Estimativa da descarga sólida e granulometria do sedimento de fundo do Rio Iguatemi

Abstract

The silting is a really common problem on the water courses, being the biggest reason the anthropic erosion caused by improper use of the soil and deforestation of vegetation near the rivers. This erosion causes several negative consequences for the water course, for exemple, the decrease of the water quality for consumption, impairing of aquatic life, causes floods and reduces the lifespan of hydroelectric reservoirs. For this reason, the enterprise Itaipu Binacional has a continuous monitoring of the tributaries of Paraná River to have the control of the amount of sediment that is depositing on its reservoir. This sediments can be classified as: suspended solids, dissolved solids (that don’t deposit), and as bottom ones (composed by gross particles, which never leave the bottom, and the jumping particles, that can be on the bottom or suspended), being both types responsible for reducing the lifespan of hydroelectric plants. This paper has the purpose to compare the values of the solid bottom discharge estimated by the direct method (sampling) and the indirect method, used by Itaipu Binacional, which considers the solid bottom discharge as 20% of the total, the granulometry is also gonna be done by sieving the bottom sediment of the Iguatemi River, affluent of the Paraná River by the right bank of Mato Grosso do Sul. More than 64% of all sediment that was collected of all samples were retained in the 50 mesh sieve (0,297), in highest flow discharge there were also bigger sediments, as for the solid discharge, there were differences of 1 to 2 times on the last samples and 5 times on the first one, caused by the use of a sampler without adaptation. About the solid discharge, it was demonstrated a proportion with the liquid discharge. Generally, the difference between the direct and indirect estimation method of solid discharge is small.