According to many years'meteorological data,it may be seen that the probability of plenty or deficiency of water at the same time both in the South and North of China isn't very great,it is about 25% only.The rule of the seasonal distribution of precipitation is that,in spring,irrigation needs water at the same time the Yangtze River has surplus water;in summer,when the Yangtze and Huaihe River Basins have less rainfall and the Haihe River Basin is Just in rainy season;in autumn,both South and North China have surplus water,we may fill the reservoirs for winter and spring irrigation;in winter,the surplus water of the yangtze River may be tranferred to the North to supply water for winter irrigation.Therefore to transfer water from South to North is possible and fit also.