Fig. 12. Discharge scenario

62 Hydrodynamics – Natural Water Bodies

Fig. 11. Velocity contours of Coatzacoalcos River (rain and dry season) over time

the influence of urban areas where such facilities industry are seated.

This section presents some of the simulated parameters. Initially we describe the simulation scenario solved to provide a better idea and understand clearly what the simulations are

To assess the water quality in Coatzacoalcos River, a representative discharge scenario was initially defined, highlighting the main activities and characteristics over this area (Fig. 12). The idea was study the river environmental behaviour, influenced by the oil activity developed on this area, six discharges where located representing the industrial activity and

The discharge conditions for every simulated water quality parameter are presented in

**Discharge Temp. (ºC) DO (mg/L) BOD (mg/L) Faecal Col.** 

**Minatitlan** 26.70 3.70 290.71 21,5000 **Refinery** 25.70 3.70 190.86 21,3000 **Uxpanapa R.** 24.70 3.70 190.70 21,7000 **Nanchital** 27.70 3.70 290.43 31,5000 **Pajaritos P.C.** 26.70 3.70 290.83 22,4100 **Coatzacoalcos** 25.70 3.70 110.60 21,4300

**(NMP/100 ml)** 

**4.4 Modeling of pollutant transport** 

**4.4.1 Simulation scenario** 

Table 3. Discharges conditions

representing.

Table 3.

The following figures show the model results for these water quality parameters.

Fig. 13. Temperature simulations over time

A Study Case of Hydrodynamics and Water Quality Modelling: Coatzacoalcos River, Mexico 65

The solution obtained for the two-dimensional Saint-Venant and A-D-R equations using an Eulerian-Lagrangian method has great versatility, obtaining consistent and satisfactory results for different types of flow and open channel conditions. The considered scheme provides numerical stability that avoids numerical oscillations of the obtained solutions and also allows significant larger time steps (Δt). The combination with the Eulerian solution for

About the hydrodynamics study of Coatzacoalcos river, it was determined that the river behaviour is influenced by several factors, being the most important the hydrological aspect, which varies depending on the time of the year. Because of this, it was observed that dry season presents an important tide penetration towards the mainland of the river, while for rain season when the river flow increase, the penetration is less significant and the water

On the other hand, the pollutants transport is dominated strongly by the hydrodynamics, and the difference for the two simulated seasons was observed. This simulation shows higher concentrations and also a more significant dispersion in dry season, because the tide penetration occurs intermittently upstream and downstream in the area near to the river mouth. While for rain season there is no significant contaminant dispersion, with a local

Thus, a solution algorithm has been proposed to the study open channel hydrodynamics, which together with the A-D-R equation solution allows the study of transport,

diffusive terms is always guaranteed satisfying the C-F-L condition.

mainly flows downstream to the mouth in the Gulf of Mexico.

effect of the simulated discharges.

Fig. 16. Faecal Coliforms simulations over time

**5. Conclusions** 

Fig. 14. Biochemical Oxygen Demand simulations over time

Fig. 15. Dissolved Oxygen simulations over time

Fig. 16. Faecal Coliforms simulations over time
