When the pump in your well is in operation, the water level in the aquifer around the well is lowered. The area affected by this pumping is greatest next to the well and gradually decreases as the distance away from the well increases. This area is known as the wellhead area of influence. Ground water flow in the area of influence is generally toward the well. Therefore, any contaminants present in the area may move toward the well. It is for this reason that proper handling, application and storage of chemicals or fertilizers is important to protecting your source of drinking water.