黄河上游十大孔兑流域泥沙输移过程及机制研究

Riverine sediment erosion, transport, deposition is an important land surface process. It has impacted on many aspects of human life and production. The Ten Great Gullies are some of the main tributaries in the upper Yellow River with a large sediment yield. Their sediment outputs have played a great role in the changes of sedimentation in the channel of Inner-Mongolian reach of the Yellow River. Using runoff and sediment load records and data of relevant natural factors and land use, studies will be done on the processes of runoff and sediment transport, relations of water flow and sediment transport on different temporal scales, the influence of aeolian-fluvial interactions on sediment yield of the rivers, and the causes for their changes. Field investigations and surveys will be carried out to find out the changes in store and release of sediment in gullies and channels, the relations of store and release of sediment with influencing factors, the contribution of sand from desert to sediment yield of the Gullies and their relations with meteorological factors, the thresholds for the changes between sediment store and release, and the impacts of store and release of sediment in gullies and channels on changes in sediment load of the Gullies. By drilling cores, the deposit texture and structure of the fluvial fans in the lower reaches of the Gullies will be explored, and the changes of sediment storage in the fans as a principal sediment sinks of the Gullies, the main factors for the changes, and the influence of sediment storage in the fans on sediment output of the Gullies will be analyzed. Finally, the structure and function of the sediment routing systems of the Gullies will investigated holistically in order to disclose the changes in sediment connectivity and causes and build relations of sediment outputs from the Gullies with the influencing factors. It is anticipated that the results of the project will contribute to the theory of riverine sediment routing system and reinforce the scientific basis for soil erosion control in the Ten Great Gullies themselves and alleviation of channel aggradation of the Inner-Mongolian reach of the Yellow River.

流域泥沙侵蚀、搬运和沉积是重要地表过程，它给人类生产和生活带来多方面的影响。十大孔兑是黄河上游重要产沙支流，对黄河内蒙段河道冲淤演变影响较大。本项目将利用水文泥沙观测数据和相关自然要素及土地利用资料，分析流域产流产沙的过程、不同时间尺度流域水沙关系、风水交互作用对流域产输沙的影响及其原因。野外调查测量沟道与河道泥沙存储与释放，分析沟道泥沙存储量变化与影响因子的关系、沙漠风沙对河流泥沙的贡献量及其与气候因子的关系、研究泥沙存储与释放临界条件以及泥沙存储与释放对流域输沙变化的影响。钻探分析孔兑下游冲积扇沉积结构和构造，研究其作为流域主要泥沙汇泥沙存储量的变化及其与主要影响因素关系和对孔兑入黄泥沙量的影响。最终从整体上分析揭示孔兑流域泥沙输移系统的结构和功能，掌握流域输沙连通性变化及其原因，构建流域输沙与影响因子关系模型。将为流域输沙系统理论发展，孔兑土壤侵蚀以及黄河内蒙段河道治理提供科学支撑。

流域泥沙侵蚀、搬运和沉积是重要地表过程，它给人类生产和生活带来多方面的影响。十大孔兑是黄河上游重要产沙支流，对黄河内蒙段河道冲淤演变影响较大。利用典型孔兑流域水文泥沙观测数据和相关自然要素及土地利用资料，对流域径流输沙变化与原因进行了深入研究；开展典型沟道和河岸沙丘地形重复测量，结合遥感影像解译，分析了流域上中游泥沙存储与释放过程；通过钻探和沉积物采样分析，研究了流域泥沙来源和沿河河床及下游冲积扇泥沙沉积过程；综合分析流域自然地理条件、地质地貌特征、沉积物组成和流域输沙数据，探讨了孔兑流域输沙系统特征以及流域输沙与影响因子的关系。研究揭示孔兑以沟道产沙为主、以沟道中高含沙水流侵蚀输沙控制流域产沙，发现高含沙洪水频率减少造成了近期典型孔兑产沙量显著减小，定量分析得出了气候变化和人类活动对典型流域产水产沙变化的贡献，研究成果对正确认识流域水沙变化原因和对制定水土保持规划有参考价值。研究揭示了孔兑流域水系及地貌特征、地貌演化趋势及其对流域输沙长期变化的影响，建立了孔兑输沙量与沟壑密度及水系分维数的关系，为预测未来流域自然产沙变化趋势提供了依据。定量估算了沙漠沙入河量，发现其存在年内和年际间存储与释放现象，提高了风水交互侵蚀作用过程的认识，对规划流域治理重点有较大的参考价值。采样和探地雷达探地获得了十大孔兑从河道到冲积扇大量地表和地下泥沙沉积物数据，揭示了孔兑泥沙沉积物组成和结构特征、沉积过程、沉积环境及物源，发现孔兑冲积扇以垂向加积为主，且沉积之后很少受到水力侵蚀破坏和风力作用的改造。发现孔兑产沙在冲积扇堆积的比例不大，大部分输入了黄河，成果有助于深入了解长时间孔兑输沙入黄变化及其对黄河内蒙段淤积的影响。定量研究了黄河宁蒙段冲淤和河床形态变化过程与原因，发现十大孔兑来沙变化几乎在内蒙河段引起等量的冲淤变化量，研究成果对黄河上游流域整治和利用水库进行水沙调节有较大的参考价值。