The paper discusses concepts and developments within water quantity, water quality, integrated environmental assessment and wastewater treatment. The historical and the global perspectives are used in the discussion of the role of engineers in today's society. Sustainabilty and ethics are taken into the analysis. There is a need for re-evaluation of the resource, society and environment scenarios with a view to the totality of the system and with proper analysis of the flow of water and matter through society. Among the tools are input-output analysis and cradle to grave analysis, in combination with compilation of identified sets of values with respect to sustainable use of resources and ultimate fate of the environment and quality of life. The role of the engineer is to make available to society as many technical options as possible - and to put these options into the proper perspective in relation to the objectives of society.