Modeling of the time evolution of a solute plume in a heterogeneous porous formation has often focused on low-order spatial concentration moments calculated in comprehensive field experiments in which a plume is sampled synoptically at successive stages of its postinjection development. Assumptions of stochastic nature usually have been invoked to derive equations that predict the time dependence of these spatial moments and permit their interpretation in terms of field concentration data. In this paper, expressions for the low-order spatial moments are derived on the basis of a purely dynamical formulation of plume motion in terms of the solution of the autonomous ordinary differential equation determined by a steady fluid velocity field. The equations derived stress the importance of spatial interdependence between the (arbitrary) initial state of a solute plume, as defined by its concentration field, and the subsequent displacements of moving spatial points determined by a groundwater velocity field. ¿American Geophysical Union 1994