Gull's theory for rotating hydraulics is applied, as a reduced gravity model, to the surface inflow through the Strait of Gibraltar into the Mediterranean as it is shown that rotation is mostly important east of Tarifa Narrows where only the upper layer is active. Details of the flow depend on the volume flux, Q, and on the potential vorticity of the inflow. We examine two extreme cases for this. In both examples the model predicts that supercritical inflow separates from the north share about half way between Tarifa and Gibraltar, so that at Gibraltar the flow is separated. The comparison of (i) conditions for criticality, (ii) separation widths and (iii) interface depths and velocities in midstrait, between this 2D model and the ID models of Farmer and Armi and of Bormans and Garrett suggests that the use of a simple 1D model is appropriate for the Strait of Gibraltar for both subcritical and separated supercritical flows. However, for the latter, the prediction of the point of separation and of the interface depth using the 1D model requires allowance for the effect of rotation.