高寒山区季节性土壤冻融对径流过程的影响---以巩乃斯河流域为例

The rivers in arid area of northwest China originate from mountains with high elevation and low temperature. The influence of soil freezing-thaw on streamflow in alpine watershed is an important research project. This study tries to analyze the seasonal soil freezing-thaw regime through a coupled model of soil water and heat, and explore the influence of soil freezing-thaw process on streamflow through modifying the snowmelt-runoff model. The modified snowmelt-runoff model combines the coupled model of soil water and heat and hydrological model based on System Dynamic principles. In this study, the discipline of the seasonal soil freezing-thaw process and the relationship between surface runoff and rainfall and snowmelt water are going to be analyzed by designing field experiments in Banchangou of Gongnaisi River Basin. The coupled model of soil water and heat is going to be built by analyzing the soil freezing-thaw process. The interpolation method is going to be used for interpolating the soil freezing-thaw process from stations to watershed level. The runoff process and the influence of seasonal soil freezing-thaw process on streamflow are going to be simulated by the modified snowmelt runoff model which combined the coupled model of soil water and heat and hydrological model.

中国西北干旱区内陆河均发源于山区，海拔高，温度低；土壤冻融对山区产流和河川径流的影响是重要的研究课题。本研究试图通过研究季节性冻土区土壤的水热耦合过程来分析季节性土壤的冻融机制，并将土壤水热耦合模块与现有融雪径流模型耦合来分析高寒山区流域季节性土壤冻融过程对径流的影响。将在新疆天山西部巩乃斯河流域的班禅沟建立野外观测实验和控制实验，观测研究季节性土壤冻融过程，地表径流与雨水和积雪融水的关系，构建土壤水热迁移模型，进一步与土壤水热耦合模块与系统动力学模型相结合来构建融雪径流模型，模拟巩乃斯河流域的径流量，分析高寒山区流域季节性土壤冻融过程对径流的影响。

中国西北干旱区内陆河均发源于山区，海拔高，温度低；土壤冻融对山区产流和河川径流的影响是重要的研究课题。本研究通过对季节性冻土冻融过程的观测以及季节性土壤冻融过程对径流的模拟，揭示高寒山区流域季节性土壤冻融过程对径流的影响机制。本研究首先通过通径分析的方法对不同海拔高度季节性冻土冻结深度和解冻日数的影响因素及限制因素进行分析，发现不同海拔高度积极性冻土的影响因素相差不大，但是限制因素差异较大。通过对研究区季节性冻土的时空分布规律进行分析，发现不同海拔高度由于温度和积雪的作用，土壤冻结深度和土壤冻融历时具有显著差异；积雪对冻土的影响表现为积雪覆盖历时越长，土壤冻融历时就越长；积雪最大雪深越深，土壤的最大冻结深度越浅。对森林、积雪和裸地覆盖条件下季节性冻土冻结深度的变化进行监测，发现森林对土壤的隔热作用大于积雪，大于裸地；在森林覆盖下季节性冻土的冻结深度最浅，冻融历时最长。最终通过对基于系统动力学原理构建的SDHydro水文模型在积雪融化速率和不同深度土壤冻融状态两个方面进行改进。该改进的模型可以较好地模拟高寒山区季节冻土广泛分布地区的径流过程，尤其对春季径流过程的模拟效果较好。本研究为高寒山区春季径流过程的变化，以及春季洪水的预防和管理提供理论支撑。