Modelación de la calidad del agua del río Tula en el Estado de Hidalgo, México.

The central objective of this work is to model the quality of the water of Tula River, from the centralemitter to their confluence with the Endhó dam. It was evaluated during two years, considering a length of 50 km in4 zones and 35 sites of sampling. The central emitter contributes to the greater amount of organic matter, waterwithout treatment of the City of Mexico and co urbane zone. The values of DBO varied from 1.16 up to 486.81 mgO2/L; the oxygen dissolved between 1.52 and 5.82 mg/L, this implies affectation for the development of the aquaticlife. The alkalinity exceeded the ecological criteria of quality as a source of potable water with value of 458.01 mg/L.The fats displayed variations from 0.9 mg/L up to 18.1 mg/L and ammonia cal nitrogen outside the limits establishedfor protection of the aquatic life with values from 0.09 a 64 mg/L; nitrates (6.24 mg/L) and nitrites (0.5-1.304 mg/L)exceed the ecological criteria. The metals cadmium, lead, iron, manganese and zinc are in concentrations over thepermissible rank and in some sections mercury presence was reported. The fecal coliforms were detected in valuesfrom 2.1 x104 up to 2.40 x1011 NMP/100 milliliters. In general, the toxicity in the residual water unloadingdemonstrated that all appears of moderate to high. Only there were three monitored stations (19%) with excellentquality, 3 smaller or equal DBO5 to mg/L, which is considered like water no contaminated by biodegradable organicmatter.