In this researsh, the characteristics of inter-annual variation and inter-annual distribution of runoff in the upper reaches of the Bailongjiang River were analyzed by using the monthly runoff data during the 46 years observed at the export control station, Baiyun Hydrologic Station. The analysis was conducted by using different indexes, including annual runoff variation, monthly runoff ratio, annual runoff inhomogeneity coefficient, runoff concentration ratio (or period) and changing amplitude. The research results show that the annual runoff in the upper reaches of the Bailongjiang River was decreasing and concentrated temporally around August 15. In addition, the general long-term runoff change trended to stable roughly, and there was no evident change in the maximum discharge time for many years. The annual inhomogeneity of runoff distribution was reducing. The runoff concentration ratio was decreasing and both absolute and relative variation amplitudes were decreasing. In addition, the proportion of water quantity in non-flood season was somewhat increasing and the inter-annual distribution of runoff tended to uniform gradually.

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