens and children should always have someone holding them.