A city worker is trying to dig to reach the water table. She knows the unsaturated zone in the area is four feet thick and the saturated zone is another five feet thick before an impermeable granite layer is reached.

How deep will she have to dig to reach the water table?

two feet

four feet

five feet

nine feet

four feet

B. Four feet

Explanation:

Water table is definied as the level below which water is saturated within an underlying rock. Therefore, to reach the water table, only four feet excavation is necessary. This is also the reason that it is called as saturated zone because it is fully filled with water and has no air trapped. On the other hand, unsaturated zone has air bubbles and the amount of holding water is lesser to be used for water extraction. Hence, the city worker would reach the water table.

PS: In short, saturatd zone is already the groundwater.