A three dimensional model elucidates connection between observed internal hydraulic characteristics of the Bosphorus flow and channel configuration. A typical two-layer, quasi-steady exchange flow system is shown to be hydraulically adjusted within the strait by a series of morphological features. Three successive hydraulic controls occur within the southern 10 km zone: first near the southern exit due to convex bending of the channel, then at the southern sill and at the constriction. Finally, the exchange flow system experiences another hydraulic control at the northern sill near the Black Sea entrance of the strait. The upper and lower layer flows exiting from the strait at both ends with currents of similar to 1.0 m s(-1), layer depths of similar to 10 m and g' similar to 0.1 ms(-2) thus impose maximal exchange conditions.