１９９９年１０月２５日上午１０时，随着三颗红色信号弹在黄河中游峡谷升空，重达１００多ｔ的小浪底工程３号导流洞巨型闸门缓缓降落。约１０分钟后，奔腾的黄河再度被拦腰截断，小浪底水利枢纽正式下闸蓄水。这是该工程继１９９７年１０月实现大河截流后的又一重大阶段性成 At 10 a.m. on October 25, 1999, with the passage of three red signal flares over the canyon in the middle reaches of the Yellow River, the giant sluices of the diversion tunnel No. 3 of the Xiaolangdi Project weighing over 100 tons dropped slowly. About 10 minutes later, Pentium Yellow River cut off again by the middle, Xiaolangdi Hydro Project officially under the gate. This is another major phase of the project following the closure of the river in October 1997