Groundwater
[Wikipedia] The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as, the upper level, below which the ground is saturated.
[EnvThes] upper surface of the zone of saturation, below which all available pores in soil and rock are ﬁlled with water.
Water table