干旱扬水灌区(景电灌区)水盐运移对区域水土环境的影响研究

Influenced by large external water resources and artificial irrigation, water-salt transport in arid pumping irrigation area has its own special characteristic and its impact on the regional water-soil environment is long and slow, which is hard to master in a short period. Choosing a typical case study area, performing continuous monitoring and experiment simulation, discovering microcosmic water-salt transport law and its influence on process and law of macroscopic water-soil resources change, will be of great importance in researches related to regional water-soil environment revolution law and driving mechanism..The project area is Jingdian irrigation area, located in the south margin of Tengger Desert, which is extremely arid and its water-soil environment is relatively close. Macroscopically, remote sensing technique is used for the large scale monitoring. Microcosmically, analysis of long term samples monitoring data, numeric simulation and typical area experiment will be used to simulate water-soil transport law and its impact on regional macroscopic water-salt revolution and distribution pattern. The cloud theory based coupling model will be developed to analyze the coupling relationship between regional water-salt transport and water-soil environment change, discover the processes and driving mechanism of how regional dynamics water-salt influencing water-soil environment from both the time and space series, and predict middle and long term water-soil environment revolution tendency. The research presented here will provide theoretic proof for the water-soil environment revolution in north-west arid pumping irrigation area and innovative research in the coupling relationship between water-soil environment revolution and complicated media and multi-process.

受大量的外调水资源和人工灌溉的影响，干旱扬水灌区内的水盐运移具有独特性，其对区域水土环境的影响是长期潜在而缓慢的，短期内不能完全掌握。通过选定典型的研究区域，开展连续的监测和试验模拟，揭示微观的水盐运移规律和对宏观水土资源变迁的影响程度和发生过程，对区域水土环境演变规律和驱动机理领域的研究具有重要意义。.本项目以地处腾格里沙漠南缘、气候极度干旱且水土环境相对封闭的景电灌区为研究区域，宏观上应用遥感进行大尺度监测，微观上通过长序列的定位监测资料分析、数值模拟和典型区试验,模拟灌区土壤水盐运移的规律，评价其对区域宏观水盐演化和分布态势的影响；建立基于云理论的耦合模型，明晰灌区水盐运移与区域水土环境变迁的耦合关系，揭示区域水盐动态对水土环境在时间和空间序列上影响的显现过程和驱动机理，预测区域中长期的水土环境变迁趋势，为我国干旱扬水灌区水土环境演化与复杂介质多过程耦合的创新研究提供理论依据。

甘肃省景电灌区是地处干旱荒漠区的一个生态系统完全开放而水土资源环境相对封闭的大型扬水灌区，灌区建成于上世纪70年代初，经过40多年的运行，灌区的地下水盐运移态势、土地利用类型、水土资源空间分布等环境因子的响应变迁已逐步显现。本项目通过长序列的实地监测、遥感影像解译、典型区的数值模拟、多层次模糊评估和云模型转换求解等综合方法，对干旱扬水灌区水盐运移对区域水土环境变迁影响进行了研究。研究成果如下： 1）运用HYDRUS-2D/3D模型分别对干旱灌区轮灌及沟灌模式下土壤微观的水盐运移进行模拟，模拟发现：灌水淋洗可显著降低田间土壤含盐量，在灌水间隔期及次数己定的条件下，灌水定额越大，土壤脱盐深度越大，上层整体脱盐率越高，其中沟灌模式下脱盐率大小依次是：常规沟灌>交替隔沟灌>固定隔沟灌。2）灌区内地下水盐的演化运移主要受控于灌溉水入渗。灌区内开敞型水文地质单元水盐运移呈地下潜水径流通畅、溶质迁移滞缓的特点，封闭型水文地质单元水盐运移具有径流滞缓、水盐积累的特点。3）针对干旱扬水灌区水土环境变迁响应评估问题，分别采用了改进层次分析法和云模型转化的评价方法。结果表明两种评价方法得出的结论相一致，评价结果表明：灌区提水量、灌溉引水量、地表水水质是造成水土环境变迁的敏感因素，其次是地下水和区域气候，土地利用最为迟缓。4）灌区的灌溉和水盐运移对区域景观格局影响较大。在灌区引水灌溉之后，随着人工绿洲的建设和发展，使得原来的沙漠绿洲景观逐步变迁为荒漠绿洲的景观格局，灌区内农林板块和面积比例均增加很多，相对地固定沙地、半固定沙地和移动沙地的板块和面积比例均下降较大。5）采用数值分析软件MATLAB径向基神经网络（RBF）方法，根据已知年地下水水位的变化趋势对景电一期八个测站地下水水位在未来5年的变化态势进行了预测，研究结果表明：八个测站已知年地下水水位变化各异，且未来5年变化态势与已知年地下水变化过程基本上相似，均在未来5年呈上升趋势。