Estimating the CDOM absorption coefficient in tropical inland waters using OLI/Landsat-8 images

Abstract

Coloured dissolved organic matter (CDOM) is the most abundant dissolved organic matter (DOM) in many natural waters and can affect the water quality, such as the light penetration and the thermal properties of water system. So the objective of this letter was to estimate the CDOM absorption coefficient at 440 nm, a CDOM (440), in Barra Bonita Reservoir (São Paulo State, Brazil) using operational land imager (OLI)/Landsat-8 images. For this two field campaigns were conducted in May and October 2014. During the field campaigns remote sensing reflectance (R rs) were measured using a TriOS hyperspectral radiometer. Water samples were collected and analysed to obtain the a CDOM (440). To predict the a CDOM (440) from R rs at two key wavelengths (650 and 480 nm) were regressed against laboratory-derived a CDOM (440) values. The validation using in situ data of a CDOM (440) algorithm indicated a goodness of fit, R 2 = 0.70, with a root mean square error (RMSE) of 10.65%. The developed algorithm was applied to the OLI/Lansat-8 images. Distribution maps were created with OLI/Landsat-8 images based on the adjusted algorithm.

In Situ and Satellite Observation of CDOM and Chlorophyll-a Dynamics in Small Water Surface Reservoirs in the Brazilian Semiarid Region

“…A study carried out in the hypertrophic Barra Bonita hydroelectric reservoir located in São Paulo (subtropical Brazilian region), which has a storage capacity of 2.600 hm³ measured aCDOM(440) equal to 1.6 m -1 in May 2014 (end of the wet season) and around 2.8 m -1 in October 2014 (end of the dry season) [60]. In the same study area, Alcântara et al [61] described aCDOM(440) values between 0.6 m -1 (in January 2014) and 1.7 m -1 (in September 2014) for this eutrophic system. Both works related the results to the seasonality with lower CDOM values for the wet season and higher concentration in the dry season.…”

In Situ and Satellite Observation of CDOM and Chlorophyll-a Dynamics in Small Water Surface Reservoirs in the Brazilian Semiarid Region

“…A study carried out in the hypertrophic Barra Bonita hydroelectric reservoir located in São Paulo (subtropical Brazilian region), which has a storage capacity of 2600 hm 3 , measured aCDOM(440) equal to 1.6 m −1 in May 2014 (end of the wet season) and around 2.8 m −1 in October 2014 (end of the dry season) [60]. In the same study area, Alcântara et al [61] described aCDOM(440) values between 0.6 m −1 (in January 2014) and 1.7 m −1 (in September 2014) for this eutrophic system. Both works related the results to the seasonality with lower CDOM values for the wet season and higher concentration in the dry season.…”

“…Similarly to our investigation, Alcântara et al [61] tested the potential of the red/blue-green ratio for predicting aCDOM(440) from Landsat-8 images. They also worked in the same hypertrophic reservoir studied by [60], and the best fit was yielded through the red-blue ratio band, derived by in situ hyperspectral remote sensing reflectance (Rrs), at 650 nm (L8 Band 4) and 480 nm (L8 Band 2), i.e., [Rrs(650)/Rrs(480)].…”

“…The presence of CDOM can be observed from the high absorbance of light in the shorter wavelength regions with the exponential reduction of values towards the longer wavelengths [11,61]. Because of the lowest phytoplankton concentration in PB and SN reservoirs throughout most of the observation period, we assign PB and SN to the spectral Group C, high color, oligotrophic, dystrophic system according to [10].…”

Phytoplankton community dynamic detection from the chlorophyll-specific absorption coefficient in productive inland waters

“…On the other hand, in October, the spectrum exhibited a higher absorption at 410 nm compared to 440 nm. For this month, Alcântara et al (2016a) reported that the Tietê River section before confluence had the highest dissolved organic matter concentrations and, consequently, a CDOM . Thus, the bio-optical status of this section may have led to a different phytoplankton deployment in relation to the rest of the reservoir .…”