Author(s): Carlo Gualtieri; Santiago Yepez; Mauricio Bermudez; Alain Laraque

Linked Author(s): Carlo Gualtieri, Alain Laraque

Keywords: Hydrodynamics; Sediment transport; Orinoco River; Field measurements; Remote sensing

Abstract: The Orinoco River has the third largest discharge in the world, with an annual mean flow of 37600 m3/s at the outlet to the Atlantic Ocean. The annual hydrological regime of the lower Orinoco at its main flow gauging station at Ciudad Bolivar in Venezuela is characterized by a unimodal regime where the rising waters begin in April, reaching its maximum streamflow in August. The sedimentological cycle in the hydrological station at Ciudad Bolivar is bimodal, marked by two TSS peaks respectively, before and after the maximum discharge peak. Since 2012 several field studies were carried out from the IMF/UCV and the IRD/GET (HYBAM Programme) to characterize hydrodynamics and sediment transport in different reaches of the Orinoco River. The studies were performed in low, medium, and high flow conditions. During this field campaign, Acoustic Doppler Velocity Profiling (ADCP) was used as well as water sampling for the measurement of TSS. The study was complemented by the analysis of remote sensing images, which demonstrated to be a time-efficient and accurate tool. This paper is focused on the analysis of the data about hydrodynamics and sediment transport in the reach, having an average width of 1 km, close to the city of Ciudad Bolivar, which is located approximately 350 km from the Orinoco mouth. The ADCP measurements gained a comprehensive characterization of the basic hydrodynamics parameters in that reach as well as their variation in different flow conditions during the hydrological year. During the field measurements, the flow discharge was in the range from 10000 to 65000 m³/s. Large velocities up to 3 m/s were observed, while water depth was in the range from 25 to 36 m from low to high flow conditions. Drag coefficients and bed shear stresses were also estimated. In addition to that, in this study we developed a parallel analysis of sediment transport (in the study reach) using time series of satellite images and in situ data acquired, including an evaluation of the relationship between the ADCP signal and the TSS concentration (at depth) to calculate the hydro-sedimentary flows. At the end, this study is the first comprehensive analysis of hydrodynamics and sediment transport in the Orinoco River using a combination of field and remote data.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022576

Year: 2022