Human activities have more impacts on the recent discharge reduction of the largest tributary of the Yellow River relative to last three centuries.

How to quantitatively decouple the impacts of climate change and human activities on river discharge changes is a challenge in current global change research. As the largest tributary of the Yellow River (YR), the Weihe River (WR) is a typical river whose discharge is influenced by climate change and human activities. Here, we first attempt to obtain the normal-flow season and high-flow season discharge in the lower reaches of the WR by using tree rings and historical documents, respectively. The relationship between natural discharge in the two seasons is unstable and complex since 1678. Using an innovative method, we reconstructed the natural discharge from March to October (D), which explains >73 % of the variance in the observed D during the modeling period 1935-1970. There were 44 high-flow years, 6 extremely high-flow years, 48 low-flow years and 8 extremely low-flow years from 1678 to 2008. The contribution of WR annual discharge to the YR is 17 % over the past three centuries, and their natural discharge changes synchronously rise and fall. Human activities, such as the construction of reservoirs and check-dams, agricultural irrigation and domestic and industrial water consumption, have more impacts than climate change on the decrease in the observed discharge. In total, 53.5 % of the discharge reduction since 1971 is due to human activities, and 46.5 % is due to climate change. In addition, this study provides an important model for how to quantify the influences of human activities and nature on discharge reduction and to reconstruct seasonal resolution climate in global change studies.