“三通”结构形式的不同会造成不同的局部水头损失，对灌溉运行费用影响很大，所以对三通结构进行优化，减小灌溉水头和局部水头损失有相当大的意义。

The different structure of the three-way pipe lead to the different local loss of head, it cause a great influence on operating costs of irrigation.

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负压灌溉法是一种新近提出的节水灌溉技术，灌溉时供水水头为“负值”，即灌溉水源高程低于灌水器高程。

Negatively pressurized irrigation (NPI) method, a newly irrigation technology, in which the elevation of the emitters is higher than that of the water source, runs under negative hydraulic head.

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以压力水头为因变量的数学模型可以模拟供水压力和灌水器特性对灌溉效果的影响。

A mathematical model whose variable is water head can simulate the effects of water head and properties of subsurface irrigation pipe on irrigation.

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