In the southern summer of 2017, the coastal El Niño phenomenon occurred in Peru. This type of event is recurrent in this region and due to its intensity, floods occurred in the city of Piura and in the Lower Piura Valley, due to the overflowing of the river of the same name. Scenarios like this put the structures within the riverbed at risk. In order to prevent and provide a warning system that allows timely evacuation of the areas at risk, it is necessary to know the flows that occur in the river. However, there are reasonable doubts about the reliability of the gauges in Los Ejidos Dam, located upstream of the city. This is because the basin's early warning system predicted maximum flows of 2900 m3/s on March 26, 2017, based on rainfall and flow data upstream of Los Ejidos, and finally the flow measured at the dam was 3468 m3/s. At that time the uncertainty was established as to whether the forecast model was out of balance or whether the measurements at the dam had calculation errors. This article presents the calculation of the flows in Los Ejidos Dam based on the collection of data recorded in the dam by the operator, Chira Piura Special Project (PECHP), during the period from January to May 2017, strictly following the existing literature, as well as the operation manuals. From the results obtained, it can be seen that the structure works alternately under a submerged and non-submerged regime, in addition to the fact that the greatest contribution to the flow comes from the free spillway, followed by the floodgate spillway and the cleaning channel. On the other hand, the flow obtained from the levels recorded during the El Niño 2016-2017 phenomenon differs by 16% from the maximum value reported.