To give form and content to integrated water management, we often apply an internal approach, based on the component parts. With this approach we encounter at least three problems: the problem of scale, the problem of level and the problem of assessment. We can solve these problems by applying an external approach to integrated water management, in addition to the internal approach. This is possible by application of the theory of complexity. It turns out that we can describe the sum of the processes within integrated water management as a complex adaptive system, a learning and evolving system. If we use this system as a model, we come to the insight that we must not try to achieve as much order as possible, but that we have to look for a good balance between order and chaos. If we find that balance, we are able to adapt water management to the ever changing surroundings.
The usefulness of the approach becomes clear if we look at the discussion in urban water management about the applicability of source control and end-of-pipe techniques. The approach provides a strategy for handling uncertainties.