Design Floods of the Cointzio Dam, Mich., Mexico with Analysis of Historical Flows

The Cointzio dam is located in the State of Michoacán, Mexico in Hydrological Region number 12 and has inflows mainly from the Rio Grande; Its importance lies in the fact that the water stored in this dam has irrigation and drinking water from nearby locations as its main uses. In this study we used the historical daily average flows records derived from the operation of the reservoir vessel, reported by the National Water Commission, which is the operating agency to update the design floods for the spillway of this reservoir using the Method of the Institute of Engineering with the proposal of a base time estimated from the review of the most important maximum floods that have historically happened in the study site. An analysis of instantaneous maximum flows registered in the available gauge station was made by comparing one of the most important events with the average daily flow reported on that date in order to obtain a factor to propose a maximum peak flow to the daily flood generated, trying to keep the volume at the center of the hydrograph; this peak design flow was compared with that obtained using regional factors and the historical average of the maximum instantaneous flows, selecting the most unfavorable. Additionally, the floods obtained by the spillway were routing to review the hydrological operation of the dam, which involved obtaining the maximum elevations reached, in order to compare them with the maximum extraordinary water level, in addition to the maximum discharged flows . With the flood routings, the selected base time was verified since the full definition of the branch of descent of the outflow hydrograph depends on it. The analysis was made for design floods corresponding to return periods of 50, 100 and 10,000 years. The discharge policy for the spillway was reviewed and adjustments were made when exceedances of the maximum water elevation level were observed.