Quantifying anthropogenic and climatic impacts on sediment load in the sediment-rich region of the Chinese Loess Plateau by coupling a hydrological model and ANN

The sediment load on the Chinese Loess Plateau has decreased sharply in recent years. Therefore, it is critical to determine the effects of anthropogenic and climatic factors on the reduction in sediment load. The Huangfuchuan River is the primary tributary in the sediment-rich region of the Loess Plateau in China. This study identified a significant reduction in the sediment load in the Huangfuchuan River basin. The accumulative anomaly method was used to determine the change in annual sediment load from 1960 to 2010. The mean annual sediment load in the Huangfuchuan River was 0.564 × 10⁸ t from 1960 to 1979 (Period I), and it decreased to 0.379 × 10⁸ t between 1980 and 1996 (Period II) and to 0.100 × 10⁸ t between 1997 and 2010 (Period III). Instead of conventional ways, a method that coupled a dynamic water balance model and a back-propagation artificial neural network was employed to separate the contributions of climate variability and human activities on the reduction in sediment load. The results showed that compared to the sediment load in Period I, human activities were responsible for 64.32 and 71.55% of the reductions in sediment load in Periods II and III, respectively, while climatic effects accounted for 35.68 and 28.45% of the reductions in Periods II and III, respectively. The construction of check dams was the main human activity that resulted in the sediment reduction between Periods I and II and accounted for 35.51% of the decrease. Vegetation restoration due to the implementation of the “Grain-to-Green” program was the dominant cause of the reduction in sediment between Periods II and III and caused more than 40.00% of the decrease. The increase of water consumption by humans also contributed the reduction in sediment between Periods II and III in the Huangfuchuan River basin.