First Experiences in Mapping Lake Water Quality Parameters with Sentinel-2 MSI Imagery

Abstract

Abstract:The importance of lakes and reservoirs leads to the high need for monitoring lake water quality both at local and global scales. The aim of the study was to test suitability of Sentinel-2 Multispectral Imager's (MSI) data for mapping different lake water quality parameters. In situ data of chlorophyll a (Chl a), water color, colored dissolved organic matter (CDOM) and dissolved organic carbon (DOC) from nine small and two large lakes were compared with band ratio algorithms derived from Sentinel-2 Level-1C and atmospherically corrected (Sen2cor) Level-2A images. The height of the 705 nm peak was used for estimating Chl a. The suitability of the commonly used green to red band ratio was tested for estimating the CDOM, DOC and water color. Concurrent reflectance measurements were not available. Therefore, we were not able to validate the performance of Sen2cor atmospheric correction available in the Sentinel-2 Toolbox. The shape and magnitude of water reflectance were consistent with our field measurements from previous years. However, the atmospheric correction reduced the correlation between the band ratio algorithms and water quality parameters indicating the need in better atmospheric correction. We were able to show that there is good correlation between band ratio algorithms calculated from Sentinel-2 MSI data and lake water parameters like Chl a (R 2 = 0.83), CDOM (R 2 = 0.72) and DOC (R 2 = 0.92) concentrations as well as water color (R 2 = 0.52). The in situ dataset was limited in number, but covered a reasonably wide range of optical water properties. These preliminary results allow us to assume that Sentinel-2 will be a valuable tool for lake monitoring and research, especially taking into account that the data will be available routinely for many years, the imagery will be frequent, and free of charge.

Shellfish Aquaculture from Space: Potential of Sentinel2 to Monitor Tide-Driven Changes in Turbidity, Chlorophyll Concentration and Oyster Physiological Response at the Scale of an Oyster Farm

“…Other algorithms could have been used. Besides the Gons et al (2005) method, various approaches were previously developed for turbid and/or eutrophic coastal and inland waters, including the 2-, and 3-band models (Dall'Olmo et al, 2005;Gitelson et al, 2008;Le et al, 2013), the fluorescence line height (FLH, Gower et al, 1999), the maximum chlorophyll index (MCI, Gower et al, 2005), and the 705 nm peak height (Toming et al, 2016). These algorithms are all based on a NIR/red edge either associated with chl a absorption at 675 nm or with sun-induced chl a fluorescence.…”

“…Chlorophyll a Algorithm Several algorithms are available for Sentinel2/MSI (Beck et al, 2016;Toming et al, 2016) to retrieve chl a concentration from ρ w (λ) in coastal waters. For our study site, an intercomparison exercise based on in situ measurements demonstrates that the chlorophyll-retrieval algorithm of Gons et al (2005) provided the most satisfactory results (see Supplementary Information for more details).…”

Assessment of Atmospheric Correction Methods for Sentinel-2 MSI Images Applied to Amazon Floodplain Lakes

“…which affects the atmospheric correction accuracy of Sen2Cor algorithm. Toming et al [12] found the shape similarity of MSI-corrected dataset using the Sen2Cor algorithm compared with a historical dataset (2011)(2012)(2013), although the MSI reflectance spectra were overestimated by the algorithm. In the Amazon context, the presence of forest surfaces benefits AOD retrievals by the Sen2Cor algorithm, however, this surface neighbour also implies in severe adjacency contamination on the water spectrum measured by orbital sensors.…”

Mapping phytoplankton blooms in deep subalpine lakes from Sentinel-2A and Landsat-8

“…1). S2A, launched on 23 June 2015, has been already used for the assessment of water constituents, for example, in the oligotrophic waters of Starnberg Lake and in the humic lakes (Toming et al, 2016). Moreover, the MSI bands close to the red-edge are promising for resolving productive turbid waters.…”