Groundwater is water that seeps into the Earth’s surface through soil and cracks in rocks until it reaches a non-porous layer of rock and cannot easily move. Water begins to collect above this layer in an aquifer or permeable soil or rock that allows the passage of fluids. Groundwater is naturally recharged by rain water, snow melt, or leaks from lakes and rivers that seep down from the land surface. Recharge can also be derived from human water supplies when supply systems leak or crops are over-irrigated. Groundwater is naturally discharged into springs, rivers, swamps, and lakes. Groundwater supplies more than half of the US population’s water supply, particularly in rural areas. This water is pumped from the ground and is used for drinking water, irrigation, and other uses. The water table, or level of groundwater, rises and falls as recharge and discharge amounts vary.