Estimating rainfall‐run‐off model parameters by non‐linear minimization

Existing discrete, linear rainfall‐run‐off models generally require the effective rainfall of a given storm as the input for computing the run‐off hydrograph. This paper proposes a rainfall‐run‐off model which uses the rainfall hyetograph as input and directly accounts for rainfall losses. The model combines an ARMA model and a modified Philip equation for rainfall losses due to infiltration. For a given watershed with measured rainfall hyetograph and the corresponding run‐off hydrograph, optimal values of model parameters are estimated by using a non‐linear iterative technique. Applications of the model to two different watersheds show that the computed run‐off hydrographs agree well with the measurements. The proposed model is a viable alternative to the widely used unit‐hydrograph method.