Friday, 11 November 2011

Leaving Lock Gates Open.

This posting has been prompted by a recent comment left on the blog. The merits of leaving a pair of lock gates open at one end of a lock is one of those questions that is discussed from time to time on the various canal forums. It's a bit like "pump-out -v- dump through -v- cassette" discussions. It's a very Lilliput like discussion, however it's not which end of an egg this time but the type of boat toilet. The rational for choice of toilet is down to the individual taste. However on reflection, maybe its choice not taste when discussing toilet options.

Reasons for shutting lock gates.

If there is a waterways directive about how to leave a lock set, such as closing both gates and paddles, then this should always be followed. Normal lock operation directives may cover the whole or a specified section of a canal. However, there are local directives that may modify the way that a set of individual locks should be left set.

Local directives that I have seen have included leaving gate paddles up two clicks such as at Rotherham Town Lock. This allows a small amount of water to be directed into the lower pound where there are linear moorings. There is a large river weir above the lock and so there is no chance of draining the section of river above the lock.

Why is there a need for the extra water to be flushed down. I think I have found one reason for the extra "leakage" in the pound to Eastwood Lock. I watched someone come out of the old Lock Keepers house and drain down the lock. This was after we had just ascend, leaving the lock full of water. Any boat now approaching from the top side of the lock will need to refill the lock again. You might think that this is not a major problem. However Eastwood lock is huge (it easily accommodates the Humber Princess a 60 x 6 metre oil tanker) and must have a fall of about 12-15 feet. So the pound above the lock will take a big extra hit of water every time a vessel descends or ascends. I am still puzzling as to why the lock is being drained other than to annoy people on the linear moorings at Tullys Marina.

Other local directives that I have come across have stated that a lock must be left empty on leaving. One such local directive is at Littleborough bottom lock on the Rochdale Canal. Most general directives that say lock gates and paddles must be closed on leaving a lock. Local directives notices are often attached to the lock balance beam or displayed on notice boards. I would imagine that the directives in most cases are intended to save water and the Rochdale Canal is one where water is problematical at times of low rainfall. Trying to reduce water leakage through locks that are approaching replacement due to their condition, is something we should all do.

It is a judgement call that we can all make as to whether to close both sets of gates. If the top pair of lock gates have significant leakage then I would always close both gates as a water conservation measure even when a local directive says leave a set open.

Reasons for leaving gates open are not always obvious.

Only expert local knowledge and good observational skills will help to decide where it is OK to leave one pair of gates open. Otherwise I would always defer to my default position of, all gates and paddles closed. This is after all how we will find most locks left.

If a lock has a by-wash and water is bypassing the lock down the by-wash then in this instance it could be reasonable to leave a set of bottom or top gates open. Most experienced boaters might make this judgement call. However, you would need to make up your mind by first observing what happens as the lock fills and empties. For instance, as the lock fills, does the water slow or stop running down the by-wash. If there is a significant change in the amount of water passing down the by-wash I would always close both sets of gates especially if the upper gates have a significant leak.

I have heard people say that leaving a set of gates open gives an exit option for none aquatic animals that may fall into a lock. I don't buy into this “animal safety” reason for leaving a set of gates open. Lock chambers account for only a tiny fraction of the length of canal. The chances of a wild animal falling into a lock is quite small. Now, think about all the miles of pilings that have been driven into the bank side. Ask yourself how do non aquatic animals get out then. If it was such a significant problem our canals would be full of dead animals. There are the odd fatalities but they are few and far between.

The only animal at significant risk of falling into a lock is us!

Most locks have one or more lock ladder points where we could make our undignified exit. Some lock gates even have hand and feet holds cut in them if the lock has no ladder. There is one thing that everyone should do and that is keep away from the edge of a lock. However, if you do fall in your life preserver will help you to float to the nearest ladder point. You do wear a life preserver at  all times don't you?

Any reason given for leaving a lock gate open, just doesn't hold water! So, unless I can see another boat coming towards the lock I always close the gates. If the lock is set against the approaching boat, I will open the sluices to start filling or draining the lock as needed.


1 comment:

  1. Mike, we read your blog, so thought you would like to know that on 3 Nov we saw dredger Ure moored above Rotherham Lock, and a panful of mud in the lock. Talking to the dredger skipper, they have a month's contract to do up to Ickles Lock.
    4 pans will be on the job, dumping the mud at Eastwood. Richlow guides


Please put your name to your comment. Comments without a name may automatically be treated as spam and might not be included.

If you do not wish your comment to be published say so in your comment. If you have a tip or sensitive information you’d prefer to share anonymously, you may do so. I will delete the comment after reading.