I think you should add:--
  "Searching for, and obtaining planning permission for, a suitable site for the erection of a desalination plant for future use," 

This would be a safe guard against the failure of any new or existing ground water sources caused by excess drought, by neighbouring areas extraction rates causing a lower output from your new or exiting sources and to be ready to support more sharing with our  neighbours especially those without a coastal location. Such a site could be a source of income for Portsmouth Water.
I would also advise that the site is purchased well in advance of its need, that its solar panels are installed earlier than needed to power the plant and the current generated would  become a source of income until the desalination equipment is installed.  The actual design of the desalination equipment be kept updated on a regular basis ( as technical improvements are generated) so that the plant could be brought into use within a relatively short time. frame.