Long term streamflow trends in the middle reaches of the Yellow River Basin: detecting drivers of change
x; " The catchments in the Loess Plateau, in China s middle reaches of the Yellow River Basin, experienced unprecedented land use changes in the last 50 years as a result of large scale soil conservation measure to control soil erosion. The climate of the region also exhibited some levels of change with decreased precipitation and increased temperature. This study combined the time trend analysis method with a sensitivity based approach and found that annual stream fl ow in the Loess Plateau decreased signi fi cantly since the 1950s and surface runoff trends appear to dominate the stream fl ow trends in most of the catchments. Annual base fl ow exhibited mostly downward trends, but signi fi cant upward trends were also observed in 3 out of 38 gauging stations. Mean annual stream fl ow during 1979 2010 decreased by up to 65% across the catchments compared with the period of 1957 1978, indicating signi fi cant changes in the hydrological regime of the Loess Plateau. It is estimated that 70% of the stream fl ow reduction can be attributed to land use change, while the remaining 30% is associated with climate variability. Land use change because of the soil conservation measures and reduction in precipitation are the key drivers for the observed stream fl ow trends. These fi ndings are consistent with results of previous studies for the region and appear to be reasonable given the accelerated level of the soil conservation measures implemented since the late 1970s. Changes in sea surface temperature in the Paci fi c Ocean, as indicated by variations in El Nino Southern Oscillation and phase shifts of the Paci fi c Decadal Oscillation, appear to have also affected the annual stream fl ow trends. The framework described in this study shows promising results for quantifying the effects of land use change and climate variability on mean annual stream fl ow of catchments within the Loess Plateau.