Analysis of multi-factors affecting sediment load in the Three Gorges Reservoir

Sediment inflow to the Three Gorges Reservoir (TGR) in the Changjiang decreased significantly, while little change was found in the runoff during the past two decades. The major reduction of sediment inflow occurred in one of the upper basins – the Jialingjiang Basin, which accounts for approximately 72.8% of the total reduction of 147 million t. The second major factor that contributes to this reduction occurred in two other upper basins, the Minjiang and Tuojiang, accounting for 17% of the total reduction. The remaining reduction occurred in other tributaries or reaches of the main stream, except in the Jinshajiang where the sediment inflow increased by 12 million t.The method adopted in this paper is a combination of typical study and genetic analysis. The analysis results show that the sediment discharge had decreased about 22 million t/a due to the variation of rainfall in the upstream of the TGR. In addition, 87.9 million t/a reduction of sediment occurred due to the construction of large and medium sized reservoirs, 24–29 million t/a sediment reduction occurred due to implementation of water and soil conservation measures; 64.6–69.6 million t/a of sediment reduction occurred due to sand excavation and sediment deposition. However, human activities such as road construction and mining resulted in an increase of sediment around 45 million t/a. The positive correlation observed between the analysis and the monitoring data shows the potential of applying the combined approach of hydrological statistical theory in predicting changing trends of sediment inflow in large rivers.