Rainfall forecasting plays many important role in water resources studies such as river training works and design of flood warning systems. Recent advancement in artificial intelligence and in particular techniques aimed at converting input to output for highly nonlinear,non-convex and dimensionalized processes such as rainfall field, provide an alternative approach for developing rainfall forecasting model. Artificial neural networks (ANNs), which perform a nonlinear mapping between inputs and outputs, are such a technique. Current literatures on artificial neural networks show that the selection of network architecture and its efficient training procedure are major obstacles for their daily usage. In this paper, feed-forward type networks will be developed to simulate the rainfall field and a socalled
back propagation (BP) algorithm coupled with genetic algorithm (GA) will be used to train and optimize the networks. The technique
will be implemented to forecast rainfall for a number of times using rainfall hyetograph of recording rain gauges in the Upper
Parramatta catchment in the western suburbs of Sydney, Australia. Results of the study showed the structuring of ANN network with
the input parameter selection, when coupled with GA, performed better compared to similar work of using ANN alone.