In message , at 12:28:56 on Tue, 6 Aug 2019,
NY remarked:
"Roland Perry" wrote in message
...
"Within the last few years new valves have been placed in the dam to
expedite rapid drawdown in emergencies: presumably, this is happening
now."

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

Precisely.

If the pumps are draining into the same waterways that the normal exit
valves (which now permit rapid drawdown) flow into, then there is no
advantage - unless the rate-limiting step is the rate at which water
can flow out of the drawdown valves, rather than the rate at which
water can flow away from the area.

If the pumps are draining into other waterways (eg rivers rather than
the canal system) then there *is* an advantage in using pumps because
it avoids overloading the canal

I'm wondering if they are using both.

- but the photos this morning
https://www.bbc.co.uk/news/uk-englan...shire-49247226 show the
pumps discharging onto the emergency spillway half way down on the
opposite side to the collapse, so into the same place that the
spillways and the normal drawdown valves go, which is presumably the
canal.

The spillways appear to drain into the River Goyt, while the water
that's drawn of for the canal is from a valve at the base of the
reservoir.
--
Roland Perry