Abstract: The nonparametric Mann-Kendall method was used to detect the longterm trends and determine the significant level of annual runoff volume observed at the hydrological stations in mainstream basin of the Tumen River. The R/S analysis was applied to analyze the sustainability of annual, seasonal and monthly runoff volume, on which the Mann-Kendall test was used to examine the future trend of annual runoff volume. The results showed that there was generally a reduction trend of annual, seasonal and monthly runoff volume, the reduction of annual runoff volume was mainly caused by the reduction of runoff volume in spring and winter. The Hurst exponent indicated that the annual runoff volume was holistically decreased, and a continuous decrease may be maintained in the future. The sustainability of change trend of runoff volume was the highest in the upper reaches but the lowest in the lower reaches. The MannKendall change-point test method was used to determine the time series of hydrological change points of annual runoff volume. Results indicated that the hydrological change point occurred in 1985. At the same time, the annual precipitation in the mainstream basin of the Tumen River was also changed, so it was inferred that the decrease of precipitation may be an important factor resulting in a reduction of surface runoff volume in the mainstream basin of the Tumen River.

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