Groundwater that soaks into the ground after rain. It is replenished mostly by rain. If there is less rain than use of the water, the water level will decrease. If the water use is stopped, it may take thousands of years to completely replenish the groundwater. Groundwater is the water found underground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations of soil, sand and rocks called aquifers.