Groundwater is found underneath the water table, where it fills in the pores and spaces between rocks, soil, clay, and sand. Pockets of groundwater found within the earth are referred to as aquifers. Wells are dug into the earth in order to pump water up towards the surface for human use.
Groundwater is a major source of freshwater in the world. Almost half of all groundwater pumped in the US is used for agricultural purposes. Aquifers can exist for 100s of years, and are constantly refilled as precipitation soaks into the soil. However, if too much water is used before the aquifer has a chance to recharge, it can become depleted. Depleted groundwater shows up in the way of dry wells, and lakes and rivers drying out and becoming shallower.
