From the dimensionless governing equations obtained through an adequate selection of dependent and independent dimensionless variables, and the use of spatial discrimination, the dimensionless groups that govern the solution patterns of the heat transfer problem in aquifers with horizontal flow velocity are determined. As a boundary condition on the surface, the cases of constant and harmonic temperature are studied. The emergence of a characteristic length that, in its dimensionless form, depends on the deduced groups, allows the direct determination of the water flow from experimental measurements of the temperature profiles in the classical form of the inverse problem.