Abstract
In general, a natural aquifer has a hydrogeologically non-uniform structure. The movement of pollutant in groundwater is affected by such structural properties while it is transported by local advection and microscopic dispersion. The macroscopic dispersion grows linearly with respect to the travel distance or the travel time at the initial stage after the pollutant is released, and then, asymptotically converges to a constant value through the transient stage. It is important for the practical applications to know how such macroscopic dispersion grows when the prediction of pollutant spread is required in the transient stage.
In the present study, a method for judging the convergency of macroscopic dispersion is discussed for the analytical and observed average concentration by the numerical simulation. The χ2-test for convergency in the macroscopic dispersivity is applied. Besides, an evaluation procedure for the auto-regressive parameters in the generating model of the random field of permeability is proposed, for the case in which the macroscopic dispersion is estimated to be still in the growing stage. The characteristics of the proposed method is examined through the applications to synthetically generated random fields of permeability.
