By 1950, though, human activities had started to make an impact. Then, the water level began to drop at a rate of 30 centimeters (about a foot) each year.
到1950年,人类活动开始产生深远影响。那时,水平面开始以每年30厘米的速度下降。
2
Then, the water level began to drop at a rate of 30 centimeters (about a foot) each year.
那时,水平面开始以每年30厘米的速度下降。
3
The disorder produces foot deformities, dropfoot and other difficulties that can be corrected surgically.