Satellite derived estimation of Chlorophyll-a on Harmful Algal Blooms (HABs) in selected dams of Vhembe District, Limpopo Province

Abstract

Satellite remote sensing techniques have been proved to be capable of quantifying chlorophyll-a (Chl-a) levels by estimating algal concentrations in water bodies. Harmful algal blooms (HABs) pose a significant threat to many water bodies in South Africa. This study aimed at using a remote sensing solution to estimate chlorophyll concentrations in water bodies of Vhembe District Municipality using Landsat 8 OLI. This study seeks to provide quantitative water quality information for the Vhembe region’s water bodies from a time series of satellite remotely sensed data and in-situ laboratory data. The 30 meters spatial resolution multispectral Landsat 8 OLI for 2016, 2017 and 2018 were used to derive Chl-a estimate at three water bodies, namely, Nandoni, Albasini and Vondo reserviors. The Chl-a concentrations obtained from Landsat 8 (OLI) satellite were compared with the laboratory analysis using the Kappa coefficient statistical analysis. This study show that Landsat derived chl-a estimates have a high positive correlation of 80–90% accurate with field measurements. In all the reservoirs, it was detected that there is low content of HABs and thus the water bodies are in good condition since the chl-a concentrations were very low. In conclusion, it can be stated that Landsat 8 OLI sensor can be used to map and monitor inland water bodies dominated by algal blooms to a certain extent.