Effects of large-scale climate patterns and human activities on hydrological drought: a case study in the Luanhe River basin, China

Evaluation of the impact of climate variability and human activities on hydrological drought is of great significance for drought mitigation strategies. In this study, standardized runoff index (SRI) at various time scales is used to characterize hydrological droughts in the Luanhe River basin, northeast of China, for the period of 1959-2011. Correlation analysis is conducted to examine the associations between the hydrological droughts and large-scale oceanic-atmospheric patterns (AMO and ENSO). Climate-induced and human-induced influence indices are also developed based on standardized precipitation index and SRI to investigate the possible influences of the climate patterns and human activities on the hydrological droughts. Results indicate that the significant influence of AMO on hydrological drought at different time scales is evident among different months across the Luanhe River basin, with warm (cold) AMO phases favoring drought (wet) conditions. The direct linkage of ENSO to hydrological drought is relatively weak in the basin, while the extent of the linkage can be improved with increasing time lags. Moreover, El Nio phases show a closer relation with the drought events of the region as compared with La Nia phases. It is also implied that human activities exhibit aggravating effects on hydrological drought at shorter time scales over the basin, whereas they might show mitigating effects at longer time scales in some areas of the basin. These findings can be beneficial for better understanding how the hydrological drought responses to climate changes and human activities, thereby providing valuable references for drought forecasts and water resources managements in the Luanhe River basin.