Groundwater is water that permeates the ground whether by precipitation or from surface waters such as lakes and rivers. Water that seeps into the ground is first used by various biotic factors such as root systems of plants. Yet, ample water will continue to move downward through porous layers, filling empty spaces until it reaches an impervious layer. This area of porous and permeable rock and soil surrounded by an impermeable layer is called an aquifer. Aquifers are classified as either confined or unconfined. Groundwater stored in aquifers can be found at various depths anywhere between a few feet to several hundred feet below the Earth’s surface. The rate of recharge of an aquifer depends on numerous factors including, size, depth, permeability, whether it is confined or unconfined, water demand and amount of water available. Groundwater is commonly extracted using wells, yet also discharges naturally forming springs or into lakes and rivers. It is estimated that roughly 50% of people in the US rely on groundwater for multiple every-day uses. Groundwater quality is threatened by agricultural and urban runoff, industrial waste effluent as well as salt water intrusion from over extraction.