Abstract: One of the major risk factors in managing water resources in the middle route project of South-to-North Water diversion will be due to spatial and temporal variations in precipitation.This is because the synchronous-asyn-chronous encounter probability of rich-poor precipitation can be different at the source area of water and at the receiving area of water.In this study,a risk analysis model is developed using a combined approach based on the copula function and Bayesian networks.The copula function is used to establish the joint probability distribution and to calculate the conditional probability among the areas of source water and receiving water.The Bayesian network is applied to analyzing the synchronous-asynchronous encounter risk.Using the risk analysis model,a risk analysis is conducted to determine the lease favorable distribution of the synchronous-asynchronous encounter probability of rich-poor precipitation at different locations.The result shows that the risk probability is less than 25% for water transfer to four receiving areas.Our risk analysis model is simple and practicable,and can provide a new tool for conducting the multi-variate analysis of hydrological risks.