German Locks

[woofas]

On a trip through the Danube-Main canal, our guide claimed that when a ship passed through an individual lock, 60% of the water was re-used without the use of pumps! This was because each lock had three associated basins and connecting valves. Anyone know where this system is described?

[sddsddean]

They are called 'side ponds' and are still used on the canals in the UK, but in a much simpler form. Lets assume you are going up hill and the lock is full. Instead of draining the lock and losing all the water, half is drained off into the side pond by an intermediate paddle (sluice). After half the water has gone, this paddle is closed and the remaining half lock drained to the lower level. You enter the lock. Now we half fill the lock with the water from the side pond. The remaining half of the lock is filled from the top canal level. Hope this gives the general idea. Many continental locks use multiple side ponds at different levels. I'm sure you can see that with, say, 3 side ponds at different levels, it is possible to use only a quarter of a lock per cycle; the water in the side pond is effectively moved down one 'step' each cycle.

[samsong7]

Deans correct with his description of these locks.
Copy and paste this link for more info
http://foxtonlocks.com/sections/boaters/theloc ks/index.php

[woofas]

Thanks for your response but I think I confused everyone by referring to basins rather than side ponds. Also, in this instance the description was being applied to an individual lock rather than a staircase. I can see that a single side pond will allow you to save half of the water when emptying and consequently save a quarter (25%) when refilling and completing the cycle. But try as I may I cannot see how three side ponds, even at different levels, allow 60% to be re-used.

[sddsddean]

In the example with the 3 side ponds, the lock would be emptied in 4 stages. So at the start of a cycle of 4 'openings', the top quarter of water will go into the top pond, next cycle it will effectively go from the top to the middle, then middle to bottom, then bottom to out of the lock. You could say that this 'bit' of water is all that is lost in a cycle, so only 25% of the lock is lost per cycle. This means 75% must be saved for re-use. As everything would have to be amazingly efficient to achieve exactly 75% saving, they probably say they only re-use/save 60% per cycle.