I was at Yorkshire Water during the mid-90s drought, manic times. We did build a pipeline at YW, yes – the Tees-Wiske transfer.
The last few km weren’t connected though, as it’s a measure of last resort. The water chemistry is significantly different and plonking that water into the Wiske would have a rather big impact on the ecology. So YW would only be likely to be allowed to use it in extremis, as they’d need permission from the EA.
The cost-benefit trade-off would come down to societal needs vs the environmental damage. The industry has done a lot in the last 15 years or so on cost benefit analysis, so it’d be interesting to see how that panned out.
I imagine we’ll be seeing a fair bit of that in the future as the effects of climate change become apparent. The ELL should shift so I’d anticipate that leakage levels will be driven lower to some degree but that’s not a foregone conclusion.