东江流域水沙变化定量归因及对河道冲淤影响研究

Quantitative Attribution of Runoff and Sediment Changes in the East River Basin and Impact on Erosion and Siltation of River Channel

在全球气候变暖和强人类活动干扰下,流域水沙发生显著变化,影响了河流、河口和近海的生态环境。以东江流域为研究对象,应用M-K和Pettitt检验分析水沙变化特征,通过双累积曲线法和改进的变化归因分析水文模拟法定量分离了气候变化和人类活动对流域水沙的影响,并进一步揭示了其对河道冲淤的影响。结果表明:①SWAT模型适用于东江流域日和月尺度水沙模拟,对日均流量高于1500 m^3/s的径流泥沙模拟较低;②径流和泥沙变异点分别为1973、1988年,因此,设定径流基准期为1967—1973年,泥沙基准期为1967—1988年,影响期均为2009—2016年;③人类活动对流域水沙变化的影响不可忽视,影响期气候变化与人类活动对流域径流贡献率相似,分别为57%和43%,气候变化和人口增长是导致径流减少的主要原因,而以建坝为主的人类活动对泥沙的贡献率高于90%,人口增长、水土保持工程及大坝建设是流域泥沙减少的主要因素;④受河道采砂影响,基准期后以建坝为主的人类活动对中下游河道影响先减小后增大,影响期建坝因素对河道中下游的冲淤贡献为25.8%,不是中下游河道演变的主要因素。

Under the disturbance of global warming and intensive human activities,runoff and sediment in the river basin have changed significantly,thus causing enormous ecological and environmental pressure in rivers,estuaries and coastal waters.Taking East River basin as the research object,this paper analyzes the temporal characteristics of runoff and sediment by M-K test and Pettitt test,quantitatively separates the impact of climate change and human activities on runoff and sediment in the river basin by the double mass curve method and modified SWAT model,and evaluates its effect on erosion and siltation of downstream river channel.Results show that:①SWAT model was suitable for the daily and monthly runoff and sediment simulations in the East River basin,with poor simulation for runoff and sediment with daily average discharges higher than 1500 m^3/s;②The change point of runoff and sediment was 1973 and 1988 respectively.Therefore,the baseline period for runoff was 1967—1973 and sediment was 1967—1988,while impact period was 2009—2016;③The impact of human activities on water and sediment changes in the basin is significant.Contribution of climate change and human activities for runoff in 2009—2016 was about 57%and 43%respectively.Climate change and population growth were the main contribution factors for annual runoff reduction.While human activities,especially dam construction,contributed over 90%of sediment.Population growth,soil and water conservation project,and dam construction in basin were the major factors for annual sediment reduction;④Affected by sand mining in river channel,after the baseline period,the impact of human activities,especially dam construction on the middle and lower channel was firstly decreased and then increased.During the impact period,the contribution of dam construction to the erosion and siltation of middle and lower river channel was 25.8%,which was not the main factor for the evolution of the middle and lower river channel.