"Robin" wrote in message
...
Although the question being asked in this thread is "if that's the case,
why also use lots of pumps".

well I don't claim to have any engineering qualifications but it seems to
me a plausible answer is in the public statements:

- the spillway was damaged leading to a risk of catastrophic failure,

- there was a lot of water in the reservoir

- water was still coming in at a high rate (and with the risk of more rain
to come)

so it seemed like a good idea to lower the level faster than would be
possible without the pumps (with the added benefit of being able to send
water to different places and so avoid downstream flooding).

To the best of my recollection and belief, all the above is on the public
record.

But then some prefer speculation.

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.