Separating the impacts of climate variability,land-use change and large reservoir operations on streamflow in the Yangtze River basin,China,using a hydrological modeling approach

Separating the individual effects of climate variability and human activities on streamflow is more important than just knowing their combined effects.In this paper,using a scenario-based hydrological simulation approach,the streamflow changes caused by climate variability and two different types of human activities(i.e.land-use change and large reservoirs operations)as well as the contribution rates of these three factors over 272 sub-basins in the Yangtze river basin were quantified and compared among 5 different periods(i.e.1988–1992(P1),1993–1997(P2),1998–2002(P3),2003–2007(P4)and 2008–2012(P5)).Results demonstrate that,at the annual scale,climate variability played a leading role in the change in outflow of most sub-basins.With regard to the seasonal variations in discharge at Datong station,climate factors played a predominant role during P1-P2 and P2-P3.Since the Three Gorges Reservoir began operating in 2003,the discharge was enhanced by reservoirs in January-May and reduced by reservoirs in JulyDecember.Reservoir and climate factors codetermined seasonal streamflow change during P3-P4 and P4-P5.Land-use change made the smallest contribution to seasonal discharge fluctuations.This study can support decision-making in regional water resources planning and management.