Closing address

H E water supply system and its dirty water continuation are extremely complex. It has, in common with all complex systems the fact that it is not always easy to understand the possibilities that exist within it, all the interactions which can and perhaps should occur. It is not easy for one group of people responsible for managing an enterprise like a water authority to have before them what is necessary to make an individual judgement. This is an area where there never is and never will be enough data. But engineers and managers have to live with that situation and cope with it.