Utilização do Acoustic Doppler Profiler (ADP) para a estimativa da Concentração de Sedimentos em Suspensão (CSS) e turbidez

Abstract

The equipment called ADCP / ADP (Acoustic Doppler Current Profiler / Acoustic Doppler Profiler) are being widely used in hydrometric for determining flow rates, due to faster handling and obtaining information from numerous cross sections analyzed in comparison to conventional methods. This current meter hydrostatic operation is similar to the search sonar and measuring the velocity of the stream of water on time interval and depth. Its operation is based on the principle of the Doppler effect, emitting sound waves in the water stream and a portion of these beams is reflected back to the source station and another part is absorbed by suspended sediments in the water and / or directed to points distinct source. Using this assumption, researchers are investigating if there is a possibility of relating information of sonorous intensity obtained by using ADP with SSC, thus enabling the determination of the solid discharge into waterways. To contribute to the research of the topic, this study sought to investigate this unknown in two distinct stages. The first step consisted of setting up an experimental apparatus consisting of a tank filled with water and a recirculation system. Different mixes of previously classified sands and soils were introduced into the reservoir, allowing for an artificially produced SSC. By using an ADP, concentrations were related to the different sediments while the intensity of the return signal was measured. The second stage investigation was conducted in the Vacacaí-Mirim River, which has natural flow conditions. It was sought to verify the use of ADP for turbidity, an alternative method for replacement of SSC. The general results of the laboratory analysis indicate that there is a relationship between the measure and the CSS echo measured by ADP, extracted from the average of the transducers. Only the results for Groups 1 and 2 showed low correlations and records echoes measured below the all samples collected. By applying the equations for the echos of adjustments resulting from measured samples of all groups, the linear fit showed 76% and 67% exponential fit of CSS calculated in the range of restrictive Factor 2, indicating the possibility of further assessment of sediment concentrations were obtained from eco measured by ADP. For field investigations, relating the echo with the turbidity, the results are promising, there was good correlation between the data with linear fit and 96% exponential 87% between tracks restrictive Factor 2, although few samples. In this step were identified limitations regarding the maximum value measured turbidity and this fact encourages further research on the subject.