Betsiboka, one of the largest rivers in Madagascar, flows into the Mozambique Channel at Mahajanga. It is also the river with the highest sediment load from ferralitic soils and known worldwide for its red color waters. The suspended matter load has progressively increased, to the point of almost filling the upstream part of the estuary and modifying the geomorphology of the entire downstream part, with the appearance of numerous islets. The objective of this study is to estimate the suspended matter load that the river drains using Sentinel2 satellite images.
85 measurements of suspended solids concentrations were made in synchronisation with images taken by the Sentinel2A and Sentinel2B satellites over the study area. An artificial neural network model was applied to the datasets of field measurements and Sentinel2 level 2A image pixels.
A Root Mean Square Error (RMSE) of 22 mg/L was obtained between the model predictions and the field measurements.
Betsiboka delta, Madagascar @ Aster, Nasa
This study shows the suitability of Sentinel2 images for monitoring water quality, particularly in the case of the Betsiboka River, which is heavily loaded with sediment. This method significantly improves the estimation of the quantities of sediments discharged into the different ecosystems that the river waters cross, the Bombetoka bay populated with mangroves, the delta and the sea.