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...oaded fromsmetals and sediments. Nutrients in coastal waters have caused a number of environmental problems, such as death of benthic fauna and demersal fish, the occurrence of nuisance algal blooms (=-=Paerl, 1988-=-), and the disappearance of seagrass and mangroves (Silberstein et al., 1986). Suspended sediment directly limits light penetration and reduces primary productivity. Therefore, it is very important to...

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...n practice is to collect in situ samples as sizeable as possible. A portion of them is used to construct the empirical model while the remainder is used as independent checkers to verify the results (=-=Gordon et al., 1983-=-; Khorram, 1985; Lindell et al., 1985; Gracia and Caselles, 1990; Gitelson et al., 1993; Gao and O’Leary, 1997a). The number of in situ samples that has been collected in the past is rather small, var...

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... wavelengths but increases it in green wavelengths. With an increase in chlorophyll concentration the position of peak reflectance shifts from about 680 to 715 nm while peak reflectance itself rises (=-=Gitelson, 1992-=-). Both the magnitude and the peak position of reflectance can be used as precise indicators and predictors of phytoplankton concentration.sIII Requirements of quantification Theoretically, it is impo...

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...on, remotely sensed data acquired from an aircraft or a satellite provide a synoptic view not attainable otherwise. This advantage has been widely exploited to monitor and map shallow coastal waters (=-=Bierwirth et al., 1993-=-). The repetitive viewing capability of remote sensing systems has been utilized to study the relationship between suspended sediment and chlorophyll concentrations and the distribution/intrusion patt...

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...May 16, 2016ppg.sagepub.comDownloaded fromsY Liu et al. 33 Australian coast can be estimated using existing analytical and modelling techniques, provided they can be characterized by in situ samples (=-=Jupp et al., 1994-=-). Some algal types and their concentrations are related to CASI data. The relationship can be exploited to detect and monitor algal blooms (Hick et al., 1998). A dense algal bloom at Lake Patzcuaro, ...

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...tance values on remotely sensed imagery can be simple linear, multiple linear or nonlinear, even though simple linear is the most common (Lopez-Garcia and Caselles, 1987; Lathrop and Lillesand, 1989; =-=Lathrop, 1992-=-; Aguirre-Gomez, 2000). Simple linear models are able to shed insightful light on water quality. Linear regression analysis is also effective and robust in inferring turbidity despite possible variati...

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...e data exhibited spatial structures related to water quality (Danson et al., 1991). Under ideal circumstances TM can be used to assess chlorophyll a and SDD with a limited accuracy for inland waters (=-=Dekker and Peters, 1993-=-).sSPOT data are available in three bands covering green to NIR wavelengths (a shortwave IR band was added to SPOT-4). The green band is least correlated with water quality parameters, whereas the red...

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...nd waters in estuaries (Choubey, 1997).sIn multiple linear regression analysis, a water quality parameter is regressed against the reflectance values in a few bands (Johnson et al., 1981; Lathrop and =-=Lillesand, 1986-=-; Shimoda et al., 1986; Rimmer et al., 1987). For instance, water quality parameters were modelled as multiple linear predictors of Landsat MSS bands 4, 5 and 6 in addition to sun elevation (Carpenter...

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...ality (Cairns et al., 1997).sNo definite conclusions have emerged from the above discussion regarding the strength, form or even the optimum wavelengths of remote sensing of water quality parameters (=-=Curran and Novo, 1988-=-). The lack of agreement is attributed to the spatial and temporal variability of sediment size, shape, mineralogy, variation in the range of concentration levels of in-water constituents and the pres...

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... primarily for terrestrial observations.sOf the six CZCS bands, four are designed to detect chlorophyll and yellow substance. CZCS blue and green bands are good at mapping chlorophyll concentrations (=-=Gordon et al., 1980-=-, 1983; Smith and Baker, 1982; Guan et al., 1985). Nevertheless, the absence of infrared bands from the CZCS sensor hampers effective atmospheric correction. This inability leads to inaccurate results...

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...ded sediment) is and whether other parameters, if present, interfere with its spectral reflectance. In case of co-existence, not all water constituents contribute to the recorded reflectance equally (=-=Bowers et al., 1998-=-). The infinite combinations of diverse water constituents create a wide variation in the spectral reflectance of shallow waters. Water-leaving radiant energy over the visible light portion of the spe...

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...ds, but low for chlorophyll a concentrations because of the broad MSS bandwidth. MSS-based predictions are very reliable for Secchi estimates and moderately reliable for chlorophyll a concentrations (=-=Lillesand et al., 1983-=-).sTM imagery has a finer spectral resolution than MSS. The improved resolution substantially increases the accuracy of quantifying SDD, chlorophyll a concentrations, and turbidity (Lathrop and Lilles...

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... portion of the spectrum (500–1100 nm). MSS data are able to generate reliable estimates of suspended sediment concentrations between 50 and 250 mg l–1, beyond which underestimation is rather common (=-=Ritchie and Cooper, 1988-=-). MSS red and NIR bands are more appropriate for predicting surface water quality characteristics (Harrington et al., 1992). Band 4 data are closely correlated with depth-integrated Secchi disk depth...

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...ary, 1997b). Turbidity causes light to be scattered and absorbed instead of transmitted. It is linearly correlated with suspended sediment concentration if water constituent particles are homogenous (=-=Forster et al., 1992-=-). Sediments of differing size but the same concentration reduce turbidity. Hence, it is problematic to estimate suspended sediments from turbidity or vice versa. Water turbidity can be correlated wit...

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...sed bands are TM1 (Lopez-Garcia and Caselles, 1987; Gracia and Casselles, 1990), TM2 (Lathrop and Lillesand, 1986). Besides, (TM1–TM3)/TM2 is a useful index for estimating chlorophyll concentrations (=-=Mayo et al., 1995-=-). As a matter of fact, ratioed wavelength bands and line height algorithms provide the best correlations to ground-truthed chlorophyll a (Dierberg and Carriker, 1994).sThe distribution of chlorophyll...

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...itoring requirements (McKim et al., 1984). Significant relationships established between chlorophyll a and TM data led to modelled chlorophyll results consistent with the available general knowledge (=-=Baban, 1993-=-). Maracci and Ooms (1988) merely mentioned that analytical results of chlorophyll determination were in good agreement with optical in situ data. Suspended matter concentrations in a plume mapped fro...

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...lysis has been introduced to model the transfer function between chlorophyll and sediment concentrations and satellite-received radiance with a much higher accuracy than multiple regression analysis (=-=Keiner and Yah, 1998-=-).sRegardless with which method or in what form they are constructed, the empirical and semi-empirical models are site-specific in most cases. For instance, the algorithms between reflectance and wate...

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...arn, 1995). The relationship is quite accurate for SDD<16 m. Highly significant models have been developed for SDD from a variety of data, including MSS (Garrison and Bryant, 1981; Verdin, 1985), TM (=-=Lavery et al., 1993-=-; Allee and Johnson, 1999) and even video data (Mausel et al., 1991). SDD is closely correlated with TM data, especially during high tide (Braga et al., 1993). The correlation achieved was as high as ...

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...rophyll a and pheaophytin was retrieved from remotely sensed data at a discrepancy of 23% from in situ measurements for concentration of 2 mg m–3 and at 10–12% for concentrations exceeding 12 mg m–3 (=-=Hoogenboom et al., 1998-=-). Interpretation techniques developed to process the spectra of upwelling radiation from water in the visible spectrum make it possible to retrieve chlorophyll a concentration with a standard error o...

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... phenomena detected via remote sensing are thus restricted to the surface of the water body. Fluorescence signal is reduced to 30% if phytoplankton is below 2 m instead of reaching the water surface (=-=Fischer and Kronfeld, 1990-=-).sThe spectral behaviour of water parameters varies with the type of constituent. Increases in suspended particulates lead to increases in overall brightness in the narrow band reflectance spectra (H...

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...Sicily were modelled rather adequately (Khorram et al., 1991). Highly significant empirical models were established for chlorophyll concentration and SDD from atmospherically corrected bands 1 and 3 (=-=Pattiaratchi et al., 1994-=-). On the negative side, airborne TM radiance could not be related directly to chlorophyll a concentration, even though the image data exhibited spatial structures related to water quality (Danson et ...

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...and, 1986; Shimoda et al., 1986; Rimmer et al., 1987). For instance, water quality parameters were modelled as multiple linear predictors of Landsat MSS bands 4, 5 and 6 in addition to sun elevation (=-=Carpenter and Carpenter, 1983-=-). Local site and situation conditions cansat PENNSYLVANIA STATE UNIV on May 16, 2016ppg.sagepub.comDownloaded froms28 Quantification of shallow water quality parameters also be accommodated using var...

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...all brightness in the narrow band reflectance spectra (Harrington and Repic, 1995). The correlation coefficient between suspended sediment and remotely sensed data peaks in the green/red wavelengths (=-=Novo et al., 1991-=-). Thus, the optimum wavelength for quantifying suspended sediment concentration is 550–650 nm (Novo et al., 1989). Chlorophyllsat PENNSYLVANIA STATE UNIV on May 16, 2016ppg.sagepub.comDownloaded from...

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...1991). Multivariate instead of bivariate regression analysis is the default option in developing water quality parameter models from multitemporal remotely sensed data (Carpenter and Carpenter, 1983; =-=Ritchie et al., 1987-=-). Polynomial regression analysis, together with spectral derivative, enables the identification of wavelengths that can be used to characterize pigment compositions of phytoplankton species in an est...

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...rom the CZCS sensor hampers effective atmospheric correction. This inability leads to inaccurate results in Case 2 waters that are commonly dominated by suspended sediments and biogenic particulates (=-=Doerffer et al., 1999-=-). At a spatial resolution of 825 m, CZCS imagery is more appropriately suited for oceanic waters (Smith and Baker, 1982) at the regional scale such as continental shelf (Tang et al., 1998) than at a ...

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...m water in the visible spectrum make it possible to retrieve chlorophyll a concentration with a standard error of less than 2.6 mg l–1, and dissolved organic matter concentration less than 0.5 C l–1 (=-=Gitelson and Kondratyev, 1991-=-). Gordon et al. (1985) concluded that under typical atmospheric conditions phytoplankton pigment concentration (the sum of the concentrations of chlorophyll a and pheophytin a) can be extracted from ...

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...ow level of concentration, but the relationship became saturated (e.g., asymptotic) at high concentrations (Bowers et al., 1998). Linearity was achieved only after natural logarithmic transformation (=-=Lathrop et al., 1991-=-). An exponential model proves to be more accurate than others in all cases (Harrington et al., 1992). Apart from empirical and semi-empirical models, there are several strategies to model water quali...

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...he incident radiation. Suspended solid concentrations have been commonly determined from MSS data (Ritchie et al., 1987; Harrington et al., 1992; Schiebe et al., 1992), TM (Lathrop, 1992), SPOT data (=-=Ouillon et al., 1997-=-), and even colour and colour IR photographs (Khorram, 1981; Gao and O’Leary, 1997b). Photographs are able to reveal subtlety in sediment distribution because of their fine detail, but are subject to ...

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... chlorophyll (Quibell, 1992). The upwelling spectral signatures for algae were determined by the reflectance of the particles themselves, and by the absorption by the water surrounding the particles (=-=Quibell, 1991-=-). Concentrations of algae in the photic zone in the very turbid waters off the easternsat PENNSYLVANIA STATE UNIV on May 16, 2016ppg.sagepub.comDownloaded fromsY Liu et al. 33 Australian coast can be...

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...absorbance at 380 nm and yellow substance fluorescence intensity. Predicted yellow substance is more sensitive to a change in detrital material than a change in living phytoplankton in turbid waters (=-=Ferrari et al., 1996-=-). Passive remote sensing is not suitable for investigating waters with a high concentration of yellow substance because extremely strong absorption by water leads to an ‘abnormal’ shape of the reflec...

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...etween suspended sediment and remotely sensed data peaks in the green/red wavelengths (Novo et al., 1991). Thus, the optimum wavelength for quantifying suspended sediment concentration is 550–650 nm (=-=Novo et al., 1989-=-). Chlorophyllsat PENNSYLVANIA STATE UNIV on May 16, 2016ppg.sagepub.comDownloaded fromsY Liu et al. 27 strongly absorbs radiation at about 450 and 670 nm. A higher chlorophyll concentration reduces r...

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...ionship is quite accurate for SDD<16 m. Highly significant models have been developed for SDD from a variety of data, including MSS (Garrison and Bryant, 1981; Verdin, 1985), TM (Lavery et al., 1993; =-=Allee and Johnson, 1999-=-) and even video data (Mausel et al., 1991). SDD is closely correlated with TM data, especially during high tide (Braga et al., 1993). The correlation achieved was as high as –0.83 and –0.91 for the r...

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...ality conditions (Lathrop and Lillesand, 1989). Nonlinearity has been observed between suspended sediment concentration, turbidity and sensor reflectance (Moore, 1980; Collins and Pattiaratchi, 1984; =-=Harrington et al., 1992-=-; Xia, 1993). This is true even for hyperspectral data (Althuis, 1998). The fit function between suspended sediment concentrations and corrected satellite data is linear between 0.5 and 10 mg l–1 (Fro...

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...985; Gracia and Caselles, 1990; Gitelson et al., 1993; Gao and O’Leary, 1997a). The number of in situ samples that has been collected in the past is rather small, varying around 21 (Sunar, 1992), 22 (=-=MacFarlane and Robinson, 1984-=-) and 31 (Ramsey et al., 1992). Although a total of 25 samples were collected by Forster et al. (1993), only nine were available for chlorophyll a, of which two were used for thesat PENNSYLVANIA STATE...

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...5 µg l–1 with some calibration in turbid water (Stumpf and Tyler, 1988). Reliable estimates and accurate maps of total chlorophyll concentrations have been derived from high resolution airborne data (=-=Millie et al., 1992-=-), and TM data (Lopez-Garcia and Caselles, 1987). Highly significant, multitemporal predictive algorithms, established from field data collected at the time of the satellite overpass, existed between ...

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...als of low concentrations is subject mostly to the absorption characteristics of water, while the absorption characteristics of highly concentrated suspended particles are the most important factors (=-=Moore, 1980-=-). The spectral property of a particular water constituent is especially variable, both temporally and spatially in shallow waters of high river discharge and anthropogenic input.sShort-wavelength rad...

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...ed insightful light on water quality. Linear regression analysis is also effective and robust in inferring turbidity despite possible variation in water constituents and impact of bottom reflectance (=-=Fraser, 1998-=-). Univariate, linear regression analyses of ratioed bands provide the closest correlation to ground-truthed chlorophyll a (Dierberg and Carriker, 1994). Regression technique has strong potential for ...

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...ple. Secondly, the constraint of ground truthing within 2–3 hours of image acquisition considerably restricts the availability of field observations (Khorram et al., 1989; Chacon-Torres et al., 1992; =-=Harding et al., 1992-=-). In order to overcome the limitations associated with a small sample size, a frequently adopted alternative is to use all the available samples in constructing the empirical model and to base the va...

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...nted in the next section, followed by conclusions. II Spectral characteristics of shallow waters Remote sensing of water quality parameters relies on the spectral properties of waterleaving radiance (=-=Hinton, 1991-=-; Stumpf, 1992). It refers to the light re-emerging from water after the incident solar radiation is selectively absorbed and backscattered by inwater constituents. The water-leaving radiance captured...

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...t is not financially viable to acquire a large sample. Secondly, the constraint of ground truthing within 2–3 hours of image acquisition considerably restricts the availability of field observations (=-=Khorram et al., 1989-=-; Chacon-Torres et al., 1992; Harding et al., 1992). In order to overcome the limitations associated with a small sample size, a frequently adopted alternative is to use all the available samples in c...

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...lved. The level of suspended sediment concentration that has been quantified varies from 1–30 mg l–1 with background concentrations around 1–3 mg l–1 (Jorgensen and Edelvang, 2000) to over 50 mg l–1 (=-=Ritchie and Schiebe, 1985-=-; Ritchie et al., 1987). The quantification at the lower level is made possible owing to the use of Compact Airborne Spectrographic Imager (CASI) data with a super high radiometric resolution. A much ...

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...suspended particles variance (Ramsey et al., 1992). Remotely sensed reflectance values agreed well with in situ particle densities with an average R2 of 0.81 for Landsat data and only 0.53 for AVHRR (=-=Carrick et al., 1994-=-).sThe numerical accuracy of quantification is not routinely reported in the literature. When it is mentioned, the accuracy is rather vague in some cases. For instance, the accuracy of water turbidity...

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...over the large range of water quality conditions (Lathrop and Lillesand, 1989). Nonlinearity has been observed between suspended sediment concentration, turbidity and sensor reflectance (Moore, 1980; =-=Collins and Pattiaratchi, 1984-=-; Harrington et al., 1992; Xia, 1993). This is true even for hyperspectral data (Althuis, 1998). The fit function between suspended sediment concentrations and corrected satellite data is linear betwe...

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...hlorophyll concentrations (Ruzafa et al., 1996). The relationship between estuarine mixing processes and bathymetry was revealed after bathymetric data were integrated with airborne TM data in a GIS (=-=Ferrier and Anderson, 1996-=-). Overlay of a contour map of bathymetry over a suspended sediment concentration map in a raster GIS shed light on the relationship between the Fox River Plume dispersion and bathymetry in Green Bay,...

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...is band allows the detection of surface changes in suspended matter concentration on the order of 0.5 mg dm–3 (Bradtke and Krezel, 1994), and distinction of concentration variations above 0.5 mg l–1 (=-=Froidefond et al., 1999-=-). AVHRR imagery enables interpretation of water quality parameters and opens up the way in monitoring inland waters (Prangsma and Roozekrans, 1989). The spatial scale to which AVHRR data has been app...

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...ecchi depth measurements (Dekker et al., 1996). Research on estuarine and continental shelf sediment transport dynamics and marine phytoplankton dynamics can benefit tremendously from remote sensing (=-=Johnson and Harriss, 1980-=-). Simultaneously acquired remote sensing data and surface water quality samples may prove useful for studying spatial and seasonal variations in phytoplankton biomass in estuaries and coastal waters ...

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... than others in all cases (Harrington et al., 1992). Apart from empirical and semi-empirical models, there are several strategies to model water quality parameters, including Monte Carlo simulations (=-=Kondratyev et al., 1998-=-), and hydrodynamic and water quality model simulations (Lyon et al., 1988). Through simulations a forecasting system was developed to predict water quality variables (Yang et al., 1999). The National...

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...een found by several authors, but are unique to each body of water (Fraser, 1998). In fact, remote sensing algorithms derived for the open ocean waters are seldom applicable to lakes and inland seas (=-=Kutser et al., 1998-=-). For this reason, mapping of the same water quality parameter in different regions at different times requires development of series of models (Catts et al., 1985; Rimmer et al., 1987; Hinton, 1991)...

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...in the literature. When it is mentioned, the accuracy is rather vague in some cases. For instance, the accuracy of water turbidity measurements was sufficient to meet certain monitoring requirements (=-=McKim et al., 1984-=-). Significant relationships established between chlorophyll a and TM data led to modelled chlorophyll results consistent with the available general knowledge (Baban, 1993). Maracci and Ooms (1988) me...

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...te sensing quantification of water quality parameters. The latter is indicative of inherent optical properties (scattering, absorption and fluorescence) of the water column and in-water constituents (=-=Morel, 1980-=-; Sturm, 1981), even though it is also affected by illumination conditions, water depth and bottom reflectance if the depth is shallow. It is the radiant energy that can be used to study water quality...

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...n et al., 1993; Gao and O’Leary, 1997a). The number of in situ samples that has been collected in the past is rather small, varying around 21 (Sunar, 1992), 22 (MacFarlane and Robinson, 1984) and 31 (=-=Ramsey et al., 1992-=-). Although a total of 25 samples were collected by Forster et al. (1993), only nine were available for chlorophyll a, of which two were used for thesat PENNSYLVANIA STATE UNIV on May 16, 2016ppg.sage...

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... size, a frequently adopted alternative is to use all the available samples in constructing the empirical model and to base the validation on its goodness-of-fit (Stumpf and Tyler, 1988; Sunar, 1992; =-=Baranowska, 1993-=-; Lavery et al., 1993; Pattiaratchi et al., 1994). Other strategies for validation include use of regression coefficient (R2), significance level of the regressed model, normality test of regressional...

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...990; Walker, 1996). Compared with in situ measurements and ecological water quality modelling, remote sensing provides valuable additional information for chlorophyll a and Secchi depth measurements (=-=Dekker et al., 1996-=-). Research on estuarine and continental shelf sediment transport dynamics and marine phytoplankton dynamics can benefit tremendously from remote sensing (Johnson and Harriss, 1980). Simultaneously ac...

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...racy indicator (Wass et al., 1997). Multiple correlation coefficients in excess of R = 0.9 resulted from regression analysis of site sampled turbidity and chlorophyll a parameters to Landsat-TM data (=-=Forster et al., 1993-=-). An R2 value of 0.9 between reflectance ratios and chlorophyll concentration was used for the same purpose (Olszewski et al., 1999). Similarly, Garrison and Bryant (1981) reported that regression an...

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...Spectrographic Imager (CASI) data with a super high radiometric resolution. A much wider concentration level of 0.1–66 mg l–1 was estimated from air-borne spectrometer data at a wavelength of 380 nm (=-=Gitelson et al., 1993-=-). Since sediments are usually suspended in shallow waters, their quantification is confined to lakes (Ritchie and Cooper, 1988; Harrington et al., 1992), reservoirs (Choubey, 1997), bays (Khorram, 19...

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...ssible. A portion of them is used to construct the empirical model while the remainder is used as independent checkers to verify the results (Gordon et al., 1983; Khorram, 1985; Lindell et al., 1985; =-=Gracia and Caselles, 1990-=-; Gitelson et al., 1993; Gao and O’Leary, 1997a). The number of in situ samples that has been collected in the past is rather small, varying around 21 (Sunar, 1992), 22 (MacFarlane and Robinson, 1984)...

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...x CZCS bands, four are designed to detect chlorophyll and yellow substance. CZCS blue and green bands are good at mapping chlorophyll concentrations (Gordon et al., 1980, 1983; Smith and Baker, 1982; =-=Guan et al., 1985-=-). Nevertheless, the absence of infrared bands from the CZCS sensor hampers effective atmospheric correction. This inability leads to inaccurate results in Case 2 waters that are commonly dominated by...

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...n monitoring water quality of inland waters in estuaries (Choubey, 1997).sIn multiple linear regression analysis, a water quality parameter is regressed against the reflectance values in a few bands (=-=Johnson et al., 1981-=-; Lathrop and Lillesand, 1986; Shimoda et al., 1986; Rimmer et al., 1987). For instance, water quality parameters were modelled as multiple linear predictors of Landsat MSS bands 4, 5 and 6 in additio...

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...016ppg.sagepub.comDownloaded froms32 Quantification of shallow water quality parameters 1998). Such relationships enable water turbidity along the Swedish coastline to be mapped from Landsat imagery (=-=Lindell et al., 1985-=-).s2 Chlorophyll concentration Phytoplankton pigments consist mainly of chlorophyll a, b and c, of which chlorophyll a is derivable by means of remote sensing. Sun-stimulated natural fluorescence of c...

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...aries (Choubey, 1997).sIn multiple linear regression analysis, a water quality parameter is regressed against the reflectance values in a few bands (Johnson et al., 1981; Lathrop and Lillesand, 1986; =-=Shimoda et al., 1986-=-; Rimmer et al., 1987). For instance, water quality parameters were modelled as multiple linear predictors of Landsat MSS bands 4, 5 and 6 in addition to sun elevation (Carpenter and Carpenter, 1983)....

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...between suspended sediment concentration, turbidity and sensor reflectance (Moore, 1980; Collins and Pattiaratchi, 1984; Harrington et al., 1992; Xia, 1993). This is true even for hyperspectral data (=-=Althuis, 1998-=-). The fit function between suspended sediment concentrations and corrected satellite data is linear between 0.5 and 10 mg l–1 (Froidefond et al., 1993). Similarly, a linear relationship was observed ...

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...ynomial regression analysis, together with spectral derivative, enables the identification of wavelengths that can be used to characterize pigment compositions of phytoplankton species in an estuary (=-=Bagheri et al., 1999-=-). The incorporation of more spectral information into the modelling improves the accuracy of the established model. Nevertheless, linear regression models are invalid for inland and shallow coastal w...

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...tration reduce turbidity. Hence, it is problematic to estimate suspended sediments from turbidity or vice versa. Water turbidity can be correlated with optical density of black and white photographs (=-=Bhargava, 1983-=-). The turbidity of the Tawa Reservoir, India is positively correlated with LISS-I bands 1, 2 and 3 data (Choubey, 1997). Turbidity can also be modelled from MSS data (Carpenter and Carpenter, 1983). ...

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...aving a secondary effect and yellow substance hardly any at all (Bowers et al., 1998). This band allows the detection of surface changes in suspended matter concentration on the order of 0.5 mg dm–3 (=-=Bradtke and Krezel, 1994-=-), and distinction of concentration variations above 0.5 mg l–1 (Froidefond et al., 1999). AVHRR imagery enables interpretation of water quality parameters and opens up the way in monitoring inland wa...

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...ven though logistics make this requirement problematic (Huang and Lulla, 1986). Nonsynchronization would cause the derived models to account for less variance in the dependent water quality variable (=-=Brown and Walsh, 1991-=-). Representative in situ samples should be collected over every possible type of water in a highly variable situation. Once acquired, in situ samples may be used to spectrally characterize water qual...

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... turbid waters. Although SPOT data are significantly correlated with turbidity and chlorophyll a, the correlation is so weak that they cannot be used as a practical tool for monitoring water quality (=-=Cairns et al., 1997-=-).sNo definite conclusions have emerged from the above discussion regarding the strength, form or even the optimum wavelengths of remote sensing of water quality parameters (Curran and Novo, 1988). Th...

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.... Simultaneously acquired remote sensing data and surface water quality samples may prove useful for studying spatial and seasonal variations in phytoplankton biomass in estuaries and coastal waters (=-=Catts et al., 1985-=-). The integration of remote sensing with in situ sample data leads to the creation of dynamic maps of suspended matters and facilitates oceanographic research (Molo et al., 1990). Airborne remote sen...

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...bidity and total suspended solids of low concentration, but more sensitive at a higher level of concentration. At most, suspended solids and chlorophyll a concentrations are derivable from SPOT data (=-=Chacon-Torres et al., 1992-=-). Owing to the coarse spectral resolution (finest 70 nm), caution must be exercised in delineating chlorophyll a levels in highly turbid waters. Although SPOT data are significantly correlated with t...

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...ll a (Dierberg and Carriker, 1994). Regression technique has strong potential for the future application of Indian Remote Sensing (IRS) data in monitoring water quality of inland waters in estuaries (=-=Choubey, 1997-=-).sIn multiple linear regression analysis, a water quality parameter is regressed against the reflectance values in a few bands (Johnson et al., 1981; Lathrop and Lillesand, 1986; Shimoda et al., 1986...

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...d temporal variability, the type of remotely sensed data used, the closeness of the regressed models and the quality of assessment data (Catts et al., 1985; Rimmer et al., 1987; Khorram et al., 1989; =-=Cipollini et al., 1993-=-). In situ data used in the assessment showed substantial variability and were poorly correlated with their image data even at short distances (Van Raaphorst et al., 1998).sVIII Conclusions This revie...

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... al., 1994). On the negative side, airborne TM radiance could not be related directly to chlorophyll a concentration, even though the image data exhibited spatial structures related to water quality (=-=Danson et al., 1991-=-). Under ideal circumstances TM can be used to assess chlorophyll a and SDD with a limited accuracy for inland waters (Dekker and Peters, 1993).sSPOT data are available in three bands covering green t...

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...riation in water constituents and impact of bottom reflectance (Fraser, 1998). Univariate, linear regression analyses of ratioed bands provide the closest correlation to ground-truthed chlorophyll a (=-=Dierberg and Carriker, 1994-=-). Regression technique has strong potential for the future application of Indian Remote Sensing (IRS) data in monitoring water quality of inland waters in estuaries (Choubey, 1997).sIn multiple linea...

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...ike pigment and total suspended sediment concentrations (Ferrari and Tassan, 1992). The absorption has been measured by a combination of beam transmission and induced fluorescence to a high accuracy (=-=Ferrari and Tassan, 1990-=-). Kowalczuk (1997) calculated the yellow substance absorption coefficient at 400 nm and yellow substance absorption spectrum slope coefficient. Sugihara and Kishino (1988) developed an algorithm for ...

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...ed and NIR bands are more appropriate for predicting surface water quality characteristics (Harrington et al., 1992). Band 4 data are closely correlated with depth-integrated Secchi disk depth (SDD) (=-=Garrison and Bryant, 1981-=-). The coefficients of empirical models are high for turbidity, relatively high for suspended solids, but low for chlorophyll a concentrations because of the broad MSS bandwidth. MSS-based predictions...

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...0).sThe spectral behaviour of water parameters varies with the type of constituent. Increases in suspended particulates lead to increases in overall brightness in the narrow band reflectance spectra (=-=Harrington and Repic, 1995-=-). The correlation coefficient between suspended sediment and remotely sensed data peaks in the green/red wavelengths (Novo et al., 1991). Thus, the optimum wavelength for quantifying suspended sedime...

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... can be characterized by in situ samples (Jupp et al., 1994). Some algal types and their concentrations are related to CASI data. The relationship can be exploited to detect and monitor algal blooms (=-=Hick et al., 1998-=-). A dense algal bloom at Lake Patzcuaro, Mexico was identified from SPOT images (Chacon-Torres et al., 1992). A thematic map of algae was generated from classification of TM data according to depth a...

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... collection with the recording of remotely sensed data effectively ensures that the temporal dynamics of water quality are taken into account, even though logistics make this requirement problematic (=-=Huang and Lulla, 1986-=-). Nonsynchronization would cause the derived models to account for less variance in the dependent water quality variable (Brown and Walsh, 1991). Representative in situ samples should be collected ov...

Citation Context

...relationship between water quality parameters and their reflectance values on remotely sensed imagery can be simple linear, multiple linear or nonlinear, even though simple linear is the most common (=-=Lopez-Garcia and Caselles, 1987-=-; Lathrop and Lillesand, 1989; Lathrop, 1992; Aguirre-Gomez, 2000). Simple linear models are able to shed insightful light on water quality. Linear regression analysis is also effective and robust in ...

Citation Context

...mi-empirical models, there are several strategies to model water quality parameters, including Monte Carlo simulations (Kondratyev et al., 1998), and hydrodynamic and water quality model simulations (=-=Lyon et al., 1988-=-). Through simulations a forecasting system was developed to predict water quality variables (Yang et al., 1999). The National Aeronautical and Space Administration (NASA) standard curve and the spect...

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... significant models have been developed for SDD from a variety of data, including MSS (Garrison and Bryant, 1981; Verdin, 1985), TM (Lavery et al., 1993; Allee and Johnson, 1999) and even video data (=-=Mausel et al., 1991-=-). SDD is closely correlated with TM data, especially during high tide (Braga et al., 1993). The correlation achieved was as high as –0.83 and –0.91 for the red band (644–656 nm), and 0.93 and 0.84 fo...

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... is also related to reflectance just below the surface in atmospherically corrected MSS green band, incorporating the ratio of backscattering to total scattering coefficients for suspended particles (=-=Mulhearn, 1995-=-). The relationship is quite accurate for SDD<16 m. Highly significant models have been developed for SDD from a variety of data, including MSS (Garrison and Bryant, 1981; Verdin, 1985), TM (Lavery et...

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...ze is kept the same as that of image pixels. A grid DEM has to be co-registered with the remote sensing image layers or referenced to a common coordinate system before it can be integrated with them (=-=Nichol and Gupta, 1990-=-). The incorporation of bathymetric data into water quality studies has facilitated mapping of coastal waters (Nichol and Gupta, 1990; Ruzafa et al., 1996), understanding of transportation of water co...

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...te sampled turbidity and chlorophyll a parameters to Landsat-TM data (Forster et al., 1993). An R2 value of 0.9 between reflectance ratios and chlorophyll concentration was used for the same purpose (=-=Olszewski et al., 1999-=-). Similarly, Garrison and Bryant (1981) reported that regression analyses revealed a good correlation between Secchi disk transparencies and Landsat band 4 data (R2 –0.85). Ground-truthed uncorrected...

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...n of dynamic maps of suspended matters and facilitates oceanographic research (Molo et al., 1990). Airborne remote sensing provides a useful means of mapping surface water quality in coastal regions (=-=Rimmer et al., 1987-=-). Satellite remote sensing can serve as a fast and relatively cost-effective tool for early and expeditious assessment of the spatial and temporal variability of lake water quality conditions (Ziliol...