What process causes well water to move in and out of the well by turning the pump on and off?

The movement of well water in and out of the well as a result of turning the pump on and off is primarily due to the action of mechanical surging. When a pump is activated, it creates a pressure differential that allows water to be drawn into the well from the surrounding aquifer. When the pump is turned off, this pressure is released, allowing the water to return to its original level, and potentially drawing air back into the system if it creates a negative pressure.

Mechanical surging refers specifically to the process of effectively drawing water and then allowing it to rebound or surge back, which can help maintain water quality and manage sedimentation in the well. This is a common practice in well maintenance to ensure that the aquifer remains healthy and productive.

The other processes mentioned do not accurately describe this water movement. Backwashing typically pertains to cleaning filter systems, jetting refers to a technique used to clear sediments or blockages in well screens, and air surging generally involves the introduction of air into the well to displace water but does not describe the pumping action itself. Thus, the correct answer highlights the importance of mechanical surging in the context of pump operation in wells.