Longitudinal Dispersion along Transient Ground water flow in a finite Aquifer.

ABSTRACT: The distribution of contaminant concentration in the presence or absence of existing contaminants in a finite aquifer is predicted, subject to time-dependent source concentration. Longitudinal dispersion along transient groundwater flow in the homogeneous and finite aquifer is considered, which is initially solute free. This means that some initial background concentration does not exist in the aquifer. The time dependent source concentration is considered in an intermediate portion of the aquifer in a particular time domain and at the other end of the aquifer where the concentration gradient is supposed to be zero. The one-dimensional advective-dispersive equation is solved analytically using the Laplace Transform Technique (LIT). Non-dimensional variables are introduced to reduce the advective term from the parabolic type advectivedispersive equation. The time varying velocity expressions are considered, which represent the realistic situation in the aquifer system. It is assumed that the dispersion is directly proportional to the power ofseepage velocity where power ranges from 1 to 2. Results of the derived anaytical solutions would be useful for benchmarking numerical codes and solutions. They may also be used as preliminary predictive tools for groundwater resource management. Graphical representations, made using MATLAB, reveal the space-time distribution behavior of contaminant concentration. For the uniform source of contaminants, the concentration distribution is also obtained as a particular case.