黄土高原典型流域输沙量变化及减沙贡献率分析

Contribution rates of sediment transport variation in typical watersheds in the Loess Plateau

定量研究气候变化和人类活动的减沙贡献率,可为流域生态治理目标与措施精准布局提供科学依据。针对黄土高原无定河流域及其支流大理河流域,综合利用双累积曲线法、淤地坝减沙模型、Gamlss模型减沙贡献率分析法,开展一般降雨和极端降雨条件下减沙贡献率定量测算和水土保持措施的减沙效益分析。结果表明1960-2015年大理河输沙量以1960-1970年、1971-2002年和2003-2015年三个阶段呈现趋势性减少。人类活动是输沙量减少的主要原因。1971-2002年,沟道措施是主要减沙措施,占水土保持措施减沙量比例约为58%;2003-2015年,坡面措施为主要减沙措施,占水土保持措施减沙量比例约为67%,其中梯田30%,林草37%。水土保持措施在极端降雨条件下能够有效减少输沙量。相似极端降雨情景下,2017年无定河流域次洪输沙量较1977年减少53%。

Quantitative analysis of the contribution of climate changes and human activities on sediment reduction rate can not only provide scientific basis for ecological management target,but also help to precise layout of soil and water conservation measures.The contributions of climate and human factors on sediment reduction of Wuding River with the tributary Dali River basin in the Loess Plateau under normal and extreme rainfall conditions were analyzed by the double mass curve,silt dam sediment reduction model and the Gamlss-based.Results show that:(1)The sediment discharge of Dali River during 1960-2015 showed a decrease trend in1960-1970,1971-2002 and 2003-2015.(2)Human activities are the main factor to decrease sediment discharge in the Dali River Basin.During 1971-2002,gully measures were the main sediment reduction measures,accounting for approximately 58%of the sediment reduction of water conservation measures;in contrast,during 2003-2015,slope measures were the main sediment reduction measures,accounting for approximately67%by silt dam sediment reduction model and 78%by the Gamlss-based.(3)Soil and water conservation measures can effectively reduce sediment transport under extreme rainfall conditions.Under the same extreme rainfall conditions,the sediment discharge decreased by 53%in 2017 compared with in 1977.