Rainfall field estimates for hydrological models

Abstract

The rainfall input in hydrological models concerns the mean area precipitation (MAP) values at a certain time resolution, which is required to be higher and higher in the rainfall-runoff modelling, but using space sampled data there is a limited MAP accuracy with respect to the involved time scale. Improved estimates of the rainfall field at small time intervals combine more accurate MAP values performed at a larger scale with the point time variability of data. The usual observation time scale for rain events is 1 h, with acceptable MAP errors, and according to the counting-box method applied in the case of the rainfall contour length there is a scale invariant below such a value. This paper suggests that an improved rainfall input may be obtained by transferring the shape of the hourly rain intensities to each hour in order to generate a finer time distribution of the MAP values, this being accepted if it leads to a better fitting of the simulated and observed hydrographs. This assumption is investigated by numerical experiments with a rainfall-runoff model at different catchment areas.