Estimation of Chlorophyll-a Concentration and the Trophic State of the Barra Bonita Hydroelectric Reservoir Using OLI/Landsat-8 Images

Abstract

Reservoirs are artificial environments built by humans, and the impacts of these environments are not completely known. Retention time and high nutrient availability in the water increases the eutrophic level. Eutrophication is directly correlated to primary productivity by phytoplankton. These organisms have an important role in the environment. However, high concentrations of determined species can lead to public health problems. Species of cyanobacteria produce toxins that in determined concentrations can cause serious diseases in the liver and nervous system, which could lead to death. Phytoplankton has photoactive pigments that can be used to identify these toxins. Thus, remote sensing data is a viable alternative for mapping these pigments, and consequently, the trophic. Chlorophyll-a (Chl-a) is present in all phytoplankton species. Therefore, the aim of this work was to evaluate the performance of images of the sensor Operational Land Imager (OLI) onboard the Landsat-8 satellite in determining Chl-a concentrations and estimating the trophic level in a tropical reservoir. Empirical models were fitted using data from two field surveys conducted in May and October 2014 (Austral Autumn and Austral Spring, respectively). Models were applied in a temporal series of OLI images from May 2013 to October 2014. The estimated Chl-a concentration was used to classify the trophic level from a trophic state index that adopted the concentration of this pigment-like parameter. The models of Chl-a concentration showed reasonable results, but their performance was likely impaired by the atmospheric correction. Consequently, the trophic level classification also did not obtain better results.

Spatiotemporal Variation of Turbidity Based on Landsat 8 OLI in Cam Ranh Bay and Thuy Trieu Lagoon, Vietnam

“…Among them, FLAASH is one of the most widely used tools because of its higher accuracy and easier use compared to the others [14,20,[27][28][29][30].…”

“…The key parameters used in the FLAASH module of ENVI were: tropical for atmospheric model, tropospheric for the aerosol model because the study area is far from urban or industrial locations belonging to tropical area, and 2-band (K-T) for the aerosol retrieval; initial visibility was chosen as 40 km, depending on the image quality, and no water retrieval was conducted because no specific band was configured with the Landsat instruments. After carrying out the atmospheric correction, radiance values were converted into surface reflectance (ρ w ) [30] which was further converted to remote sensing reflectance (R rs ) by dividing pi (π):…”

Remote sensing of the chlorophyll-a based on OLI/Landsat-8 and MSI/Sentinel-2A (Barra Bonita reservoir, Brazil)

“…In turn, the MultiSpectral Instrument (MSI) onboard Sentinel-2A satellite was launched in June 2015 (ESA, http://www.esa.int/ ESA). Now with availability of both sensors data, several researches have been conducted in order to extract information for water color applications such as optical properties and OSCs (Watanabe et al 2015). In this context, the goal of this research was to evaluate the performance of OLI/Landsat-8 and MSI/Sentinel-2A sensors-based empirical algorithms in estimating Chl-a concentration in a tropical productive reservoir.…”

Drought can cause phytoplankton growth intensification in Barra Bonita reservoir

“…Due to eutrophication and high retention time there is an intense phytoplankton biomass growth (Calijuri et al 2002;Dellamano-Oliveira et al 2008;Watanabe et al 2015). According to Barbosa et al (1999), the Barra Bonita reservoir is classified as a polymictic ecosystem influenced by wind, fluctuations in rainfall, intrusion of water from tributaries, low retention time in austral summer and density currents caused by the two tributaries (Piracicaba and Tietê rivers), leading the horizontal and vertical mixing within the aquatic system.…”