气候变化和人类活动对鸭绿江流域入海水沙通量的影响

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

为探讨气候变化、人类活动(植被变化和水库修建活动)对入海水沙变化的影响,运用HydroTrend3.0.4水文模型,对1958—2012年,3种情景模式(气候变化、人类活动以及气候变化和人类活动共同驱动下)鸭绿江流域的入海水沙进行模拟,定量估算出流域气候变化和人类活动对入海水沙通量的影响。研究表明1958—2012年间气候变化驱动、人类活动驱动以及两者共同作用的流域年入海径流量分别为264.5×10~8、264.3×10~8和263.7×10~8 m^3/a,年入海输沙量达到5.53、1.62和1.59Mt/a,而流域多年实测入海径流量与输沙量分别为259.2×10~8 m^3/a和1.48Mt/a。气候变化驱动下,不同年际间的降雨量变化(即暴雨和干旱的频率和强度)是导致鸭绿江流域年均入海径流量变化的最主要原因,而频发的山洪是年均入海输沙量变化的主导因素。气候与人类活动共同作用下,流域不断加剧的人类活动成为鸭绿江流域年入海输沙量变化的主导因素。流域人类活动对入海输沙量变化的贡献量为3.94Mt/a,其中流域植被变化导致水土流失量增加1.20Mt/a,而流域大坝拦截了5.14Mt/a的入海沉积物,76.4%的入海沉积物被鸭绿江流域的梯级水库所拦截。因此,估算1940年鸭绿江流域修建水库前,其入海输沙量达到6.73Mt/a,约为现在鸭绿江入海输沙量的5倍。

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 264.5×10~8 m^3/a,264.3×10~8 m^3/a and 263.7×10~8 m^3/a,and sediment load was5.53 Mt/a,1.62 Mt/a and 1.59 Mt/a,respectively.The observed water discharge and sediment load were 259.2×10~8 m^3/a and 1.48 Mt/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 3.94 Mt/a,including an increase in 1.2 Mt/a sediment yielding by water and soil erosion,and a larger decrease in 5.14 Mt/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 6.67 Mt/a,5 times of the present sediment load into the sea.