Analysis on the Characteristics of Runoff Time Series in Akesu Basin
新疆阿克苏河流域年径流时序特征分析

Akesu River is one of the largest rivers in northwest of China. It is the main tributary of Tarim River, whose upper branches are in the territory of Kirghizstan. Akesu basin lies in arid and semi-arid region of China, and it has typical hydrographical characteristics of inland rivers in northwest of China. Using forty years' annual discharge at five representative gauging stations in Akesu basin, this paper presents several runoff statistical parameters, namely variation coefficient, concentration ratio, concentration period, kurtosis, wet-dry transformation ratio, and the curve of difference accumulation and probability density. It is the fundamental purpose of this paper to analyze annual distribution and change of discharge from year to year with different runoff-supplying sources in Akesu basin. The result shows that the runoff-supplying sources in Akesu basin have vertical zonality and diversification .The characteristics of annual discharge in Akesu Basin have close relations with runoff-supplying sources. The allocation of discharge is extremely uneven, and has a quite high concentration within one year. On the other hand, for many years, variation coefficients of annual discharge have much lower value than other rivers in south of China. The high and low flow years alternate in these years, and the probability distribution approximates to normal distribution. There are not enormously wet and dry years, and the tendency of annual discharge change is relatively steady.