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黄河上游的水文情势有许多独特之处。它的源地一带比较湿润,水量较丰,千里迢迢蜿蜒曲折地把水送往我国北部最干早的地区,开辟了塞北江南的广大宁蒙灌区。它的径流年内年际变化都相对比较均匀,年径流的变差系数为O.2～O.3,是国内大流域中的较小者。兰州以上的年径流模数高出全河2.1倍,水量占全河的58%;洪水涨落平缓,洪峰流量模数只及其
The hydrological situation in the upper reaches of the Yellow River has many unique features. Its source area is relatively moist and abundant in water. The twists and turns meandering its way to the driest region in the north of our country and opening up the vast Ningmeng Irrigation District in southern Saibei. The annual variation of its runoff is relatively uniform, and the coefficient of variation of annual runoff is O.2 ~ O.3, which is the smaller one in the domestic large watershed. The annual runoff modulus above Lanzhou was 2.1 times higher than that of the whole river and the water volume accounted for 58% of the whole river; the flood fluctuated gently and the flood peak flow modulus only matched