RELEVANCE OF THE H2U MODEL TO PREDICT THE DISCHARGE OF A CATCHMENT

The new deterministic model H2U (from French ''Hydrogramme unitaire un iversel'') is validated for two Mediterranean catchments, both in natu ral conditions, in the south of France and in the very anthropic catch ment of Paris-Orly airport. It starts from a description of the draina ge network by means of a density function of the hydraulic lengths. Th rough the mean water speed in the channels, this function is proved to be the unit hydrograph, or transfer function of the catchment. Moreov er, in some cases, the production function can be directly known, for instance when the rain intensity is very high, or, if rain intensities are rather low, when the impervious surface area ratio is known and c an be considered as the effective rainfall/total rainfall ratio. Then, the H2U model can give directly a good simulated curve of discharge, without any calibration except for the estimation of the mean water sp eed. The model can probably give good simulations in any situation pro vided that the production function has been evaluated. Even better, it can be used as the known kernel function in order to obtain the effec tive rainfall, i.e. the production function, by deconvolution of the a ctual hydrograph. (C) 1997 IAWQ. Published by Elsevier Science Ltd.