In message , at 13:10:36 on Fri, 9 Aug 2019,
bert remarked:

The one thing I've not seen mentioned anywhere is whether they have
been emptying the reservoir by the normal route (valves draining into
canal system) in addition to the much-publicised pumping operation. I
presume they have, but it's not (that I've seen) been mentioned.

Exactly. Have they decided not to, or has it just escaped the attention
of the civilian press?

Well it would beggar belief if they *havent* opened the normal drain
valves but I imagine that theyre not designed to empty a reservoir
quickly. After all, if you have a working spillway why would you need a
humongous drain valve?

Because the spillway only works when the reservoir is 101% full, and you
need to drain them when 100% full.

The reservoir already has an outlet to feed the canals and probably another
€œservice drain€�. Im sure that they were using all all available drains
before bringing in pumps. Why wouldnt they?

Agreed. I'm more interested in why it's not been reported. Just lack
of observation perhaps?

Probably. No very visible and not as exciting as fire engines and lots
of pipes and pumps.

That's gets my vote for the most likely answer.

Also not straightforward to dump loads of water into the canal system.

Although it's incredibly straightforward. One bloke just needs to open a
handful of sluices (to use a generic name).

The pumps were emptying into the river.

And they will have calculated whether there was going to be any
collateral damage downstream. The river doesn't have infinite capacity
any more than the canal.
--
Roland Perry