Propagation from meteorological drought to hydrological drought under the impact of human activities: A case study in northern China

Meteorological drought is a precursor of hydrological drought. Understanding the propagation from meteorological drought to hydrological drought is important for the early warning of hydrological drought. This study investigated this drought propagation by analyzing the correlation between the Standardized Precipitation Index (SPI) (a metric of meteorological drought) and Standardized Runoff Index (SRI) (a metric of hydrological drought), over the upstream, midstream and downstream areas of the Luanhe River Basin (LRB). Results revealed little difference in meteorological drought characteristics between pre- and post-human disturbance period, while hydrological drought became more frequent In the pre-human disturbance period, the drought propagation was mainly affected by catchment characteristics. The time of propagation of meteorological drought to hydrological drought was shorter in grassland dominated subbasin (1-5 months) than in forest dominated subbasin (4-7 months) in rainy season. The drought propagation in these two subbasins showed a similar lag time of 7-12 months, when it comes to dry season. Under the influence of changing environments and agricultural activities in upstream area, drought propagation prolonged from 4-9 months to 5-12 months during December through June. In the downstream area, the drought propagation time during October through April becomes 1-2 month shorter, which is likely caused by the increase in the domestic water supply and the expansion of the urban area. Results of this study will be helpful for the development of improved drought warning and forecasting system in arid and semi-arid areas.