青海北川河流域径流变化的机理研究——基于模型和统计两种方法

Investigating the mechanisms of streamflow change in the Beichuan River Basin,Qinghai Province:Based on modeling and statistic analyses

气候变化和下垫面变化是影响河道径流的两大驱动力,研究两者对径流的影响有利于深入理解流域水文过程,为水资源管理提供科学依据。鉴于利用不同方法获得的结果存在一定程度的差异,有必要使用多种方法进行交叉验证。论文基于Budyko水量平衡法和新增水库模块的分布式水文模型(DHSVM)法量化了气候变化和下垫面变化对青海省北川河流域径流变化的贡献。结果表明:(1)自1960年以来流域出口流量以每年0.037 m3/s的趋势下降,突变年份发生在1969年。(2)2种方法的分析结果均表明,年代际尺度上,气候变化对径流影响的贡献率由高到低依次为:1990—1999年>2000—2009年>1970—1979年>1980—1989年=2010—2019年,且下垫面变化是1970—2019年流域出口径流变化的主导因素,对应的贡献率分别为94.58%(Budyko法)和65.68%(DHSVM法)。(3)Budyko方法只能揭示流域整体的变化,而DHSVM方法能够体现水文过程变化的时空差异,模型结果表明上中游、下游地区的年平均径流变化分别受气候变化、下垫面变化主导;流域出口处月径流变化则对下垫面条件中的水库调节更敏感。此外,文中就2种方法量化结果差异的原因也展开了讨论。

Climate change and land use/cover change(LUCC)are two major drivers that impact streamflow.Deconvolving the impacts of climate change and LUCC on streamflow will benefit local water resources management.In this study,two methods—the Budyko water balance method and the Distributed-HydrologySoil-Vegetation Model(DHSVM)coupled with a new reservoir regulation scheme—were used to deconvolve the impacts of climate change and LUCC on the streamflow in the Beichuan River Basin,Qinghai Province,to reduce uncertainty in the results inherited from the individual methods through cross examination.The study found that:1)Streamflow at the basin outlet decreased at 0.037 m3/s per year in 1967-2019,and the abrupt change occurred in 1969.2)Both methods agree that the relative impacts of the decadal climate change during the past five decades were in the order of 1990 s>2000 s>1970 s>1980 s=2010 s,and LUCC was the dominant driver for streamflow reduction at the outlet for 1970-2019,with 94.58%and 65.68%contributions for the Budyko method and the DHSVM,respectively.3)The Budyko method specializes in assessing the change of the entire river basin,while the distributed hydrologic modeling can efficiently describe the spatiotemporal heterogeneity of the impacts across the basin.The modeling showed that streamflow changes in the upstream and midstream was dominated by climate change,but downstream flow change was controlled by LUCC.Reservoir regulation exerted important impact on monthly streamflow.The possible reasons of the discrepancies in climate change and LUCC impacts estimated by the two methods were also discussed.