Fuzzy C Means(FCM) clustering method and Self-Organizing Feature Map(SOM) clustering method were both employed to decomposed the flow hydrograph to several segments, and the situation of rain and runoff was analyzed in each segment, then two hybrid artificial neural networks (FCMMFN & SOMMFN), based on Fuzzy C Means clustering method and Self-Organizing Feature Map clustering method separately, were applied to simulate the rainfall runoff relationship. The case study in Wangjiachang Reservoir indicated that two clustering methods have the ability to decomposed the flow hydrograph to several segments in which the under-lying mechanisms of streamflow generation appear different. Besides, the two classification based artificial neural networks are both superior to the single multi-layer feedforward network, furthermore, the performance of FCMMFN is better than the one of SOMMFN.
