Drawdown in Compressible Unconfined Aquifer

Elastic response of unconfined formations to pumping is considered. The nonequilibrium drawdown equation for a partially penetrating well discharging at a constant rate in an unconfined anisotropic aquifer of finite thickness is derived for the early period after pumping commences when abstraction of water is entirely due to the elastic deformation of the aquifer. This early stage precedes that described by Dagan's equation when the aquifer yields water by gravity drainage and desaturation. Solutions for the early drawdown, and for the late drawdown, have been computed and are given in the tables. Type curves plotted from the tables presented may be used for the curved-matching procedure to analyze pumping test data.