Figure 1. In the unsaturated zone, pore spaces contain air; hence, no groundwater can be pumped from this zone. Usable groundwater occurs in the saturated zone, where pore spaces are completely filled with water.
shallow well or a deep well , originates and is replenished (recharged) by precipitation.
Groundwater is part of the hydrologic cycle, originating when part of the precipitation that falls on the Earth's surface sinks (infiltrates) through the soil and percolates (seeps) downward to become groundwater. Groundwater will eventually come back to the surface, discharging to streams, springs, lakes, or the oceans, to complete the hydrologic cycle.