Head-discharge curves in gated spillways are commonly obtained by means of the application of empirical formulations. The most popular one, recommended by SPANCOLD [1], was developed by the U.S. Army Corps of Engineers [2]. It is based in several experimental campaigns whose results were used to define a chart which provides the value of the discharge coefficient depending on the gate position. This formula does not take into account the effect of side contractions, which depends on the length-height ratio of the bays, as well as the head, the inflow conditions and spillway geometry. Thus, it is necessary to carry out specific experimental tests for every new spillway. The aim of the work is the analysis of the discharge capacity of radial gated spillways. The accuracy of empirical formulations has been studied, and Oliana Dam spillway has been investigated via numerical simulation.