On 05/08/2019 11:32, NY wrote:
"Mike Clarke" wrote in message
...
On 05/08/2019 10:18, NY wrote:

I may have missed something in the earlier new reports, but why are
they having to *pump* water out of the reservoir? Is there a problem
with taking water out in the normal way? I think it's a canal feeder
reservoir. Can the canals not cope with a greater flow of water into
them than was originally intended?

Canals weren't designed to carry a significant flow of water.

They're a series of long thin "lakes" connected by locks where there's
a change in level. Every time a boat passes through a lock a lock's
worth of water escapes from the higher section to the lower one. Apart
from that there's very little flow.

Presumably canals have to be capable of carrying a flow of water
equivalent to each lock being opened every so often to let narrow boats
up or down. How big is "a lock's worth", typically, in terms of the
amount of water the flows into it when the upper gate is opened and
flows out when the lower gate is opened? I imagine it's fairly small
compared with the 7000 litres (7 tonnes) of water that were being pumped
out every *minute*. Do canals tend to have a maximum boat movements per
day limit, not just because of traffic congestion at the locks but
because of the flow of water through the canal which could scour its sides?


Figure usually given as 100,000 gallons per lockful