内陆河高山冻土带降雨-径流产汇流过程研究

The upper reaches of the inland rivers are the main regions that precipitation falls and runoff generates in the basins, as well as a lot of permafrost exist. The existence of permafrost increases the complexity of the rainfall-runoff processes and the uncertainties of runoff processes of the inland river basins. Studying the rainfall-runoff processes and water flow routing in permafrost region will help us to deepen the understanding of Hydrology in inland rivers, and is of great significance for scientific management and rational utilization of water resources in inland rivers. This research intends to select the upper reaches of the Shule River, where permafrost covered over 80% of the whole region, as the typical study area. Based on the observations of rainfall-runoff process and isotope tracer in some small watersheds, the relation of water table change and thaw-froze process of permafrost active layer, and the runoff separation in permafrost regions, rainfall-runoff processes and runoff compositions will be determined. Using the data of precipitation, temperature, vegetation, and results of isotopic runoff separation, the impacts of different factors on permafrost runoff formation and changing process will be studied. Based on the analysis above, the VIC model (Variable Infiltration Capacity) and the dynamic three-dimensional groundwater model (MODFLOW-USG) will be used to quantify the spatial and temporal rainfall-runoff processes, and the groundwater-runoff interactions in different freezing-thawing processes. And the coupled change scenarios of permafrost, climate, and vegetation will be set to analyze the sensitivity of watershed runoff and base flow, in order to clearly understand the rainfall-runoff change mechanism in permafrost region of inland river basins.

内陆河上游山区是流域主要的降水带及产流区，同时也是典型的冻土分布区。多年冻土的存在使得内陆河上游产汇流过程更加复杂，增加了流域水文变化的不确定性。研究清楚内陆河高山冻土带的降雨-径流过程及水流转化机制，对于掌握内陆河径流形成和变化规律、合理利用水资源有重要意义。为此，本项目选择多年冻土覆盖率近80%的疏勒河上游为典型区，拟通过天然小流域“降雨-径流”过程观测、冻土活动层雨水分配示踪、“降雨-活动层冻融过程-地下水位”关系分析、同位素径流分割等，确定内陆河高山冻土带的“降雨-径流”产汇流过程及冻土区径流构成；在此基础上，应用VIC模型和三维地下水模型MODFLOW-USG模拟冻土区“降雨-径流”过程及时空变化，量化不同冻融阶段地下水与河道径流的动态转化关系；耦合气候-植被-冻土动态变化情景，对流域产水及过程变化进行敏感性分析，确定内陆河高山冻土带的“降雨-径流”产汇流影响机制。

内陆河水资源是中国西北干旱区生产、生活及生态需水的重要保障。中国西北约43.5%的面积为山地，而内陆河大都发源于此。地表水-地下水动态转化关系是内陆河上游水文过程研究的核心问题。而西北内陆河高山冻土带往往与山区主要降水带重合，是内陆河最主要的产水区。疏勒河是西北第三大内陆河，其上游山区80%以上面积为冻土覆盖。冻土的存在，加大了降雨产汇流过程的复杂程度。加上高寒环境、观测难度加大，使得目前针对这一主要产水带的降雨-土壤水-活动层地下水-河道径流迁移转化问题研究比较缺乏。本项目的研究有助于提高内陆河流域水文的认识水平。. 研究清楚内陆河高山冻土带的降水-径流过程及水流迁移转化规律，对于掌握内陆河径流形成变化规律和合理开发利用水资源有重要意义。本项目选择多年冻土覆盖率近80%的疏勒河上游为典型区，通过天然小流域“降雨-径流”过程观测、冻土活动层降雨分配示踪、“降雨-活动层冻融过程-地下水位”关系分析、同位素分割径流等，确定内陆河高山冻土带的“降雨-径流”产汇流过程及冻土区径流构成；在此基础上，应用VIC模型（Variable Infiltration Capacity）量化了冻土区“降雨-径流”过程时空差异，以及不同冻融阶段河道径流与地下水动态转化关系；通过耦合气候-植被-冻土动态变化情景，对流域总径流及基流变化进行敏感性分析，分析确定内陆河高山冻土带的“降雨-径流”产汇流影响机制。. 本研究通过大量的观测和实验分析，基本掌握了高寒冻土带活动层冻融过程对地表水-活动层地下水转化关系及降雨产汇流过程的影响。获取的观测数据、参数以及研究结论有助于加深高寒区水文学的认识，可为西北干旱区的水资源研究及开发利用提供参考。高寒环境的第一手观测数据非常珍贵，对于缺乏观测区有很好的数据补充作用，可有效促进这一特殊地区冻土水文定性认识向定量研究的发展。