Hydrological Basins in Mexico: Divisions and Legal Definition

Abstract

In Mexico, despite the existence of a legal definition of the hydrological basin and an official delimitation of hydrological basins, there are multiple hydrological delimitations. They generate confusion in those who require such information for research or hydrological analysis among other objectives. This chapter focuses on showing the essential features of various hydrological basin delineations that have been proposed for the Mexican territory, pointing out the inconsistencies of the current official delimitation concerning the hydrological basin legal definition in Mexico. The total number of basins in which Mexican territory has been divided is a simple indicator of the variety of criteria considered to perform hydrological delineation. In recent times, this number had varied from 142 to 1474 basins depending on the institution and time when delineations were performed. In the absence of a useful and consensual scientific hydrological delineation, current hydrological delimitations could be systematically identified with names, codes, purposes, and possibilities of use. This regulation could reduce confusion and facilitate the proper application of each hydrological division. Official river basin delimitation in Mexico is applied to calculate surface water availability and in turn to legally confer water rights. However, such delineation does not comply with Mexican legal definition of the hydrological basin. Since official and legal precepts must be consistent, a measure to harmonize this inconsistency is convenient. Changing precise delimitation is a primarily technical and administrative task with possible legal implications. In this sense, it appears more convenient to modify the legal definition to match official hydrological basin delimitation.