We examine theoretically the mechanics of intensive pumping of groundwater from a layered soil. The soil system is assumed to consist of three horizontal layers where a very soft and highly impervious aquitard is sandwiched by two hard and highly porous aquifers. Water is pumped from the bottom aquifer through a vertical well. Attention is focused on the case where the pumping rate is so strong that the ground subsidence, contributed mainly by the soft aquitard, is comparable with the typical layer thickness. By a perturbation theory and the use of lagrangian coordinates, we deduce an approximation which incorporates the quasi-three-dimensional scheme of Hantush & Jacob for the pore pressure, and the one-dimensional finite strain theory of Gibson et al. for the soil consolidation. Unlike the approximations prevailing in hydrological literature, it is shown in particular that the pore pressure is nonlinearly coupled to the soil deformation and that the total stress is not necessarily uniform in depth. Hysteretic subsidence and the associated variations of soil parameters due to various forms of cyclic pumping or recharging are discussed.