The circumfluence around the Jiuduan Sandbank is thoroughly studied by mean
s of the principle of least resistance in fluid dynamics. The diversion rat
io of the North Channel for 1998 is calculated, which is almost the same as
the field survey data. The normal and minimum diversion ratios of the Nort
h Channel after stages I , II and III regulation works as well as the futur
e phase are obtained. The numerical results and predicted value are accurat
e.