Simulação de qualidade de água com incorporação de análise de incerteza : estudo de caso da bacia hidrográfica do Rio Novo

Abstract

Mathematical models of water quality, which are tools capable of simulating the self purification capacity of watercourses, have gained relevance in water resource management, as they can help prevent future impacts and support decision-making processes within watersheds. However, selecting the parameters and coefficients that make up a model introduces uncertainties into the simulations, as obtaining them can be complex, especially when evaluating water quality. In this context, the combination of uncertainty analysis and mathematical modeling of surface water quality can serve as a valuable tool for water resource management. This study aims to assess the water quality of the Novo River watershed, an important water system in the southern region of the state of Espírito Santo, incorporating uncertainty analysis through the Monte Carlo method into the QUAL-UFMG water quality mathematical model. Groups of 50, 100, 500, 1000, 2000, and 5000 simulations were conducted for the profiles of the following parameters: dissolved oxygen, biochemical oxygen demand, inorganic phosphorus, organic phosphorus, organic nitrogen, ammoniacal nitrogen, nitrite, nitrate, and thermotolerant coliforms. The results of the water quality simulations incorporating uncertainty analysis indicated that the Pardo River and its tributary, the Piabinha stream, do not maintain concentrations compatible with the quality standards defined for DO, BOD, and thermotolerant coliforms in Class 2 rivers along their entire lengths, according to Resolution No. 357/2005 of the National Environmental Council. Additionally, it is noteworthy that the number of simulations conducted did not significantly affect the results, although the cumulative frequency curves became closer to each other as the number of simulations increased