Modelling of pumping from heterogeneous unsaturated-saturated porous media

Practising civil engineers often use analytical solutions to estimate pumping rates and drawdowns associated with dewatering systems. These solutions are usually based on assumptions of predominantly horizontal flow as well as of homogeneous permeability and compressibility of the soil. The disadvantage of these methods is that they are based on the assumptions of saturated flow, despite the fact that after intensive pumping, more permeable layers of an multi-aquifer system might desaturate. Engineers need more versatile modelling tools if they are to design successful dewatering systems. For this reason, a finite element code which takes into account soil desaturation has been developed by the writers. The present paper investigates the problem of well drying when water is continually abstracted for a certain time period in a multi-layered aquifer system. The analyses focus on the influence of heterogeneity induced by the soil layering.