Quantitative estimation on contributions of climate changes and human activities to decreasing runoff in Weihe River Basin, China

Human activities and climate changes are deemed to be two primary driving factors influencing the changes of hydrological processes, and quantitatively separating their influences on runoff changes will be of great significance to regional water resources planning and management. In this study, the impact of climate changes and human activities was initially qualitatively distinguished through a coupled water and energy budgets analysis, and then this effect was further separated by means of a quantitative estimation based on hydrological sensitivity analysis. The results show that: 1) precipitation, wind speed, potential evapotranspiration and runoff have a significantly decreasing trend, while temperature has a remarkably increasing tendency in the Weihe River Basin, China; 2) the major driving factor on runoff decrease in the 1970s and 1990s in the basin is climate changes compared with that in the baseline 1960s, while that in the 1980s and 2000s is human activities. Compared with the results based on Variable Infiltration Capacity (VIC) model, the contributions calculated in this study have certain reliability. The results are of great significance to local water resources planning and management.