An analytical model for stream-stimulated hydraulic communication in vadose and saturated zones

A conceptual model was established to study the patterns of flow in vadose and saturated zones system induced by a prescribed boundary. Richards’ equation was adopted to describe groundwater flow in the vadose zone. Laplace transform and cosine Fourier transform were chosen to derive a semi-analytical solution of the governing equations. A finite-element numerical solution built with COMSOL software was used to test the semi-analytical solution. The buildups of the hydraulic head were investigated for different hydraulic parameters. Some noteworthy conclusions were obtained. The vadose zone parameters (constitutive exponent (κD) and specific yield (Sy)) have a significant effect on the buildups in the vadose zone and saturated zone. A larger κD value and smaller Sy value both lead to higher buildups in the vadose zone, while a larger κD value and a larger Sy value resulted in smaller buildups. As for the specific storage (Ss) of the saturated zone, the influence on buildup is more obvious in the saturated zone rather than in the vadose zone. The analysis further indicates that Media Anisotropy (Kz/Kx) value exhibits opposite influences on the hydraulic head in vadose and saturated zone. The present solution offers a valuable basis for further research of groundwater recharge and better design of MAR engineering.