The effects of climate change and human activities on the evolution of hydrological drought in the upper watershed of Hutuo River

Based on the monthly runoff data and daily meteorological data of the upper reaches of Hutuo River from 1961 to 2018, the ABCD hydrological model and GAMLSS model with time as explanatory variable were constructed to calculate the time-varying standardized runoff index. On the basis of comprehensive consideration of change point analysis, climate change and different stages of social development, the study time domain was divided into three phases: natural period (1961-1979), first impact period (1980-1997) and second impact period (1998-2018). Then, based on the linear rate of change of drought index with respect to time, the influence of climate change and human activities on the evolution of non-stationary hydrological drought under changing environment were quantified. The following results are obtained: At the seasonal and annual scales of the two influence periods, the trend of non-stationary hydrological drought was all alleviated; In the first impact period, climate change and human activities mainly alleviated hydrological drought at both seasonal and annual scales, but human activities dominated the contribution rate of 53.22% to 89.11%; At the seasonal and annual scales of the second influence period, the main factor of hydrological drought mitigation was climate change, which contributed 50.72% to 72.68%. However, hydrological drought was exacerbated by human activities, which contributed between −49.27% and −27.32%; In the second influence period, the drought index series caused by human activities and climate change showed a significant negative correlation at both 3-month scale and 12-month scale, which indicates that after entering the 21st century, people's intervention in the water cycle is more scientific and rational than that in the 20th century.