5. CONCLUSIONS AND DISCUSSION 
The relationship between R(O-) and a and b h was determined to be 
* ( 0 -) 
- b > 
l a+b. 
r l w b 
(9) 
for inland waters as was already determined for coastal zone colour remote sensing models. Values of b b were best 
estimated as a fraction of scattering over 40° to 180°; the value for the fraction used in this study was 0.25. 
The r, was found to be much more variable for inland waters than for coastal and ocean waters. The coefficient 
r, varied with changing optical water type and illumination conditions; values for r, derived from the data ranged from 
0.12 to 0.56, with an average of 0.29. At the moment it is not possible to predict a value for r, which is applicable to 
a wide range of water bodies. A spectral dependence of r, was most markedly evident in the samples from the shallow 
eutrophic lakes. Therefore, information extraction from reflectance spectra requires the use of algorithms which are 
preferably independent of r, values. 
For the purpose of information extraction from reflectance spectra it is therefore recommended that algorithms 
which are independent of r, values are used. This requirement suggests the use of remote sensing algorithms that 
combine information from more than one spectral band in such a manner that r, values are normalised. Alternatively, 
algorithms which require information about the spectral behaviour of backscattermg and absorption can be used. 
Available data on volume scattering functions for different water types are scarce, especially for inland waters. 
In situ and laboratory optical measurements enabling the estimation of R(O-) and a and b remain necessary until approp 
riate volume scattering functions for inland waters are available. For the further development of an analytical method 
for inland water measurements of spectral volume scattering functions for the various fractions of freshwater related 
suspended matter (detritus, inorganic matter and phytoplankton) are required. 
Acknowledgements 
The Spectron SE-590 was provided by the University of Nottingham and calibrated by the equipment pool of the 
National Environmental Research Council, UK. A grant from NERC made it possible for Dr. T.J. Malthus to perform 
and analyze the measurements. J. Krijgsman and H. Hakvoort at the Faculty of Civil Engineering of the Technical 
University of Delft (NL) performed the spectrophotometric measurements. This work was funded by the National 
Remote Sensing Programme of The Netherlands via the Dutch Remote Sensing Board (BCRS) and by the Institute for 
Inland Water Management and Wastewater Treatment (NL). 
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