1.3 The reflectance of natural radiation falling on the surface 
of the water body is a characteristic of the quality of the 
water. This reflectance is contributed by (1) the surface of the 
water (2) the volume of the water (3) the bottom reflectance. The 
component contributed by the bottom surface of the water body 
has to be considered only in case of shallow waters. For waters 
of certain depth and beyond (i.e. the depth of Extinction) the 
bottom reflectance component is not significant. Hence, in such 
cases, reflectance is only due to the surface and the volume. The 
surface of the water body acts like a mirror, causing specular 
reflectance. The volume reflectance is caused by the scattering 
of light by the colloidal particles suspended in the water. 
1.4 The purpose ofthis investigation is to: 
a) Study the relationship between turbidity and spectral 
response of water bodies 
and 
b) To determine the influence of the bottom reflectance on 
the spectral response of water i.e. the depth upto which 
the bottom affects the spectral reflectance or the depth 
of Extinction. 
These studies will help in the interpretation of water bodies 
and thus increase the capacity to detect and monitor effectively 
and qualitatively the quality of water resources. 
2. Methodology 
2.1 The following water bodies have been selected for collection 
of data: 
I. Budunur: Situated about six kilometers from Mandya on 
Bangalore-Mysore highway. The particular water body consists 
of a series of fish tanks, the total area of which is about 
10 sq.m. The depth is about one and one half meters. These 
tanks are made of cement concrete. 
II. Chick Mandya: A small town adjoining Mandya. The water body 
is drainage water from Mandya tank. The water drops from 
about five meters and then flows. There are two bridges 
across. The data has been collected from these bridges which 
are of about 6.25 meters height above the water surface. The 
depth of water is about 2 1/2 meters at the centre and about 
1 1/2 meters near the banks. 
III.Hebbahalla: A drainage water flowing near Mandya town. This 
is an interesting site as wastes from sugar factory and the 
acetate factory are let into the stream at different locations. 
The mixing of both effluents can be distinctly observed. Sugar 
factory effluent looks dark brown and the Acetate factory 
looks whitish blue. 
IV. Kilara: Situated about 10 Kilometers from Mandya, this spot 
is a small pond of area about 15 sq.m. The depth is about 
2 meters. Water is clear. 
V. Echegera: Situated about 15 Kilometers east of Mandya, it is 
a pond of about 20 sq.m. area. Depth is about 1 1/2 meters. 
Water is dirty brown in colour.