节水改造对盐渍化灌区水土环境的影响及节水调控机制研究

The large-scale water-saving improvement works and transition projects of water right in Hetao Irrigation District in Inner Mongolia cause the decrease of diverted and drainage water capacity in Yellow River and sinking regional groundwater table that threatening local soil and water environment and leading to inefficient farming mode. The project mainly discusses the releated issues on changing soil and water environment by long-term, large-scale water-saving transformation. The evolution mechanism of HeTao irrigation district's soil and water environment which has undergone water-saving improvement works will be analyzed and the effect of water saving on regional soil salinity and groundwater level will be figured out by using data collection, location sampling, lysimeter, remote sensing inversion and other means. At the same time, exploring the responding to different groundwater level for crops and salt and water movement of saline soil and assuring the quantitative relationship between crop - diving evaporation - soil salinity - groundwater level under different groundwater conditions and a reasonable ecological groundwater level after water saving will be proposed. In addition, this research takes irrigation area as study scale and the MODFLOW-SWAT coupling model will be established which for shallow groundwater area and making the reasonable diverted water volume from Yellow River ,the flow of sewage and their operating time of irrigation area in HeTao. Finally, the water saving regulation mode in irrigation scale will be proposed which could lay the foundation and provide theoretical basis for the large-scale water-saving transformation of salinized irrigation area and other similar areas.

随着内蒙古河套灌区大规模节水改造与水权转让项目的实施，引排水量骤减，导致区域地下水位下降，农田水土环境发生显著变化。本项目针对长期、大规模节水改造导致的水土环境演变及相关问题开展研究。采用资料收集、定位取样、蒸渗仪小区试验、遥感反演、模拟研究等手段，分析节水改造后河套灌区水土环境的演化机制，明确节水改造对区域土壤盐渍化和地下水位的影响效应；同时探索不同地下水位对作物及土壤水盐过程的影响，确定不同地下水位条件下作物-潜水蒸发-土壤盐分-地下水位定量关系，并提出节水改造后合理的生态地下水位；以灌域为研究尺度，针对浅地下水地区构建MODFLOW-SWAT耦合模型并进行模拟分析，从而确定灌域合理的引排水量及引排时段，最终提出节水改造后灌域尺度的节水调控模式，为节水改造后盐渍化灌区水分高效利用及其它类似区域开展大规模节水改造奠定基础和理论依据。

本项目针对节水改造后河套灌区水土环境变化问题，分析河套灌区节水改造前后导致地下水环境、土壤盐分的动态变化，基于遥感技术对节水改造前后典型年份的土壤盐碱度、盐荒地面积进行定量研究。针对地下水位下降引起的水土环境变化等问题，基于地中渗透仪，以玉米作为研究对象，通过设置不同地下水埋深对玉米株高、叶面积指数进行对比分析，探究玉米生长对不同地下水埋深处理的响应机制，发现不同地下水埋深下玉米根系吸水能力的差异导致了玉米各项生理指标的差异。定量研究了包气带中水分转换关系和变化规律，探讨各个水分均衡项对不同地下水埋深的响应。分析了玉米各个生育期内包气带/根系层土壤含水率对不同地下水埋深的响应，探究了不同时间尺度下地下水补给量对灌溉与地下水埋深的响应。随着内蒙古河套灌区大规模节水改造的实施，引排水量骤减，导致区域地下水位下降，农田水土环境发生显著变化。本研究针对长期、大规模节水改造导致的水土环境演变及相关问题开展研究。基于水盐均衡理论，确定不同水文年份下灌区合理引排水量比；通过构建灌区分布式水文水质SWAT模型，确定河套灌区径流与氮素流失机制。