地下水浅埋干旱灌区农业节水的水文生态效应及优化调控研究

Quantitative evaluation of the effects of agricultural water-saving on agro- and eco-hydrology, as well as the management optimization, is very important and significant for developing the appropriate agricultural water-saving practices (WSPs) in arid irrigation districts. In this study, the Hetao Irrigtion District in Inner Mongolia is selected as typical study area with arid shallow water table conditions, while the Nanxiaozhao Irrigation System (NIS) was chosen as the typical case study area. The grid-based field observation experiment related to the agro- and eco-hydrologic processes is to be carried out in NIS. While, the satellite remote sensing data is applied for monitoring the regional soil salinity and vegetation growth. These two are used to explore the dynamics of subsurface water, salinity and vegetation growth and their impact factors. Then a quasi three-dimensional variably saturated water-salt transport and crop-growth simulation model (VSMOD) is to be developed for arid irrigation districts with considering the conditions of soil freezing and melting, different landscape units and shallow water tables. The VSMOD model is based on the coupling of a vertically one-dimensional agro-hydrological model and a three-dimensional groundwater flow and solute transport model. Then the VSMOD model of NIS is to be constructed with strict calibration and validation. After that, it will be used to clarify the spatial and temporal dynamics of water and salt in and among landscape units, and to quantitatively evaluate the effects of different WSPs on agro- and eco-hydrology. Further, a multilayer regional optimization model for water and land planning is to be developed based on the combined use of process model and optimization model. Finally, we will attempt to search the appropriate integrated water-saving mode through the combination of VSMOD and the proposed regional optimization model. In summary, this research could extend the quantitative methods on simulation of agro- and eco-hydrological processes and management optimization in irrigation districts. Meanwhile, it can also provide an efficient tool as well as a reference case for developing the suitable agricultural water management strategies for arid irrigation districts with shallow water tables.

合理定量评估农业节水的水文生态效应及综合措施的优化决策，对于干旱灌区建立适宜的农业节水模式具有重要意义。本研究拟以典型地下水浅埋干旱灌区—内蒙河套灌区为研究区，选取典型区（南小召试验区）开展农业-水文生态的网络定位观测试验与区域遥感监测，分析不同景观单元水盐与植被生长动态及影响因素；发展考虑不同景观、土壤冻融、浅埋条件的准三维饱和-非饱和带水盐运移及植被生长多过程耦合模型VSMOD；建立典型区VSMOD模型，模拟剖析灌区水盐在不同景观单元内及单元间的迁移转化规律，定量评估不同农业节水情景下的农业-水文生态效应；进一步构建结合过程模型的灌区多层经济效益优化模型，并结合VSMOD模型提出以节水控盐、粮食稳产和生态健康为目标的适宜农业节水模式及节水潜力。研究成果将是对灌区生态水文过程模拟及管理决策方法的重要补充，同时也可为地下水浅埋干旱灌区制定适宜的农业综合节水模式提供有效工具与案例参考。

合理定量评估农业节水的水文生态效应及综合措施的优化决策，对于干旱灌区建立适宜的农业节水模式具有重要意义。本研究以地下水浅埋干旱灌区为研究对象，围绕灌区多尺度农业水文-生态过程定量化方法与调控管理中存在的现实问题，选取内蒙古河套灌区—机缘研究区为典型区，开展了基于野外综合观测试验、遥感监测和多过程模型相结合的灌区多尺度农业水文-生态过程模拟与优化调控研究。主要的研究内容和取得的成果如下：（1）构建了能灵活处理地表复杂条件、稀疏植被/天然植被和盐渍化影响的农田水文-生态模型，结合观测试验数据在农渠尺度（羊场渠）与灌区尺度（机缘研究区）进行了模拟应用，定量解析了地下水浅埋灌区农田及天然地水盐动态与累积规律、耗用水转化机制和灌溉水利用效率提升途径；（2）提出了有机结合多尺度田间采样、GIS/RS技术和溶质运移模型的集成盐渍化研究体系方法，于河套灌区开展了典型区、农渠（农业生态系统基本单元）、田块（农田及天然荒地）三级尺度的盐渍化时空特征分析，获得了不同尺度的盐分累积分布规律及其主控因子，量化明晰了天然地的干排水机制；（3）发展了集成土壤水盐运移、渠沟地表水、地下水分区平衡和植被生长于一体的灌区尺度分布式农业水文-生态多过程耦合模型，结合机缘研究区综合观测试验与遥感数据对模型进行了系统的测试与检验，提升了传统模型在地下水浅埋干旱灌区应用中存在的多过程考虑不充分及难于进行情景分析的不足之处，进一步定量评估了不同农业节水情景下典型区农业-水文生态效应，提出了以节水控盐、粮食稳产和生态健康为目标的灌区适宜农业节水措施。研究成果将是对灌区生态水文过程模拟及管理决策方法的重要补充，同时也可为地下水浅埋干旱灌区制定适宜的农业综合节水模式提供有效工具与案例参考。