Analysis of impacts of climate variability and human activity on streamflow for a river basin in northeast China

Hydrological processes in river systems have been changing under the impacts of both climate variability and human activities. The non-parametric Mann-Kendall statistic was used to identify change trends and points in the annual streamflow in the Hun-Tai River basin in northeast China. The identifications were based on streamflow records from six hydrological stations during 1961-2006, and the purpose was to analyze the change characteristics of the hydrological processes. The results indicated that all hydrological stations presented downward trends in annual streamflows. Abrupt changes in the annual streamflow occurred around 1978 in the Hun River basin, and around 1998 in the Taizi River basin. The impact of climate variability on the mean annual streamflow was also analyzed based on the relationships among streamflow, precipitation, and potential evapotranspiration. Precipitation and meteorological data from 22 rainfall stations and 10 weather stations within the basin were employed in the analysis. Daily potential evapotranspiration was calculated using the Penman-Monteith equation. Climate variability was estimated to account for 43% of the reduction in the annual streamflow, and human activities accounted for about 57%.