Final answer:
Groundwater originates from precipitation, which soaks into the ground, filling the spaces in soil and rocks, and makes its way into aquifers.
Step-by-step explanation:
The source of groundwater is precipitation. Precipitation includes all forms of water that fall from the sky, such as rain, snow, sleet, and hail. When precipitation falls on the land, it may flow across the surface as runoff, but a significant amount infiltrates the ground and fills the spaces and cracks within soils and rocks, becoming groundwater. This groundwater can then flow into aquifers, which are underground layers of rock or sediment that can store vast amounts of water, sometimes for thousands of years. Groundwater can be a source of freshwater for human use and is critical for sustaining both ecosystems and agriculture. It also plays a role in recharging rivers, streams, and lakes.