A field scale study of pumping-induced drainage and recovery in an unconfined aquifer

Analogous to the pumping test observations, the response of the moisture content profile during recovery is essentially an upward translation. While the hydraulic head levels recovered nearly to their pre-pumping elevations, the moisture content profiles stabilized approximately 0.20 m below their pre-pumping positions. This recovery differential leads to a capillary fringe compression that converted excess storage during pumping into storage deficit during recovery. In contrast to the significant radial variation of the capillary fringe extension during pumping, the capillary fringe compression is relatively uniform out to at least 15 m during the late recovery stage. The recovery deficit and entrapped residual air observed below the upward translating transition zone are strong indications that significant hysteretic processes are occurring at the field scale.