Applying the methods of stable isotopes and hydrochemistry to study the leakage of dyke is an effective way. But men only qualitatively analysed and judged the problem. The authors attempted to perform the analysis of fuzzy clustering by applying fuzzy clustering method that stable isotopes and hydrochemistry values of 22 water samples were taken as index characteristic values and endued different weightings

combining the case of Beijiang Dyke. The clustering result shows that there is great interrelation about stable isotopes

Cl- and TDS among the water samples of T12 borehole

water gushing at 5m north to T9 borehole

river water and out-waters of drainage gallery north to T9 borehole. It is a proof to judge the leakage passage that the water samples may has the same replenishment source.