Modeling and analysis of sediment discharge in three tributaries of the Mourão River basin, Brazil

The transport of sediments in river systems has significant environmental and economic implications, affecting water quality, aquatic ecosystems, and the operational lifespan of hydraulic structures such as reservoirs. This study quantified and analyzed sediment discharge in three distinct river sections within the Mourão River basin in Paraná, Brazil, by applying and comparing various mathematical models. The three sampling sections were established on the Campo River (Section 1), the Mourão River (Section 2), and the Sem Passo River (Section 3). Bedload sediment discharge was calculated using the methods of Einstein (1942) with a Peter-Meyer modification, and Duboys (1879) and Zeller (1963). Suspended sediment discharge was estimated using the models of Yang (1973) and Righetto (1998) and compared with experimental results from total suspended solids analysis. Hydraulic characterization, including the development of rating curves and the calculation of the Froude number, was performed to understand the flow regime. The results indicated a subcritical flow regime (Fr < 1) in all three sections, characteristic of relatively slow-moving water. The Duboys (1879) and Zeller (1963) model was only applicable to Section 1, a smaller channel, as it yielded non-representative results for the larger perimeters of Sections 2 and 3 under the observed low-flow conditions. In contrast, the Einstein (1942) approach with the Peter-Meyer modification proved more robust, providing viable estimates for all sections. A strong correlation was found between the Froude number and the sediment discharge predicted by the theoretical models. This study highlights the critical importance of selecting appropriate models based on the specific hydraulic and geomorphological characteristics of the river channel and underscores the complexity of accurately predicting sediment transport. Keywords: Froude number, mathematical modeling, Mourão River, rating curve, sediment transport.