Rainfall generator for the Rhine catchment : a feasibility study

Methods for generating multivariate daily rainfall sequences for the Rhine catchment are reviewed. The request for such a review arose from the need to study the likelihood of extreme river discharges in the Netherlands, using a hydrological/hydraulic model. The rainfall generator must provide simultaneous records of daily average amounts over about 30 subcatchments, each with an area of about 5000 km2. The autoregressive or AR model for univariate time series of normally distributed random variables can easily be extended to the multivariate case. Especially the multivariate first-order AR model has been used to generate multisite daily rainfall data. This model generates dry days as negative values. A transformation of the daily amounts (often a power transformation) is necessary to achieve normality.