They built up an earthen dam in time. 他們及時(shí)地建起了土壩。
The studies may indicate that an earthfill dam with a center concrete gravity overflow spillway section is the most economical, in a wide flat valley. 方案表明，在寬闊而平坦的河谷內，一種在中間段設置混凝土重試溢洪道的土壩是最經(jīng)濟的。
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