Urban Water Management involves the fields of water supply, urban drainage, wastewater treatment and sludge handling. On the basis of the Agenda 21, principles and guidelines for sustainable urban water management are discussed. Sustainable technology leads to acceptable gradients in state variables. New technologies departing from an analysis of required services rather than stepwise improvement of existing technology is preferred. An efficient use of resources will lead to a minimal increase of entropy and will require an active rather than a reactive approach. The analysis of the transition period from today's to a sustainable situation is important. An example is introduced which deals with global cycling of nutrients and which may be approached on a regional scale.