Variations in water discharge and sediment load in the Yalu River catchment induced by human activities and climate changes

In order to reveal the influence factors dominating the water input and sediment discharge into the sea from the Yalu River catchment, the numerical model of HydroTrend3.0.4 with three scenarios, i.e. the climate change-driven, Human activities-driven, and combined climate change and human activities-driven senarios, is adopted to simulate water and sediment fluxes into coastal coastal ocean during the period of 1958-2012 at two river gauging stations. Results indicate that, during the period, water discharge of climate change-driven, Human activities-driven, and combined climate change and human activities-driven scenarios were 264.5×10⁸ m³/a, 264.3×10⁸ m³/a and 263.7×10⁸ m³/a, and sediment load was 5.53Mt/a, 1.62Mt/a and 1.59Mt/a, respectively. The observed water discharge and sediment load were 259.2×10⁸m³/a and 1.48Mt/a. Under the scenario driven by climate change, the main factor dominating the variation of water discharge is precipitation, and the sediment flux variation under natural condition is mainly controlled by frequent flood events during the wet season. However, under the scenario of the combined climate change and human activities-driven, the intensifying human activities have caused dramatic change in sediment load into the sea: the anthropogenic impact can totally decrease the sediment flux of the Yalu River by 3.94Mt/a, including an increase in 1.2Mt/a sediment yielding by water and soil erosion, and a larger decrease in 5.14Mt/a by the dam interception effect. We also found that the sediment load entering the sea of the Yalu River before 1940 (pre-dams) was about 6.67Mt/a, 5 times of the present sediment load into the sea.