Mathematical model as a management tool to analyze organic matter self-purification in reservoirs.

Abstract

A mathematical model to analyze the self-purification potential of organic matter in reservoirs was developed, seeking to constitute a potential water management tool for easy application. Therefore, it was considered the input of organic matter into the watercourse, its sedimentation, decomposition and its output downstream, as well as the oxygen input through the flow and through re-oxygenation, its consumption by microbial activity and its downstream exit. The model was validated using data of Tietê river and applied using data of Salto Grande reservoir, both located at São Paulo State, Brazil, considering different scenarios of biochemical oxygen demand (BOD), dissolved oxygen (DO), water inlet flow and reservoir water volume. The results show that organic matter is decomposed faster in the first 12 hours of water travel; moreover, self-purification efficiency is better with a greater volume of water in the reservoir. The model is quite representative to study different self-purification scenarios in dammed areas, concluding that the developed model, being tested and improved, can already contribute to the management of reservoirs, with the advantage of having a simple application.