A monthly model and two daily models (I and 11) are presented for the purpose of generating monthly and daily rainfall sequences in the Quae Yai river basin in Thailand. Performance of the models are evaluated by comparing the statistical parameters of the generated sequences with those from historical data. For monthly generation, Thomas-Fiering model worked satisfactorily in spite of the monthly correlations being weak, if any. Daily Model I, which assumes no persistence between daily rainfall amounts within the wet spells, could not preserve some important parameters regardless of the simplicity in model construction. Application of multi-state transition probability matrix model gave good results, although the user has to modify some parameters looking at the performance of the model for each historical record.(KEY TERMS: rainfall generation; stochastic models; Markov chain models.) pel. = average rainfall of month j J IS. = standard deviation of rainfall in monthj J p . = correlation coefficient between the rainfall amounts in monthj-1 and monthj J t = gamma distributed random variable with zero mean, unit variance and coefficient of skewness equal to ytThe coefficient of skewness, y t , is estimated using the formula

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Runoff Routing model (RORB) is a general model applicable to both rural and urban catchments. The performance of the model is illustrated through its simulation of flood runoff hydrographs in an urban catchment in Singapore. The essential feature of the model is the routing of rainfall excesses on subareas through some arrangement of concentrated storage elements, which represent the distribution of temporary storage of flood runoff on the watershed. This nonlinear routing procedure of the storage elements has two common parameters, kc and m. With the limited data available, these two parameter values were determined through calibration runs. The same set of values of kc and m were then used in the model to determine the runoff hydrographs of five other storms selected from the rainfall events between 1979 and 1981. It was found that the simulated runoff hydrographs matched reasonably well with the recorded hydrographs.