黄河河源区径流对土地覆被和气候变化的响应

该文选择黄河河源区作为典型流域，把握这一特殊大尺度流域的自然地理特征，在分析流域气候、水文和土地覆被变化特征后，应用分布式水文模型进行径流模拟，得到了不同气候和土地覆被变化的水文效应.针对模拟结果，设计并计算不同气候和土地覆被情景下的黄河河源区径流变化趋势.该文在黄河流域水循环地理信息系统支持下，对黄河河源区80~90年代土地覆被状况和近50年来水循环要素(气温、降水和径流)展开了分析探讨，得到以下结论:●通过对黄河河源区土地覆被结构与变化过程、空间景观特征和不同类型土地覆被重心转移的研究表明，流域土地覆被类型的多样性和异质性增加，土地覆被正朝多样化和均匀化的方向发展;流域高覆盖度草地正在向中低覆盖度草地转变，唯一保留的高覆盖度草地分布在黄河河源区的东南缘.●近50年来，代表黄河河源区西北部降水稀少的玛多站年降水量呈现出小幅度上升趋势.流域东南部降水量较多的久治站则呈现出下降的趋势，尤其是90年代下降得最快.●多年平均流量基本保持不变，不同年代之间有所变化，80年代径流量最大，90年代急剧下降.该文最后建立了5种土地覆被情景模型以及24组不同气温和降水的情景组合.利用SWAT模型分别模拟不同情景下的年均径流量和径流深.该文主要研究进展为:●理论上总结了地理信息系统与水文学研究四种结合方式，提出地理信息系统支持下流域水循环研究的一般模式，从数据统一编码的角度对水循环要素数据进行统一管理.●建立了黄河流域水循环地理信息系统平台，并在该平台基础上对黄河流域土地覆被进行综合分类，该成果为研究黄河流域水循环要素的演变规律提供支撑平台.●提出了气候与土地覆被变化下的流域径流研究的一般框架.基于物理基础的分布式水文模型SWAT被应用于资料缺乏的空间大尺度的黄河河源区，结合遥感资料，在地理信息系统的支持下，得到了较好的模拟结果.定量计算结果认为黄河源区土地覆被和气候变化是影响黄河河源区径流变化的主要因素，尤其是降水量的多少对流域径流量的影响最大.●在SWAT模型中，通过参数调整，总结归纳出SCS降雨-径流模型中CN值在黄河河源区的适用范围，为该模型在黄河河源区应用提供理论支撑。This paper selects the source region of the Yellow River as a typical basin, focusing on the physical geographic characteristics of this special large-scale basin. After analyzing the climate, hydrology and land cover change characteristics of the basin, it applies the distributed hydrological model to conduct runoff simulation, and obtains the hydrological effects driven by different climate and land cover changes. Based on the simulation results, it designs and calculates the runoff change trends of the source region of the Yellow River under various climate and land cover scenarios. Supported by the Geographic Information System (GIS) for water cycle of the Yellow River Basin, this paper analyzes and discusses the land cover status of the source region of the Yellow River in the 1980s and 1990s, as well as water cycle elements (air temperature, precipitation and runoff) over the past 50 years, and draws the following conclusions: ● Research on the land cover structure and change process, spatial landscape characteristics and gravity center transfer of different land cover types in the source region of the Yellow River shows that the diversity and heterogeneity of land cover types in the basin have increased, and land cover is developing towards diversification and homogenization; the high-coverage grassland in the basin is transforming into medium and low-coverage grassland, and the only remaining high-coverage grassland is distributed in the southeastern margin of the source region of the Yellow River. ● Over the past 50 years, the annual precipitation at Maduo Station, which represents the arid northwest of the source region of the Yellow River, shows a slight upward trend. While Jiuzhi Station, located in the wetter southeast of the basin, shows a downward trend, with the most rapid decline occurring in the 1990s. ● The multi-year average runoff remains basically unchanged, with fluctuations across different decades: the runoff peaked in the 1980s and dropped sharply in the 1990s. Finally, this paper establishes 5 land cover scenario models and 24 sets of scenario combinations of different air temperature and precipitation. The SWAT model is used to simulate the annual average runoff and runoff depth under each scenario respectively. The main research progresses of this paper are as follows: ● Theoretically summarizes four combination modes of Geographic Information System and hydrology research, proposes a general framework for basin water cycle research supported by GIS, and uniformly manages water cycle element data from the perspective of unified data coding. ● Constructs the GIS platform for water cycle of the Yellow River Basin, and conducts comprehensive classification of land cover in the Yellow River Basin based on this platform. This achievement provides a supporting platform for studying the evolution laws of water cycle elements in the Yellow River Basin. ● Proposes a general framework for basin runoff research under climate and land cover changes. The physically based distributed hydrological model SWAT is applied to the data-scarce large-scale spatial source region of the Yellow River, and good simulation results are obtained with the support of GIS combined with remote sensing data. Quantitative calculation results indicate that land cover and climate change in the source region of the Yellow River are the main factors affecting runoff changes in the source region, especially the amount of precipitation has the greatest impact on basin runoff. ● In the SWAT model, through parameter adjustment, the applicable range of CN value in the SCS rainfall-runoff model for the source region of the Yellow River is summarized, providing theoretical support for the application of this model in the source region of the Yellow River.