当水到达合适的水位时，幼鸟就会被一条腐蚀性的沟渠保护，免受捕食者的伤害。
When the water hits the right level, the baby birds are kept safe from predators by a corrosive ditch.
提前发出的洪水水位上涨警报防止了又一次的重大灾害。
Early warnings of rising water levels prevented another major catastrophe.
在一些地方，水位正以每年一米的速度下降，需要定期加深井并使用更强大的水泵。
In places, the water table is declining at a rate of a meter a year, necessitating the periodic deepening of wells and the use of ever-more-powerful pumps.
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