Abstract: The interannual variation of river runoff in the Songhua River and Liaohe River basins was analyzed using the 40-year (1961-2000) observed monthly precipitation data from 132 meteorological stations and the 45-year (1956-2000) monthly observed runoff data from Harbin, Jiangqiao and Tieling hydrometric stations. The annual runoff in the region showed a weak decreasing trend in the Songhua River catchment, and a significant decreasing trend in the Liaohe River catchment. The consistent periodic variations of high/low water were found between the two river catchments. In the earlier 1980s, an abrupt change in summer runoff was detected, that is, a distinctive declining trend starting from the mid-late 1960s changed into an increasing trend in the earlier 1980s. The relationship between summer runoff and precipitation was discussed, and it was found that precipitation is one of the important climatic factors governing the variation of observed river runoff. Our study also reveals the possible impacts of human activities and land cover changes on surface runoff.

Key words: observed river runoff, trend, precipitation, Songhua River basin, Liaohe River basin