根据最近50余年资料研讨黄河、长江月平均流量的特征，揭示其若干演变规律。分析得出：长江中下游多年平均年流量约为黄河的20倍。初夏（6月）时，则接近50倍。黄河的大流量主要集中出现于 7～10月，这4个月平均月流量为全年的14.5%，其它8个月平均为 5.25%；长江流量自 5月起逐渐增加，5～10月平均月流量占全年的12.0%，其它各月平均为4.67%。最近50余年来，黄河中下游流量在1968年以前主要为正距平；1969-1985年基本正常；1986年起一直为负距平；加上人为因素，致使下游流量剧减迅猛，以致90年代以来连年有断流出现。长江中下游流量在1953-1955年为显著正距平；然后缓慢下降；90年代以后回升，1997年以后迅速上升，并出现几次大洪水。总之长江水源比黄河丰富且较稳定，黄河流量近10多年来则是贫瘠且多变。南水北调既是需要又有可能，尤其对解决北方春旱更为有利。

The monthly average discharge variations of Yellow and Yangtze River have been studied from the accumulated data in recent more than 50 years. Some interesting results have been shown that the interannual average discharge in the middle and low reaches of the Yangtze River is about 20 times of that in the Yellow River. The monthly flow of Yangtze River in the early summer (June) is about 50 times of that in the Yellow River. The significant flow of the Yellow River mainly appears from July to October. Comparison with other 8 months, the monthly mean discharge in each of these 4 months is about 14.5% of its total annual discharge, and in each of other 8 months, is only about 5.25%. The river flow of Yangtze River increases from May. The monthly average discharge from May to October is about 12% of its total annual discharge, out of this period, is only about 4.67%. In recent 50 years, the annual discharge anomalies of the lower reaches of the Yellow River was positive before 1968, was about normal from 1969 to 1985 and was negative from 1986. This negative anomalies tendency has been aggravated partly by the human behaviors, especially in the ninety’s, it has resulted in the river flow sharply down and even leaded to interrupt the river flow frequently in the lower reaches of the Yellow River. Comparatively, there were a significant positive anomalies around 1953 to 1955 in the middle and lower reaches of the Yangtze River, after that it slowly decreased, then it was back to increase in the ninety’s. An obvious increase appeared in 1997 to 1999, and was associated with several severe floods in the ninety’s. All the evidences have shown that the Yangtze Rive has more water resource and more stable than the Yellow River. And the water resource in the Yellow River is varied and deficit, especially in the recent decade. So that the South-to-North Water Transfer Project is necessary and is a possible way to solve the water shortage in the North China, especially in the Spring and the early Summer.