musings while allatsea

Musings of a curious individual

Going through the locks

I must admit the canals in the UK fascinate me, they are a rare glimpse of an age that has passed and which has become somewhat of the domain of the inland boater and canal fan.  I have never really been able to explore them properly, and only just see the occasional length of water in my travels. In Tewkesbury we have two major rivers: The Severn and the Avon, and at one point they are joined together through the Avon lock. The Avon Lock may be seen in the map below.

Just by chance I was there when a narrow boat traversed from one to the other.
At this point the narrow boat has turned across the Avon river and is now heading into the lock, the gates on the Avon being open, and the other side being closed. The water level inside the lock is the same height as that of the Avon.
I am now standing next to the open lock gates, the black and white beam is one of the arms of the gate which would have been manually operated but which is now electrically operated. You can just see the bow of the narrow boat on the right.
The narrow boat is now inside the lock and is being moored to the side of the lock, however, the mooring lines are not tied down, the one end is held by the skipper so that he can pay the line out as the water level drops. The lock gate is still open at this point. Now the gate on the Avon side gets closed with the narrow boat inside, the water level is still the same as it was.
This is the gate from the outside.
The water in the lock is now drained into the other side of the lock, lowering the level of the water till it matches that on the other side side of the lock.
Once the water level is the same the Severn side set of lock gates can be opened.
And the narrow boat can start moving into the Avon and a bit further down into the Severn 
and the gates can be closed once again, ready for the next customer. It can work in either direction, the only difference being that to rise up into the Avon water would be let into the lock from the Avon side. 
This whole process took 9 minutes according to the file information of the first and image above. 
It is as easy as that…
The Avon joins the Severn just a bit past the narrow boat in the image. 
Of course when the rivers flood the lock gates become moot anyway.
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