Based on daily streamflow data covering a 1960-2005 period, daily precipitation data during 1959-2013 period, together with data concerning crop areas and water reservoirs, thorough investigation is done on impacts of human activities (crop areas and water reservoirs in this study) and climatic changes (precipitation changes in this study) on hydrological processes of the Yellow River Basin. Differentiation is done on fractional contribution of climatic changes and human activities to changes in streamflow. The results indicate that percentiles of streamflow components of the Yellow River Basin are all in descending tendency and abrupt changes can be observed during mid and late 1980s and mid-1990s. The results of this study support the statement that precipitation plays the critical role in changes of streamflow across the Yellow River Basin. However, agricultural irrigation reflected by changes in crop areas can have different impacts on different streamflow components defined by different percentiles. Specifically, crop area changes have evident influences on streamflow magnitude and also variability of streamflow changes at the Huayuankou Station in the lower Yellow River Basin. Changes of climatic and crop indices are subject to minor variations but have apparent effects on magnitude of streamflow. For quantiles around the median, there is up to a 60% increment in the relation between streamflow and crop areas at the Tang Naihai Station. For the lower quantiles, there is up to a 40% reduction in the relation between streamflow and crop areas at the Toudaoguai Station. The results of this study are significant scientifically and practically in management of water resources and agricultural irrigation and also matter for enhancement of human knowledge concerning hydrological processes of the Yellow River Basin under the influences of human activities and climatic changes.