Avalição da retenção de sedimentos em suspensão em empreendimentos hidrelétricos na Bacia do Alto Paraguai

Abstract

The implementation of reservoirs affects the transport of sediments in rivers and can cause geomorphological and environmental changes, especially in situations where dams are built upstream of flood plains, such as the Pantanal. Therefore, it is necessary to understand the sediment load retained to predict possible impacts. Therefore, this article aims to: Investigate whether the main empirical methods are good alternatives for estimating the efficiency of sediment retention in the Hydrographic Region of Paraguay; Develop regional empirical models to predict retention from the ventures in operation; Compare predictive capacity Efficiency of retention between regional models and main classic models; and Assess the effects of hydroelectric developments in operation on sediment retention. For this purpose, characteristics of the influential reservoirs in the transport of sediments were extracted and the retention efficiency was calculated from suspended sediment load data. After that, Churchill and Heinemann models were applied to estimate retention efficiency. Then, a local empirical model was developed based on the observed sediment retention data and reservoir characteristics and compared with the empirical models previously applied and, finally, potential impacts of the observed retentions in the Basin were analyzed. It was demonstrated that the empirical methods of Churchill, Heinemann and the local sediment retention efficiency models for small reservoirs cannot be used indiscriminately in the Hydrographic Region of Paraguay due to high estimation errors. The local empirical models developed are composed of the variable drainage area associated with the Churchill sedimentation index and the relationship between storage capacity and Brune's annual water intake. In addition, the sediment retention observed in the reservoirs associated with the possibility of installing future projects in the basin may have an effect on the Pantanal and the Basin in general.