荒漠绿洲非饱和带土壤水分运移及对地下水补给作用

The vadose zone is the zone in between the land surface and above the water table at vertical profile with partial water saturation, where constitutes the connections between atmospheric water, surface water and groundwater. Limited knowledge of the moisture migration behaviors in the vadose zone has been a bottleneck in determining the rates of groundwater consumption and recharges in arid regions. As such, the proposed project will substantially contribute to solving those issues that desert oasis system is now confronted, through both intense monitoring efforts and enhanced investigation at Linze Inland River Basin Research Station, CERN. There are five major concerns included in this project: 1) soil hydrologic and physical properties, and vertical transfer of soil moisture in the representative soil profiles along a selected transect; 2) influences of soil structures on moisture transfer in the vadose zone of both rainfed and irrigated landscapes; 3) hydraulic connectivities and water transfer on the interfaces between the irrigation farmland, sand dunes, wetlands, lakes, and other landscape types; 4) soil moisture recharges in the vadose zone through groundwater abstraction, and the factors controlling the processes; 5) moisture migration behavior in the vadose zone and the potential effects on groundwater dynamics. Through our investigation, the minimum irrigation requirements and optimal irrigation strategy will be determined for farmlands of different ages to maintain a certain level of water transfer or keep reasonable hydraulic connectivities between the farmlands and their neighboring landscape elements. The recharge rates of precipitation and lateral flow of river water to groundwater system, and the water storage in vadose zone will also be estimated at the rainfed deserts or sand-dune dominated landscapes for characteristic hydrological years.

包气带指地表与地下水之间垂直剖面中土壤孔隙没有被水充满的区域，是地表水与地下水通过土体转换的通道，对包气带水分运移规律缺乏深入系统了解已成为确定干旱区地下水消耗、补给速率的瓶颈。本项目以中国生态系统研究网络临泽站为依托，针对荒漠绿洲包气带土壤水分运移及其对地下水补给等科学问题，开展荒漠绿洲样带典型剖面包气带土壤水文物理性质与土壤水分垂直运移；雨养和灌溉条件下土壤结构对包气带水分运移的影响；灌溉农田、沙丘、湿地、湖泊景观相邻界面水分交换过程及水力联系；地下水对包气带水分补给过程及影响因素；包气带水分运移及其对地下水变化影响评估等研究，旨在量化不同开垦时间绿洲维持灌溉水补给到地下水最小灌溉量与灌溉模式，确定绿洲灌溉农田与相邻景观界面保持水分交换最小灌溉量，阐明雨养条件下典型降水事件和年尺度上砾质荒漠和沙丘样地扩散补给、局地补给和存储于土壤中水分的比例及主要影响因素，提升干旱区土壤水文学研究水平.

根据计划书，本项目研究内容包括：1）荒漠绿洲样带典型剖面包气带土壤水文物理性质与土壤水分垂直运移；2）雨养和灌溉条件下土壤结构对包气带水分运移的影响；3）灌溉农田、相邻沙丘、湿地和湖泊景观界面水分交换过程及水文连通；4）地下水对包气带水分补给过程及影响因素；5）包气带水分运移及其对地下水变化影响评估等。 .项目构建了荒漠绿洲4种景观带典型剖面包气带水分运移机制模型，定量刻画了低含水量条件下薄膜水、毛管水运移过程；2) 揭示了绿洲发育对地下水补给特征的影响规律，量化了不同土壤条件下补给地下水的灌溉阈值；3) 初步建立了灌溉与地下水波动的关系，评估了灌溉对绿洲景观间水力联系的影响。4）评价了河西走廊绿洲地下水可持续性状况及其影响因素。项目迄今共发表论文34篇，其中在《Water Resources Research》《Soil & Tillage Research》《Journal of Hydrology》《Hydrology and Earth System Sciences》《Agricultural and Forest Meteorology》《Land Degradation & Development》等领域内Top期刊发表论文14篇。项目执行中申报了两项发明专利（实质审查阶段）。项目成员参加学术会议20余次，做学术报告10人次；项目2名骨干成员晋升为研究员，2名晋升为副研究员，1人入选中科院青促会会员，1人入选中组部、中科院“西部之光”人才计划；培养研究生10名，1名博士研究生获得国家奖学金，形成了一个绿洲土壤水文学研究团队。 .部分研究成果为中国科学院2020-2021年院士咨询项目“干旱区生态建设与农业可持续发展对策”报告的撰写提供部分依据。基于本项目成果撰写的《优化农业空间布局推动绿洲农业提质增效》和《发掘绿洲边缘区节水潜力补充绿洲农业用水》决策报告分别被甘肃省科技厅和农业农村厅采用，为干旱区水资源合理开发利用和生态环境建设提供了科学依据。有关荒漠绿洲包气带水分运移成果大部分是2020年以后发表的，但已被国内外同行引用200次，其中在水文、土壤等领域Top期刊《Water Resources Research》《HESS》《JH》《AFM》《STR》它引160余次，得到了国内外同行认可，提升了干旱区土壤水文学研究水平。