ON THE CONCEPT OF A REPRESENTATIVE ELEMENTARY AREA IN CATCHMENT RUNOFF

A qualitative discussion is presented on the concept of a representati ve elementary area (REA) proposed by Wood et al. (1988). Their work re presents a systematic effort of looking at spatial variability as func tions of scale, and over the past few years has stimulated new thought s and research findings. However, it is argued here that the REA conce pt has limited utility in catchment hydrology for the following reason s. Firstly, the method of finding the REA using distributed modelling appears flawed. In estimating local runoff, point-process models are a pplied to elements of 30 x 30 m(2) or larger, but the effect of this p articular upscaling on the calculated REA has not been addressed. This causes the REA to be relative to the resolution of the modelling. Sec ondly, an REA does not seem to exist in a natural environment because of its relativeness in the presence of multi-scale heterogeneity and i ts dependence on individual storm events. Based on the above arguments and following a discussion of the hydrological implications of REA, i t is pointed out that the REA does not provide a definite and robust m easure of the inherent spatial variability in runoff and that its util ity in formulating large-scale hydrology is not as clear as it was fir st envisioned.