Proposal of a system‐based model to simulate river water quality in São Paulo state – Brazil

In order to help watershed committees improve Basin Planning, the purpose of this study is to propose to apply system dynamic models to understand watershed conditions and to evaluate the main aspects of human impact on water quality for Brazilian rivers.

This work makes use of the energy system language to propose a system modeling. The river is longitudinally modeled as a web of inter‐connected compartments and individually described for each control volume by differential equations.

The model considers particular and significant characteristics such as turbidity and sedimentary organic matter content of São Paulo State rivers and results in ordinary differential equations that are adequate to the Brazilian water quality database. It is expected that simulation will provide the longitudinal and temporal dynamic behavior of total phosphorus, biomass, dissolved oxygen, organic matter, benthonic organisms and fishes that will be used to evaluate future scenarios and to identify sustainable public policies for the Basin.

Water quality simulators available in developed countries are strongly dependent on an extensive series of observed data, most of which are not available for the Brazilian rivers. The model here proposed is adapted to the current Brazilian water quality monitoring system, which provides historic series of observed data of pollution sources and water quality parameters along the stream.