Farakka Barrage: the Ganga works that keep the Kolkata Port navigable
Background
The Farakka Barrage Project (FBP) was commissioned in 1975 for preservation & maintenance of the Kolkata Port and for increasing the navigational depth of the Bhagirathi - Hooghly waterway.
The Farakka barrage in West Bengal regulates the flow of the Ganga, diverting some of the water into a feeder canal linking Hooghly to keep it relatively silt-free.
Downstream of the barrage the Ganga splits into two: the Bhagirathi (Hooghly) on the right and the Padma on the left, which enters Bangladesh.
The project has a total of 123 gates, and phase wise replacement of the gates of the main barrage and of the Head Regulator has been undertaken by the project authority.
Farakka is the last control structure on river Ganga in India, and the flow in the Ganga/Padma river and in the Farakka canal is regulated as per the India-Bangladesh Treaty-1996.
Under that Treaty the Ganga/Ganges waters are shared at Farakka during the lean period, from 1st January to 31st May every year, on a 10-day period basis as per the formula provided in the Treaty.
In plain words
Barrage — A low gated structure across a river that raises and regulates the water level without storing a large reservoir.
Feeder canal — A canal that takes water from a barrage and carries it to another channel; at Farakka it links the Ganga to the Hooghly.
Head regulator — The gated structure at the mouth of a canal that controls how much water enters it.