高海拔寒区融水土壤侵蚀机理与过程模拟研究

High erosion rate of seasonal frozen soils by snow-melting runoff in the high altitude and cold regions of China has great impacts on ecologic system， industries and people's lives of the localities. The regions under high erosion impacts in the high altitude and cold regions are selected to investigate snow-melting erosion of typical watersheds at different altitude and land covers. Heat transfer theories, with laboratory and field measurements are used to investigate the impacts of metrological factors and soil conditions on soil-melting and runoff generation as well as soil thermal properties. Automatic monitoring method is used to record the soil-melting process and runoff and sedimentation processes from hillslopes, gulley channels and small catchments, for understanding the soil mechanisms and obtaining the interactive relationship between runoff and erosion. Laboratory facilities will be made to control the soil frizzing and melting processes and to investigate soil erosion processes under different slope gradients, runoff rates and depths of melting soil layer so as to quantify the erosion rate of melting soil. Upon the understanding of the mechanisms and the determination of model parameters, model for soil melting and melting water runoff based heat transfer theory model is made to runoff and soil temperature processes. Hillslope, channel and watershed erosion models will be established and validated. The study aims to predict soil erosion under melt water runoff in the high altitude and cold areas so as to service the safety of ecological system and safe operation of facilities.

高海拔寒区季节性融水引起的水土流失严重，对生态及生产、生活和工程设施产生严重影响。项目选定高海拔寒区融水径流侵蚀强烈区域的典型流域，在不同海拔高程和下垫面条件下开展研究。采用室内外监测方法和热传导理论，研究气象要素与土壤热特性对融冻/水过程的影响机制，获得土壤热特性参数。采用水土流失自动监测方法，动态监测土壤融冻过程及土壤侵蚀过程，研究坡面、沟道和小流域土壤侵蚀产沙机理，获得融水产流产沙耦合关系。采用室内模拟方法控制土壤的冻结、解冻过程，研究不同坡度、流量、融冻土壤深度对融冻土壤侵蚀产沙过程的影响，确定融水径流的侵蚀产沙规律，认识融冻土壤侵蚀机理并获取模型参数。在上述研究的基础上，建立土壤融冻与融水过程的热力学模型，预测产流量与土壤温度变化过程；建立验证坡面产流、坡面侵蚀、沟道侵蚀、流域侵蚀预报模型。研究将实现高海拔寒区融水径流作用下水力侵蚀过程预报，为高海拔寒区生态、工程安全等提供基础。

本研究采用室内控制试验和野外多尺度冰雪融水补给流域现场监测相结合，开展了坡面和流域尺度的融水侵蚀过程机理、模型模拟及参数测量方法的研究。（1）侵蚀参数监测方法：发展可以替代烘干称重法精确测量土壤含水量的恒容容器方法；并据此提出了精确测量水体含沙量的体积置换方法。针对径流小区集流桶测量含沙量误差较大问题，提出误差校正的可能性。基于土壤入渗过程与细沟侵蚀过程的相似性，进一步发现测量和计算时间步长和计算数据放置点位，以同样方式影响入渗和侵蚀计算精度。因此，通过形式借鉴及理论融合，提出了改进土壤入渗率测量的建议；提出了通过采用细质地沙层或土层屏蔽大孔隙，测量得到土体基质入渗过程的方法，同时发展了测量土壤大孔隙流的方法。提出了电解质示踪测量薄层水流流速的脉冲边界法、实测边界法、虚拟边界法。创新性地用于测量冻土坡面、砾石层内、含碎石冻土和未冻土坡面、秸秆覆盖、饱和土壤表面水流流速。（2）融水侵蚀过程机理：设计了模拟土壤冻、融水侵蚀过程的设施、模拟方法与试验过程。提出了测量融冻土壤输沙能力的实验方法与程序，并揭示解冻深度对侵蚀过程的本质影响。输沙能力随解冻深度的减小而增大，小解冻深度时侵蚀输沙的变化趋势由一段随坡长增加的线性段和一段幂指数曲线组成。通过计算不同解冻深度的土壤剥蚀率，发现解冻土壤的剥蚀率和未冻土壤显著不同，由一段常数和一段随坡长和含沙量减小的过程组成；同时提出用土壤侵蚀剥蚀率为零时的含沙量确定水流输沙能力的方法，并用实验数据进行了验证。（3）融水侵蚀模型模拟：通过研究建立了土壤冻融过程模型、细沟侵蚀连续模型、融冻土壤侵蚀输沙能力模型、融冻土壤侵蚀过程模型、剥蚀速率模型、雅鲁藏布江流域融水侵蚀模型、区域冰川融水水土流失模拟模型。.发表论文SCI 22篇、EI 7篇、核心 2篇，发明专利 3个，专著 2部，软件著作权 1个，培养博士后 2名，博士 7名，硕士 16名。投稿待发表SCI论文5篇。.