Study on the Applicability of Landsat-8 Images as a Tool for Monitoring the Trophic State of Lake Guiers (Senegal)

In this study, an algorithm to transform LANDSAT 8 images of Lake Guiers into chlorophyll-a concentration maps was developed.The objective was to see the feasibility of this method as a mapping tool for monitoring the trophic state of the Lake.The available data are 15 in-situ measurements of the CHL-a content of Lake Guiers' water using a Micro FLU device and images of the lake acquired in 2013 and 2016 by the LANSAT 8 OLI sensor.A series of correlation tests (simple linear functions, multi-variables, or containing twoorder terms) were performed between the spectral sensor signal of June 19, 2016 LANSAT 8 image ("corrected" and converted into reflectance) and the CHL-a content of Lake waters measured on the same day of the satellite record.This was, to find the best regression equation that can be inferred to develop an algorithm to transform LANDSAT 8 image into CHL-a concentration maps.The best equation obtained by correlating the ground truths and the reflectance ratios of the visible and near infrared bands (B2, B3, B4 and B5), is as follows: