陆地水循环过程的综合集成与模拟

The terrestrial water cycle is influenced by a wide range of climatic variables and human disturbances. In the era of the Anthropocene, when humans drive the changes in atmospheric and hydrological processes in river basins, there is an urgent need for scientists to include human impacts in the study of the natural terrestrial water cycle. The investigation of the natural and human-induced changes in the terrestrial water cycle and the development of comprehensive terrestrial hydrological models are important topics in hydrology, water resources, climate change, and sustainability and development research..The objectives of the study are three folds: 1) to develop an integrated water systems model, which is able to build dynamic connections between hydrology and other components of the earth system and represent anthropogenic manipulations in the terrestrial water cycle; 2) to understand the uncertainty associated with the newly added modules of the model and to evaluate the performance of the model at the regional scale; 3) to quantitatively assess the impacts of anthropogenic manipulation, climate change and land use/cover change on regional water cycle, and project future changes in hydrology and water resources in China. This study will incorporate a crop model and a human intervention module in the Distributed Biosphere Hydrological (DBH) model, which is one of the global hydrological models used in the climate change impact assessments for the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). In addition, the dynamic interactions between ecological water use, human water needs and reservoir operation will be simulated in the improved DBH model. This model will then be used to assess the vegetation (crop) responses to warming and CO2 concentration increase and their effects on ecological water use and irrigation water demands..The downscaled global climate model (GCM) outputs of the latest climate change scenarios (representative concentration pathways; RCPs) and Shared Socio-economic Pathways (SSPs) will be used to force the improved DBH model and to project future water availability in the Yellow River Basin. The study will highlight the responses of terrestrial water cycle to human intervention and vegetation (crop) changes in a changing environment.

水循环是联系陆地表层系统的关键纽带，在人类用水活动和气候变化影响下，陆地水循环过程发生了显著变化，并引起了一系列相关资源环境问题。深入认识陆地水循环过程的变化机理，发展陆地水循环过程的综合集成模型，模拟和预估变化环境下陆地水循环的变化及其水资源效应，是当前水循环研究面临的紧迫任务。本项目拟在IPCC AR5影响评估模型DBH的基础上集成作物模型、工程调节和社会需水模块，以完善人类用水活动过程的参数化；以黄河流域为试点区域，根据水文水资源观测和统计资料，分析新增模块的不确定性及其对模型整体性能的影响，评估改进模型的区域适用性；使用改进模型阐明人类用水活动和气候变化影响区域水循环过程的关键机制，预估社会经济发展和气候变化情景下水循环的变化过程及水资源短缺风险。本研究为厘清变化环境下陆地水循环变化过程及其效应提供理论和实践基础，可为区域水资源配置以及应对全球变化战略决策提供科学支持。

陆地水循环是联系地球表层系统的关键纽带，决定水资源时空分布及其支撑下的生态环境演变。气候变化和人类活动多重因素的影响增加了陆地水循环变化模拟和归因的困难。本项目按照研究计划开展了人类用水过程参数化/模块改进及综合集成模拟模型构建、不同尺度的水循环演变及归因分析以及未来水文情势变化及其主要驱动因素识别等方面的研究。具体包括以下几个方面：（1）发展了流域水库闸坝多目标调控参数化方案，改进了作物模型的辐射模拟方法和灌溉下渗过程模拟，完善了陆面水文模型中的地下水模拟模块，评估了社会需水模拟模块并重建了人类用水数据。改进了陆地水循环综合集成模拟模型DBH，其中耦合了水库调控、水动力学和水能相互作用模拟等模块，对模型进行了验证和应用研究，评估了模型性能和适用性。（2）基于综合集成模型，分析了水循环历史变化趋势及其驱动因素和机制，定量区分了人类活动和气候变化对水循环变化的贡献。结果显示，黄河源区径流变化主要受气候因素影响，中下游部分人类用水强度较大地区，人类活动对径流的影响占主导作用（贡献率为57%至91%）。（3）基于第五次耦合模式比较计划（CMIP5）多个全球气候模型的气候预估数据和未来土地利用变化预估结果，利用综合集成模型预估了不同情景下未来陆地水循环变化，评估了未来极端天气和水旱灾害变化情况。研究结果显示，径流对未来全球平均气温上升幅度的响应是非线性的，其中升温1.5°C左右是一个关键转折点。未来灌溉作物面积扩张是水资源消耗的主要驱动因素，本世纪末作物的蓝水消耗将增加70%左右。在黄河流域上游，未来气候变化仍然是径流变化的主要驱动因素。该项目研究成果为陆地水循环变化模拟及其归因、水旱灾害监测和预报等提供了有效的科学工具。