A proposal to integrate the legal definition and official delineation of watersheds in Mexico: eight model case studies

Abstract

A hydrological basin is established as a geographic frame to officially determine surface water availability and is basic to confer or deny water rights. In Mexico, the legal definition of a hydrological basin is confusing and inconsistent with the official basin delineation published by the authority. This situation is demonstrated through the analysis of eight study cases located in Hydrological Region 10 Sinaloa. A proposal to define the legal term of hydrological basin, ensuring its consistency with official delineation of hydrological basins is presented. Geographic analysis was performed using QGIS software, by using official sources of Mexico and worldwide data bases. By law, in Mexico a water parting is defined as a borderline of maximum elevation. Nevertheless, the legal definition fails to explain hydrologic basin official boundaries where the basin limit is the location of a hydrometric station. Besides, the presence of this equipment does not mean that a waterbody exists in a hydrological basin, or that the delimited basin is an autonomous differentiated unit, as it is required by the legal definition. Other inconsistencies are presented dealing with the presence of inland water bodies as watershed limits and with groups of independent watersheds incongruously considered as a single basin. An amendment is proposed to harmonize this situation, with a minimum of changes in policy documents. The method proposed can be useful to analyze similar situations in other countries where discrepancies between the legal and official definitions of watershed delineation are also observed, or in countries where no official watershed definition has been established.