In message , at 09:31:27 on Tue, 6 Aug 2019,
NY remarked:
"Roland Perry" wrote in message news:h7aW3xpsdSSdF
...
In message , at 12:54:36 on Mon, 5 Aug
2019, NY remarked:
What is the typical number of lock-emptyings per hour that a canal
can handle?
Depends on the size of the paddle-gear. But one lock every five
minutes is about the fastest one would normally achieve.
However, you don't do it like that - the correct method is to open
the paddles both ends, which will at least double the flow compared
to a lock full ever five minutes.
Ah yes, I was forgetting about the paddles (I, too, would have called
them sluice gates, but I stand corrected)
They are a form of sluice gate, so it's not a big issue. Paddles can
either be in the gates themselves or in tunnels to the side of the gates
(and are then called "ground paddles"). Some busy locks have both.
which would be needed anyway to fill the pound before the upper gates
could be opened.
So if you needed to transfer a lot of water in the shortest time, how
long could you leave the paddles of all the locks open without damaging
the sides/bottom of the canal by scouring?
Indefinitely (well, in the timescale of an incident like this). The
bottom paddles (and especially bottom ground paddles) unleash massively
turbulent water that can be quite a risk for any boats caught up in it.
And have been doing it at every lock for hundreds of years.
I wonder if that is being done in parallel with pumping water directly
out of the reservoir into non-canal waterways?
That's my question. Is it happening and no-one has reported it, or is
there some specific reason it's not being used.
450,000 litres
That number's too big. A narrow lock of the kind round there is
typically 150,000 litres.
https://www.whatdotheyknow.com/reque...4783/attach/17
/Water%20Management%20FAQ%20s%20parts%201%20and%202 .pdf
There's also some numbers in there for the capacity of pumps used on
some waterways to re-circulate the water.
Note also their estimate of ten minutes per lock cycle includes
manoeuvring the boat in and out, as well as the actual filling and
emptying.
every 5 minutes by the lock paddles is a hell of a lot more water than
7000 litres every minute by the pumps. But that is making the big
assumption that it is OK to drain a lock's worth of water every five
minutes as a sustained rate over many hours, rather than just a burst
rate with gaps in between.
If a canal has been emptied for maintenance (or because a careless
boater has left a paddle open overnight) it's perfectly routine to just
open all the paddles fully and wait, possibly hours, for the affected
levels to restore.
--
Roland Perry