ARTICLE 231:

The areas of availability referred to in article 223 of this Law (LFD: Art. 223), shall be determined in accordance with the following:

Cp + Ar + Im

Dr=

Uc + Rx + Ex + Ev + ?V

Where:

Dr = relative availability.

Cp = Average annual volume of natural runoff.

Ar = Average annual runoff volume from the upstream basin.

R = Annual volume of returns.

Im = Annual volume of imports.

Uc = Annual volume of surface water extraction.

Rxy = Current annual volume committed downstream.

Ex = Annual volume of exports.

Ev = Annual volume of evaporation in reservoirs.

?V = Annual volume of storage variation in reservoirs.

The annual volume of returns is determined by capacity of departures of the volumes that return to the drainage network of a basin.

The annual volume of evaporation in reservoirs is determined from the measured evaporation sheet, applied to the free surface of the exposed water, in natural or artificial reservoirs.

The annual volume of storage variation in reservoirs is determined by the difference of the final volume, minus the initial volume (final V ? initial V), of each particular year.

The variables that make up the formula provided for in this section, except Ev (annual volume of evaporation in reservoirs) and ?V (annual volume of storage variation in reservoirs) will be determined in terms of the mandatory method provided in the Official Mexican Standard NOM-011 -CONAGUA-2000 that establishes the specifications and the method to determine the annual average availability of national waters.

If the Official Mexican Standard indicated in the previous paragraph is modified, for the purposes of this article, NOM-011-CONAGUA-2000 will continue to be applied.

The National Water Commission shall publish annually in the Official Journal of the Federation (Diario Oficial de la Federación), no later than the second month of the fiscal year in question, as an administrative facility, the values ..of each of the variables that make up the aforementioned formula.

The result obtained from the formula provided in this fraction will be located within the following ranges to determine the availability zone that corresponds to the basin:

Dma

Idas=

(R-Dnc)

Where:

Idas = Availability index.

Dma = Average annual availability of groundwater in a hydrogeological unit.

R = Annual average total recharge.

Dnc = Committed natural discharge.

The variables that make up the formula provided in this section will be determined in terms of the mandatory method provided in the Official Mexican Standard NOM-011-CONAGUA-2000 that establishes the specifications and the method to determine the average annual availability of national waters.

If the Official Mexican Standard indicated in the previous paragraph is modified, for the purposes of this article, NOM-011-CONAGUA-2000 will continue to be applied.

The National Water Commission (Comisión Nacional del Agua) shall publish annually in the Official Journal of the Federation (Diario Oficial de la Federación), no later than the second month of the fiscal year in question, as an administrative facility, the values ..of each of the variables that make up the aforementioned formula.

The result obtained from the formula provided in this fraction will be located within the following ranges to determine the availability zone that corresponds to the aquifer:

The provisions of this section are without prejudice to the provisions of the previous sections of this article.

Regardless of whether taxpayers can determine the availability zone corresponding to the hydrological or aquifer basin where the extraction is carried out, the National Water Commission (Comisión Nacional del Agua), as an administrative facility, will publish no later than the third month of the fiscal year in question, the availability zone that corresponds to each hydrological and aquifer basin of the country.