Spectral Analysis of Water Reflectance for Hyperspectral Remote Sensing of Water Quailty in Estuarine Water

Abstract

Hyperspectral remote sensing offers an effective approach for frequent, synoptic water quality measurements over a large spatial extent. However, the optical complexity of case 2 water makes the water quality monitoring by remote sensing in estuarine water a challenge. The prime objective of this study was to develop algorithms for hyperspectral remote sensing of water quality based on in situ spectral measurement of water reflectance. In this study, water reflectance spectra R(λ) were acquired by a pair of Ocean Optic 2000 spectroradiometers during the summers from 2008 to 2011 at Patuxent River, a tributary of Chesapeake Bay, USA. Simultaneously, concentrations of chlorophyll a and total suspended solids (TSS), as well as absorption of colored dissolved organic matter (CDOM) were measured. Empirical models that based on spectral features of water reflectance generally showed good correlations with water quality parameters. The retrieval model that using spectral bands at red/NIR showed a high correlation with chlorophyll a concentration (R 2 = 0.81). The ratio of green to blue spectral bands is the best predictor for TSS (R 2 = 0.75), and CDOM absorption is best correlated with spectral features at blue and NIR regions (R 2 = 0.85). These empirical models were further applied to the ASIA Eagle hyperspectral aerial imagery to demonstrate the feasibility of hyperspectral remote sensing of water quality in the optical complex estuarine waters.

The new Landsat 8 potential for remote sensing of colored dissolved organic matter (CDOM)

“…The consistent temporal coverage and broad spatial extent of satellite data provide a cost effective solution for frequent, synoptic water quality measurements. Numerous empirical, semi-analytical, and analytical models have been developed to estimate a range of parameters including chlorophyll a concentrations, total suspended solids (TSS), colored dissolved organic matter (CDOM), salinity, and temperature (Fan, 2014;Senay et al, 2002). Remotely sensed water quality measurements typically utilize empirical relationships between the spectral features of water reflectance and discrete in situ water samples, quantifying the water quality parameter(s) of interest (Fan, 2014).…”

Monitoring of Calcite Precipitation in Hardwater Lakes with Multi-Spectral Remote Sensing Archives

“…Yellow substances ("Gelbstoff") in the water absorb in ultraviolet and blue [2,10,11], however, as colored dissolved organic matter (CDOM) was not measured in situ, we cannot estimate its influence on our lake spectra.…”

“…The reference reflectance spectrum without calcite precipitation on 15 October 1999 has low reflectance values with a maximum blue band. Even though the reflectance spectra of calcite precipitation show higher NIR and SWIR reflectance, an analysis above 800 nm is not recommended as the absorption of clear water superimposes the effect of water components [1,2,11,25]. Figure 11 illustrates the variation of lake reflectance spectra with and without calcite precipitation.…”

“…They are also described as "whiting", "milky water phenomenon" or "seasonal clouding" [1][2][3]. The complex process of calcite precipitation has been intensively studied [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Application of HySpex hyperspectral images for verification of a two-dimensional hydrodynamic model

“…Water quality can be related to coloured dissolved organic matter (CDOM) originating from phytoplankton and surface runoff. An increase of content is identifiable in the blue range (Fan, 2014) and in the 571-670 nm range (Menken, Brezonik, & Bauer, 2005). The quotient of 430 nm and 620 nm bands (Dekker, 1993) was also used.…”