Dynamic evolution characteristics of the Yellow River Delta in response to estuary diversion and a water-sediment regulation scheme

River deltas have received increasing attention over the past 50 years due to their socioeconomic importance and unique ecology. In this study, long-term hydrological data and remotely sensed satellite images were used to analyze the influence of estuary diversion and a water-sediment regulation scheme (WSRS) on the Yellow River Delta. The results show that the evolution of the delta's area since the 1980s can be divided into three stages: a rapid accretion stage (1985-1996), a retreat stage (1997-2001) and a recovery stage (2002-2020). The efficiency of sediment feeding the delta through the Qing 8 course during 1997-2020 (24.05 km2 (109 t)-1) was slightly lower than that through the Qingshuigou course during 1985-1995 (25.63 km2 (109 t)-1). For the old Qingshuigou lobe and the new Qing 8 lobe, critical sediment demands are estimated to be 303.9 x 106 t and 44.1 x 106 t per year, respectively, to maintain area equilibrium. The distribution of sediment sources for the delta's growth have changed due to the implementation of the WSRS: the fraction of annual average net sediment flux from the river's middle reach decreased from 87.1 % to 43.5 %, while that from the lower reach increased from zero to 19.7 %.