This sankey diagram illustrates the water flows in Amsterdam. It makes the importance of each of the flows immediately clear. There is one confusing aspect to this diagram: the patterns used (horizontal lines, diagonal lines, etc.) are not explained in a legend and seem to have no particular use (if you look closely, each pattern is unique and does not repeat itself). Ideally, patterns should be used to mark a particular characteristic of the flow.

From the publication:

Overview of water flows (in kt) in Amsterdam's metabolism (excluding industry water).