Groundwater Dynamics in a Sandy Unconfined Aquifer

Abstract

Groundwater dynamics in a sandy unconfined aquifer have been investigated through laboratory experiments and numerical modelling. The laboratory experiments on the propagation of groundwater waves have yielded new insights into underlying physics. Numerical models have been developed to consider some aspects of groundwater dynamics such as the influence of seepage face and meniscuses formation, hysteresis effects, unsaturated flow dynamics, and porous media deformation. The laboratory data has then been used to verify numerical models and to examine their prediction capabilities. New laboratory data from sand flume experiments for an idealized coastal aquifer forced by a simple harmonic forcing across a vertical boundary provided detailed measurements of the piezometric head very close to the interface. The data helped to consider the processes occurring near the boundary condition, particularly with respect to meniscus and seepage face formation during the falling tide. A numerical solution of the Richards’ equation was developed to model the influence of seepage face formation and meniscus suction and was evaluated against the data. The model-data comparisons show good agreement with the pore pressure behavior high above the water table, but are sensitive to the choice of moisture retention parameters in the model.