As it mixes with colder air, there are very violent up currents and down currents and swirling eddies of air, and great clouds foam.

当它与较冷的空气混合时，会有非常猛烈的上升气流和下降气流，空气漩涡和巨大的云层泡沫。

They have also built stone weirs across these canals at regular intervals, to slow the current down still further and encourage water to spill over the canal banks.

他们还在渠道上一定的位置建上了石堰堤，这样做一方面可以降低水的流速，另一方面还可以使水流溢出堰堤。