In this paper we show the results when making a comparison between the calculation of availability of surface water following the methodology of the Mexican Official Standard NOM-011-CNA-2000 and in situ measurements made in the Blanco River sub basin, which belongs to the Papaloapan River, with the objective of linking environmental and hydrological aspects quantitatively. Despite the significant difference in scale for calculation and measurements, the comparison is quite good, and illustrates the objective: to have quantitative elements that consider the environment in a water balance.