基于SWAT-MODFLOW耦合模型的区域尺度作物水足迹量化方法研究

Agricultural is the largest department of water resources consumption in China. Scientific evaluation and management of agricultural water use is the prerequisite for the efficient utilization of water resources. The water footprint provides the indicators for this evaluation and management process, Accurate and comprehensive quantification of crop water footprint is of great significance for the evaluation and management of regional agricultural water use. Currently, the circulation and transformation mechanisms between shallow surface water and groundwater remain unknown, and the method of accurately quantifying crop water footprint which reflects the utilization of surface water and groundwater by crops hasn’t been established. In this project, we will take Hetao irrigation area in Inner Mongolia as the study object, simulate the circulation and transformation processes among each hydrological element through the SWAT-MODFLOW coupled model, and explore the transformation mechanism between regional surface water and groundwater during crop growth. Furthermore, combined with the water footprint theory, the sources and characteristics of crops' blue and green water consumption during the hydrological cycle in irrigated areas will be analyzed and clarified, and the method of quantifying region-scale crop water footprint based on the hydrological process will be established. According to the different future climate scenarios provided by IPCC, the variation characteristics and influencing factors of crop water footprint in different scenarios will also be analyzed; and the response mechanism of crop water footprint to climate change will be revealed. Those studies would provide hydrological process mechanism for quantifying regional crop water footprint and offer theoretical foundation for coping with the impact of climate change on crop water footprint.

农业生产是我国水资源消耗的最大部门，科学合理地评价管理农业用水是实现水资源高效利用的前提。水足迹为该评价管理过程提供了指标，准确全面地量化作物水足迹对区域农业用水的评价、管理具有重要意义。针对目前地下水埋深较浅区地表水、地下水循环转化机制不明，缺乏科学反映作物对地表水和地下水利用的作物水足迹量化方法的现状，项目以内蒙古河套灌区为对象，通过建立灌区SWAT-MODFLOW耦合模型，模拟灌区农业生产中各水文要素的循环转化过程，明确作物生长过程中区域地表水地下水的转化机制；结合水足迹理论，厘清并分析灌区水文循环过程中作物蓝、绿水的消耗来源及特征，建立基于水文过程的区域尺度作物水足迹量化方法；根据IPCC不同气候模式数据，分析作物水足迹在不同情景下的变化特征及影响因素，揭示作物水足迹对气候变化的响应机制，以期为区域作物水足迹的量化提供水文过程机理，并为应对气候变化对作物水足迹的影响提供理论支撑。

科学合理地评价农业耗用水情况是实现水资源高效利用的前提。水足迹作为评价管理用水的重要指标，全面准确地量化水足迹对区域农业用水的评价、管理具有重要意义。针对目前地下水埋深较浅区地表水、地下水循环转化机制不明，缺乏科学反映作物对地表水和地下水利用的作物水足迹量化方法的现状，项目以内蒙古河套灌区为对象，通过建立灌区SWAT-MODFLOW耦合模型，模拟灌区农业生产中各水文要素的循环转化过程，分析灌区水文循环过程，解析其中与农业生产相关的水文要素，构建了基于水文过程的区域尺度作物生产水足迹量化方法，基于此方法模拟评估未来气候变化对作物生产水足迹的影响。获得的主要结果包括：河套灌区水循环以垂向运动为主，灌区水资源主要来源是灌溉水和降水，灌溉水占水资源总量的71%以上；灌区水资源主要消耗项是蒸散发（占消耗总量的77%以上），其中主要是农作物蒸散发，灌区自然植被生长依赖于灌区的浅层地下水，灌溉对维持灌区地下水位有重要作用；通过分析灌区农业生产中水循环过程和水足迹构成要素，提出了基于水文过程的区域尺度作物生产水足迹量化方法，较以往量化方法在空间上增加作物对灌区渠系渗漏水的利用和对地下水的利用，在时间上包含了服务于作物生长的种植前后时期的水分消耗，更全面反映作物生长的水分利用效率，在河套灌区，三种作物生产水足迹中，蓝水足迹占85%以上；气候变化会影响作物生产水足迹的构成及大小，降水会改变作物绿水消耗进而影响蓝水消耗量，气温则通过蒸散发影响作物生育期内蓝绿水的消耗，进而改变作物生产水足迹。研究成果有助于灌区农业用水情况的评估，对提升灌区农业用水效率具有重要意义。