A Mexican National Standard, under a workgroup study defined by National Water Commission, is being proposed based on analyzing and integrating a variety of nationals and internationals experiences, related to the establishment of Environmental Flows (EF).

The basin is partitioned to be studied in suitable hydrological subsystems, and then the study's results are integrated into the essential management unit, the whole basin. Different basin's management objectives (considering ecological importance vs. water-use pressure criteria) will be used to determine the basin's main vocation. This National Standard proposes the following levels of analysis: Level zero is primarily under the Tennant approach, enriched by a hydrological variability analysis of the Mexican rivers. Level one is a hydrological approach based on The paradigm of a natural river (Poff et.al. 1997) and The biological condition gradient (USEPA, 2005; Davies & Jackson, 2006); provides EF to regulate the operation of water infrastructure in altered basins. Level two respond to an intermediate detailed need of EF determination (i.e. conflicts among water users; presence of Natural Protected Areas). Level three needs a highly detailed EF determination in order to have a very clear impact assessment for water infrastructure projects. The level zero and one are related to specific reference values. The levels two and three require an holistic method approach such as The building block methodology (King, J. & Louw, D. 1998). The National Standard's procedures resolve the basin issues progressively, in order to get a sustainable water balance, which recognizes the ecosystems as the only water provider.