The meaning of the regime channels is explained and the prominent ways of their investigation are outlined. A particular attention is given to the determination of regime channels by the current "rational" methods: the present paper is the authors' contribution to this approach. The computational method suggested herein rests on the regime channel formation criterion, which is revealed on the basis of the Second Law of Thermodynamics and the Gibbs' equation. The (usual) consideration of the transport rate formula is replaced by the authors' regime width relation; thus the need for the beforehand knowledge of the transport rate is eliminated. The validity of the relations derived is tested by comparing them with the field and laboratory data of various sources.