The present edition, while maintaining the level of information of the original Manual, seeks to be more compact and pleasing to the eye. That is to say, it is a reference work directed especially to the technicians who work in the area, offering some theoretical difficulty for the more casual reader or less familiar with the subject.In this Manual for the evaluation of slope stability of the Castellanos reservoir from the calculation of the safety factor, the criteria usually adopted by geomechanics are presented, seeking to simplify the procedures and ease of application.We ask all users of this Manual to collaborate in the updating and permanent improvement of the text, sending suggestions, comments and criticisms to the address below.