Statistical frequencies of plentiful and scanty runoff of different time series, including annual runoff, runoff of flood period, dry and irrigation seasons, in Hongze Lake, Luoma Lake and Nansihu Lake were analyzed on the basis of historical runoff data.For all of these time series' estimated encountering frequencies of high-flow or low-(low in both Hongze Lake versus Luoma Lake and Hongze Lake versus Nansihu Lake were presented in this paper.Finally, statistical analysis of high-flow year group or low-flow year group and encounitering frequencies of annual and flood season runoff were studied.Some ideas of optimum development and comprehensive utilization of water resources in the Huaihe and Changjiang river basins were suggested for the East Route Project of South to North Water Transfer in China.