I have gotten the information I asked from PCC. (Thanks Jane.)
It turns out to have been Nick Walton (MSc CGeol CCghem, UoP) who gave that talk. The remark he made is not in the slides and not in the minutes and Nick is not at one of the water companies or the like. He is still at the UoP.
This is not the result I was looking for, but it was worth a shot. I remembered Nick as a member of the forum; I’ve e-mailed with him once or twice, but we were both only in the forum for a very short time. (I think he used to be known as Chemical Nick on a radio show? Or was that someone else?)
It still means that what I wrote earlier is true, that what he – Nick, apparently – said about the depth of the aquifer layers under Portsmouth or whatever exactly it was that gives Portsmouth an advantage relative to its surroundings in times of water shortages might be something worth protecting and preserving.