Simulation model of DO and BOD integrating river and reservoir applied to the Tietê River

ABSTRACT

A simulation model of DO and BOD combining rivers and reservoirs, was developed in the software Microsoft Office Excel and used in the Tietê river, stretch between Pirapora do Bom Jesus and Salto, known to be polluted due to the receipt of the remaining organic load contribution to Metropolitan Region of São Paulo. The calibration used to monitored data and optimization tools. They were simulated 12 scenarios characterized by the combination of the variables: discharged flow (700, 411 and 130 m³/s), level of the reservoir (691 and 688 m), and input concentration of BOD to Pirapora reservoir (37 and 56 mgO₂/L). With these analysis of the scenarios was possible to evaluate the impacts of reservoir operation on the water quality of the Tietê River downstream of this dam. The results indicated that the water quality to input on reservoir protrudes towards the operational aspects. Reduce the contribution that organic load refers to a long-term planning. A short-term alternative is to minimize the impacts operate with low discharge reservoir (130 m³/s), while keeping the normal level (691 m). Thus, when the input concentration of BOD is high (56 mgO₂/L), the stretch between Pirapora do Bom Jesus and Cabreúva is anoxic and the region of Salto presents DO and BOD concentrations of 3 and 20 mgO₂/L, respectively. When normal (37 mgO₂/L), is not found anaerobic conditions throughout the simulated stretch and the region of Salto presents concentrations of 6 mgO₂/L and BOD equal to 17 mgO₂/L.

Keywords:
Water quality; Organic load; Tiete river; Reservoirs operation