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• The rainfall-runoff relationship has changed under climate change and human activities in the TRH region. • The impacts climate indicators of rainfall-runoff ratio in the sub-basins of TRH region were different. • The contribution rates of human activity in the YRB were a little higher than that in the YARB. Identifying the impact of climate change and human activities on rainfall-runoff relationship in the Three-River Headwaters (TRH) region is essential for water source conservation, ecological security, and biodiversity maintenance of China and East Asia. In this paper, the runoff-rainfall ratio was used as the index of rainfall-runoff relationship. Different methods were employed to identify the impact indicators and quantitative assessment of rainfall-runoff relationship from 1957 to 2016. The results are the following: (1) the rainfall-runoff relationship has changed in the source regions of Yangtze River basin (YARB) and Yellow River (YRB), and runoff-rainfall ratio has increased by 2.9% and decreased by 3.2%, respectively; (2) the main climate indicators of runoff-rainfall ratio were rainfall, potential evaporation and sunshine hours in the YARB, and rainfall, potential evaporation and temperature in the YRB; (3) the contribution rates of human activity in the YRB were a little higher than that in the YARB, and the contribution rates of climate change and human activity were 90.9% and 9.1% in the YARB and 42.9% and 57.1% in the YRB. The results can provide invaluable information for managing water resources and taking ecological protection measures. [ABSTRACT FROM AUTHOR]

The Weihe River Basin (WRB) in a monsoon transition zone of East Asia interacts with multiple weather systems and is susceptible to floods and droughts. We developed a framework based on the Empirical Orthogonal Function analysis, Complete Ensemble Empirical Mode Decomposition with Adaptive Noise analysis, and moving-average based Spearman rank correlation to identify the spatial patterns of the dry/wet conditions from 1470 to 2016, decompose the dry/wet index into the leading components with a period between 2 and 3 years and 100+ years, and discover their driving forces on multiple time scales. Results show that WRB can be divided into four distinguishable hydroclimatic subregions located in the southeast, west, central, and north. The East Asian summer monsoon and South Asian summer monsoon impact this region mainly on the inter-annual and inter-decadal scales, while the impacts of ENSO, PDO, AO, and NAO are dominant on the multi-decadal and centennial scales. [Display omitted] • Developed a new framework to attribute dry/wet spatiotemporal variability on multiple time scales. • Revealed four unique hydroclimatic subregions for the Weihe River Basin. • Identified the effects of monsoons, plateau circulation, westerly, and solar activities on Weihe. • Dry/wet conditions of the subregions show opposite responses to solar activity. [ABSTRACT FROM AUTHOR]