In well hydraulics, what does the term "drawdown" refer to?

The term "drawdown" specifically refers to the difference between the static water level—the level of water in the well when it is not being pumped—and the pumping water level, which occurs when water is actively being drawn from the well. This measurement is crucial for understanding the behavior of the aquifer and the well’s performance during pumping operations.

When a well is pumped, water is removed from the aquifer, causing the water level to drop; this drop is what is quantified as drawdown. Monitoring drawdown helps determine the efficiency of the well, the aquifer's capacity, and sustainability of the water extraction. A significant drawdown can indicate that the well is not able to maintain adequate water levels, which could affect water supply and well longevity.

In contrast, the total depth of the well is a physical measurement of how deep the well extends, while the rate of water flow in the well pertains to how quickly water can be drawn out, and the volume of water stored in the aquifer refers to the overall capacity of the underground source. These concepts relate to well performance but do not define drawdown itself.