Analytical Study of Unsteady Nested Groundwater Flow Systems

Abstract

Two analytical solutions using segregation variable method to calculate the hydraulic head under steady and unsteady flow conditions based on Tóth's classical model were developed. The impacts of anisotropy ratio, hydraulic conductivity (K), and specific yield (s) on the flow patterns were analyzed. It was found that the area of the equal velocity region increases and the penetrating depth of the flow system decreases at steady state with anisotropy ratio increases, which is defined as ε=Kx/Kz. In addition, stagnant zones can be found in the flow field where the streamlines have opposite directions. These stagnant zones move toward the surface as the horizontal hydraulic conductivity increases. The results of the study on transient flow indicate that a relative increase in hydraulic conductivity produces a positive impact on hydraulic head and a relative enhancement in specific yield produces a negative effect on hydraulic head at early times.