PREVIOUS STUDIES The Comisión Nacional del Agua has calculated the flood discharge of the portion of Arroyo Alamar watershed not subject to regulation by Morena and Barrett Dams. The study utilized the following statistical methods: Gumbel Gumbel II Normal distribution. The analysis concluded that the normal distribution was more representative of the gaged data (14 yr). For the delineation of the federal zone, the study calculates a design discharge of 800 m3/s, which is comprised of two parts: The 550 m3/s discharge pertaining to a 50-year storm for the flood runoff generated exclusively downstream of Barrett Dam. The discharge of 250 m3/s corresponding to the spilling of Barrett Dam. The ratio of discharges (550 m3/s / 800 m3/s) was calculated based on the ratio of drainage areas. A similar study was commissioned the following year (1994). The discharge to be used in the delineation of the federal zone of Alamar Creek was determined to be 550 m3/s, corresponding to a 10-yr return period. The difference between these two studies, for the same purposes, is marked. The first study assumes the normal distribution as valid, a return period of 50 yr, and considers that a fraction of the total discharge, calculated by means of a ratio of tributary areas, is spilled from Barrett Dam. The second study considers the Gumbel II distribution as valid, a return period of 10 yr, and does not consider the spilling of Barrett Dam.

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