In 1991 I described a particularly simple and elegant water-shed algorithm, where the ooding a topographic surface was scheduled by a hierarchical queue. In 2004 the watershed line has been described as the skeleton by zone of inuence for the topographic distance. The same algorithm still applies. In 2012 I dened a new distance based on a lexicographic ordering of the downstream paths leading each node to a regional minimum. Without changing a iota, the same algorithm does the job.