CAN ONE GAUGE THE SHAPE OF A BASIN

This paper investigates the effects of geometrical factors characteriz ing the shape of a river basin on the features of its hydrologic respo nse. In particular, we wonder if by measuring the hydrologic response (i.e., gauging) the salient geomorphic features of the basin can be re covered. We argue that the basic structure of the channel network tend s, in ideal conditions, to yield some universal characters of the widt h function W(x) defining the relative proportion of a contributing are a at a distance x from the outlet. W(x) exhibits low-frequency feature s, which are geometry-dominated, and high-frequency features determine d by recurrent aggregation patterns. It is suggested that given the sh ape of the basin one can indeed forecast in a rational manner the main characters of the hydrologic response which are imprinted in reproduc ible width functions. However, the inverse problem (i.e., the determin ation of the shape from the measure of the hydrologic response) is les s solidly defined because of the possible loss of irretrievable inform ation induced by the dynamics of runoff processes. Therefore the quest ion posed in the title cannot be solved in general, although many elem ents for a general theory are seemingly established.