Abstract
A new method to predict runoff for long lead time based on fuzzy theory by utilizing the qualitative prediction information of future rainfall is developed in this paper. The method consists of two main calculations which are: (1) establishing the fuzzy relation between rainfall and runoff according to the past flood data; (2) inferring the future runoff based on the above fuzzy relation by inputting the rainfall data. The prediction information about future rainfall is supposed to be presented in such several ranks as: weak, medium, strong and very strong, etc. The paper handles this kind of qualitative rainfall ranks by introducing their membership functions which are defined subjectively and reasonably. The method is applied to Butternut Creek, NY. in the USA. to make 1hr∼6hr lead time forecasts of runoff. The good results indicates that the proposed method is successful for runoff prediction.
