Published in Hydrological Processes
Separating climate change and human contributions to variations in streamflow and its components using eight time‐trend methods
Ling Zhang, Zhuotong Nan, Weizhen Wang, et al.
Separating impacts of human activities and climate change on hydrology is essential for watershed and ecosystem management. Many previous studies have focused on the impacts on total streamflow, however, with little attentions paid to its components (i.e., baseflow and surface runoff). This study distinguished the contributions of climate change and human activities to the variations in streamflow, baseflow and surface runoff in the upstream area of the Heihe River Basin, a typical inland river basin in northwest China, by using eight different forms of time‐trend methods. The isolated contributions to streamflow variation were also compared with those obtained by two Budyko‐based approaches. Our results showed that the time‐trend methods consistently estimated positive contributions of climate variability and human activities to the increases in streamflow and its components, but with obviously varying magnitudes. With regarding to streamflow, the time‐trend method DMC‐Wei, with a physical basis, produced a reasonable smaller contribution of human activities than climate changes, in consistent with the Budyko‐based approaches. However, all the other time‐trend methods led to contrary results. The contributions to baseflow variation diverged more significantly than those to streamflow and surface runoff, ranging 24‐92% for human activities and 8‐76% for climate variability. In terms of surface runoff, most of the time‐trend approaches produced smaller contributions of human activities (ranging 21‐49%) than climate change. The uncertainties associated with the various time‐trend approaches and the baseflow separation algorithm were revealed and discussed, along with some recommendations for future work.