澜沧江源区历史径流泥沙序列重构研究

The research on runoff and sediment runoff in source area of Lancang River is deficient, which makes the research on the adaptability utilization of its runoff and the transfer of biogenic matters suffer bottleneck. We takes the head of Lancang River as the research object, and uses paleaoflood hydrology and river dynamics to study digital restoration of historic morphology, the reconstruction of the long-term runoff sediment data and the sequence. Firstly, the paleaoflood level and the ancient channel morphology of Nangqian reach several sections in Lancang River will be studied with the slack-water deposit（SWD） and dating technique. Besides, 1D numerical model of water and sediments about historical channel is constructed, so as to obtain the paleaoflood discharge and the bank-full discharge about different ages in the past 10,000 years. To study the quantitative relationship between bank-full discharge and annual runoff, as well as the quantitative relationship between sediment discharge and sediment runoff in order to obtain the annual runoff and sediment runoff at some representative years; Based on the actual observed water and sediments data, we can reconstructs the sequence of long-term runoff and sediment runoff with fractal interpolation model, and analyzes its multi-scale characteristics, and then proposes the method for the reconstruction of historical runoff data and the sequence. The study correspond to the requirement for major research plans and cultivation projects, and the expected results will enrich the paleaoflood hydrology and river dynamics, which could provide science support for the adaptability utilization of runoff in Lancang River and the research on the transfer of biogenic matters, and provide theoretical references for the sequence reconstruction of runoff in other river source areas in the Southwest China.

澜沧江源区径流泥沙相关研究匮乏，成为了其径流适应性利用和生源物质迁移研究的瓶颈。本项目以澜沧江源区河段为研究对象，采用古洪水水文学和河流动力学方法，对其河流历史形态数字复原和长时期径流泥沙数据重建与序列重构进行研究。首先通过平流沉积法和测年技术，进行澜沧江囊谦河段多断面洪水位判定及古河道断面形态复原，并构建各年代古河道水沙数学模型，得出万年以来代表性年代的古洪水流量和平滩流量；研究平滩流量与年径流量、平滩流量下输沙率与年输沙量的定量关系，得到代表性年代年径流量和输沙量；结合现有实测水沙数据，采用分形模型对其长时期径流泥沙序列进行重构，分析其多尺度特征，综合提出河流历史径流泥沙数据重建和序列重构方法。本研究契合重大研究计划培育项目支持方向的要求，预期成果将丰富古洪水水文学和河流动力学学科，为澜沧江径流适应性利用和生源物质迁移研究提供科学支撑、为其他西南河流源区径流泥沙序列重构提供理论参考。

项目针对澜沧江源典型河段历史形态变化、历史时期输水输沙能力变化及其序列重构开展研究。按照资助计划书安排，项目主要开展了以下工作。.（1）数据层面：开展了科学界首次在澜沧江源的河流横断面沉积物钻孔取样和滞洪沉积物工作，得到了6个断面、35个钻孔、223组河床沉积物样品和15处共计32个洪水沉积物样品，测试了其级配和部分样品的年代。.（2）方法层面：提出了河流历史形态数字复原方法和砂卵石河床组成的冲积河流糙率估算方法，丰富了河流动力学学科，为资料贫乏地区河流历史演变调查提供了新的方法。.（3）实测资料分析成果：通过近年影像、实测地形图、水位流量关系等分析，认为澜沧江源囊谦河段尽管形态复杂、汊道交织，但年际间总体河势是稳定的；基于沉积物粒度分析得出了澜沧江源囊谦河段的河流沉积环境特征，认为其河段为典型壅水沉积河段；粒径沿横断面分布表现为河槽沉积物粒径较粗、边滩及江心滩粒径较细，其堆积速率相对较快，加之洲滩植被发育、促淤能力更强，河段确定为稳定的多股分汊河型。.（4）数据重建研究成果：依据河床沉积物分层年代测试结果，复原得到了典型断面的历史形态，即0.7ka、2ka和7ka3个时期的概化形态，复原得到的断面年代多为历史暖期、其输水输沙能力更强，其中0.7ka的平滩面积约为当前断面的1.28倍，2ka时期的平滩面积约为当前的1.9倍。考虑各年代的床沙级配变化得到0.7ka和2ka河段糙率分别为0.039和0.042；根据连续滞洪沉积物高程得到其历史洪水的水面比降为0.002；在此基础上，重建出0.7ka和2ka的河道平滩流量，分别约为当前河道平滩流量的1.5倍和2.7倍。.项目组共享了收集、采集的数据资料，重建了澜沧江有源区的历史径流，为河流径流泥沙序列重构提供了新的方法。成果可深化对长时期气候变化下河流系统响应的科学认识，有助于解决本重大研究计划核心科学问题之一“气候变化驱动下的下垫面变化及其径流效应”。