土地精细平整下畦灌二维水流运动特性及畦田布局模式研究

Collective management of rural farmland is a development trend, while corresponding reasonable field layout pattern under precision land leveling is lack of technical support. For this project, based on a large number of two-dimensional basin irrigation experiments, the two-dimensional water flow characteristic of basin irrigation was analyzed, and the two- dimensional basin irrigation model considering infiltration variation was build, in which the numerical simulation model of infiltration spatial distribution was looked as the source item of the complete hydrodynamic model of basin irrigation, and new numerical method was proposed to solve the flow close to the hydrostatic movement caused by infiltration variation. Combining the field experiment with numerical simulation, the influences of the inflow gate type on the irrigation process and performances were analyzed for different basin width and discharge, and the reasonable inflow gate type was proposed. Based on the basin irrigation model and reasonable inflow gate type, the irrigation performances for different water supply condition, soil type and basin size were obtained by simulation. Considering integrative objects for water saving, soil saving and labor saving, comparing optimum design methods, the reasonable field layout patterns for different water supply condition and soil type were proposed, research results can supply technical support for the design of field layout pattern on the condition of collective management of farmland.

农村耕地规模化、集约化经营模式已成为一种发展趋势，而与之相应的精细土地平整下合理畦田布局模式尚缺乏可参依据。本项目拟通过大量田间灌溉试验，在揭示畦灌二维水流运动规律和特性基础上，将开发的入渗空间分布数值模拟模型作为畦灌全水动力学模型的源项，构建起能够精确模拟土壤入渗空间变异及由此引起的水流接近于静水运动过程的畦灌二维水流运动模型；将田间试验与数值模拟相结合，分析不同入畦单宽流量下水流入畦方式对水流运动过程和畦灌性能的影响，提出适宜的水流入畦方式；基于构建的畦灌二维模型和提出的适宜水流入畦方式，获得不同灌溉供水条件、土质和畦田规格下灌水质量指标值，综合考虑节水、节地和省工等目标，分析选取多目标优化设计方法，提出不同供水和土质条件下适宜的畦田布局模式，为农村规模化经营中解决畦田优化布局问题提供技术支撑。

农业生产经营规模化、集约化已成为一种趋势，随着田块规格增大，灌溉水流运动二维特征将更为明显，畦灌入流口位置及分布对灌溉过程及性能影响有必要被进一步了解。为此，本项目开展了不同入流方式下的旱田宽畦灌溉和水稻泡田灌溉试验，开发了考虑微地形和入渗空间变异的畦灌二维水流运动模型；讨论了灌溉二维水流运动特性，分析了入流方式对灌水过程及性能的影响，提出旱田宽畦灌溉适宜的入流方式及水稻田适宜的规格及入流口位置；借助遗传算法，构建了基于多目标的田块优化布局方法。项目取得的主要成果如下：①提出了典型田块上适宜的土壤紧实度采样密度应不低于50个/hm2；②构建了考虑微地形和入渗空间变异的畦灌二维水流运动模型，创新了二维灌溉模型主方程的数学形式及数值解法；③提出了不同供水条件和土地平整状况下冬小麦宽畦灌溉的适宜入流方式：在入畦单宽流量不大于2 L/(sm)的条件下，当田面平整精度Sd≤3cm时，三种入流方式（线形，扇形和角形）间差异不大，如果条件允许可优先考虑线形和角入流，尤其是存在明显局部凸起的情况，可考虑在凸起侧选取角流入口；当3<Sd ≤5cm时，建议采用扇形入流或线形入流；当Sd >5cm时，建议采用线形入流。在入畦单宽流量能到达4 L/(sm)的条件下，建议采用线形或扇形入流。在入畦单宽流量能到达6 L/(sm)的条件下，三种入流方式间差异不大，可根据配水工程施工的方便和局部微地形情况来选用方便可行的任一种入流方式。④提出了不同供水条件下水稻格田灌溉的适宜田块规格和入流方式：当田块入流量小于60 L/s时，水稻泡田灌溉适宜的田块规格是30m×30m，当田块入流量大于60 L/s，适宜的田块规格为50m×50m。若采用两个或三个入流口可适当缩短灌水时间，但考虑到田块规格较小且布设入流口会增加建设成本，建议选择一个入流口布设在畦宽中间位置。