Impact of Human Activities on Hydrological Drought Evolution in the Xilin River Basin

The impact of human activities on the hydrological cycle makes hydrological drought no longer a natural disaster in a strict sense, and influences the stationarity of the hydrologic process. In this context, assessment methods that consider nonstationary conditions are more reasonable in the study of hydrological drought. In this study, we used the SWAT (Soil and Water Assessment Tool) model to reconstruct the historical hydrological conditions during the period affected by human activities (1998–2019) of the Xilin River Basin. After calculating the standardized runoff index (SRI) at multiple time scales, we compared the drought characteristics of the basin under natural conditions and under the influence of human activities. The results show that human activities were the main reason for the significant decrease of runoff in the basin (an obvious change-point for runoff series is identified in 1998), which accounted for 68%. Compared with natural conditions, human activities delayed the occurrence of short-term drought in the basin and changed its seasonal distribution characteristics, resulting in an increase in the frequency of severe and extreme droughts in autumn; the corresponding drought frequency increased by 15% and 60%, respectively. Moreover, human activities have also prolonged drought duration, increased drought intensity, and increased the uncertainty of drought in the basin. The proposed method is demonstrated to be efficient in quantifying the effects of human activities on hydrological drought, and the findings of this study provide a scientific basis for water resource management, drought early warning, and forecasting under a changing environment.