A new methodology for presenting hydrodynamics data from a large river confluence

Confluences are very complex fluvial networks where the combination of matter (water and sediment) and energy (flow strength) from two different channels take place.The confluence of Rio Negro, with is black waters, and the Rio Solimões, with its suspended white sediments, is one of the biggest confluences on the earth and attracts thousands of tourists every year near by the city of Manaus, Amazonas – Brazil. This paper presents the application of a new method to analyze the ADCP data which is using an in-house FORTRAN code in combination with the Tecplot and Surfer Softwares. The method was applied to ADCP transects collected on this confluence within the EU-funded Clim-Amazon Projectin two different periods of the hydrological cycle: low flow conditions on 30 and 31 October 2014, during the FS−CNS1 campaign, and relatively high flow conditions on 29 and 30 April 2015, during the FS−CNS2 campaign, both of them included 23 transects. These data were first extracted with WinRiver II software to produce ASCII files. The ASCII files were first processed using the code to derive input files containing the three velocity components, the average backscatter as well as the secondary currents from the Rozovskii method. These data were plotted in Tecplot to gain cross-sectional profiles. Furthermore, as past investigations were limited to the analysis of the depth-averaged quantities, the FORTRAN code was used even to extract the values of the velocity components as well as the backscatter along three layers in the channel: near the bed, at mid-depth and near the water surface. The data were then used to prepare Surfer maps, in a plane contour map format, of these quantities. The analysis of the data along these three layers can provide further findings into the complex three-dimensional structure of the flow at the Negro/Solimões confluence.