What is the residual drawdown of a well defined as?

The residual drawdown of a well is defined as the water level below the normal level that remains after the well has been pumped and the pump is turned off for a certain period. This drawdown represents the reduction in the water level caused by the extraction of water from the well, indicating how much the groundwater level has dropped due to the pumping activities. When the well is allowed to recover, the observed water level may rise, but it often does not return to the original normal level immediately, resulting in residual drawdown.

In contrast, water levels that are stable during operation are indicative of balance between the water being extracted and the water being replenished, rather than the residual effects. Seasonal variations in groundwater levels can be influenced by factors such as rainfall and climate changes, which do not pertain specifically to the effects of pumping. Additionally, water level above normal after pumping would not reflect the conditions indicative of residual drawdown, as this implies a situation of recovery rather than a sustained reduction. Understanding residual drawdown is crucial for assessing the sustainability of groundwater resources and the impacts of pump operations.