1.1 RIVERS BIO-MAPPING CONCEPT

The concept of water quality mapping had been initiated with the identification of beneficial uses of water in terms of primary water quality criteria. CPCB has prepared Water Quality Atlas of the Indian Rivers System on the basis of five major uses of river water such as:

a) Drinking water source without conventional treatment but after disinfection;

b) Outdoor bathing organized;

c) Drinking water source with conventional treatment followed by disinfection;

d) Propagation of wildlife, fisheries;

e) Irrigation, industrial cooling, controlled waste disposal.

The concept of bio-mapping originated alongwith use of biological system for classification and zoning of water bodies according to their level of ecological degradation.

Ø Bio-mapping is classification of biological water quality data of river basin in the form of a colour map of various biological classes of water bodies. Different colours such as Blue, Light Blue, Green, Orange and Red, on a river basin map indicate various grades of water quality in terms of clean, slight pollution, moderate pollution, high pollution and severe pollution in the water body respectively.

Ø Bio-mapping is a continuous bio-monitoring programme of river basin, which should be carried out every year to obtain information on changes in biological water quality maintaining an inventory of the biological life sustained by the river.

Ø Bio-mapping is carried out effectively for the rivers and tributaries of a river basin, where as bio-monitoring can be done for all surface water bodies and the water quality class can be depicted by colour comparison.

Ø Bio-mapping of water quality has become significantly important exercise for pollution control activities because:

a) It gives an immediate impression of the quality of a water body, subjected to multiple designated-best-uses.
b) It helps in the identification of water bodies, in need of improvement.
c) To know the extent of pollution control needed for restoration of water quality.
d) To collect the information on long-term cumulative effects of all adverse environmental factors.
e) To maintain and restore the ecological sustainability of the water body in terms of its wholesomeness.
f) Action plans can be prepared by simple colour comparison of the colour maps of water quality drawn for previous years.
g) It may also help in performing the formulation of national pollution control programme.

1.2 RIVERS BIO-MAPPING TECHNIQUES

· Benthic macro-invertebrates are the best suitable biological marker among the biotic communities in an aquatic ecosystem for bio-mapping.
· Locations on a river basin map are selected for biological sampling.
· Biological sampling is undertaken at about 0 to 5 cm depth of bottom substratum layer with the help of nets, shovels, dredges, artificial substratum etc.
· Taxonomic identification of benthic macro-invertebrates up to family level is undertaken at sampling locations itself.
· Collection of relevant environmental information according to field protocols.
· Biological water quality evaluation by - a) Saprobic score; b) Diversity score.
· Assigning the water quality class to each sampling location with respect to combinations of saprobic and diversity score of benthic macro-invertebrates collected from selected sampling locations.
· Biological water quality assessment with the help of Biological Water Quality Criteria (BWQC).
· Translating the biological water quality class of each location on river basin map to respective colours assigned in BWQC.
· Grouping the benthic macro-invertebrate families collected from various locations of river stretch with respect to Biological Water Quality Class and Indicator Colours.

1.3 BIOLOGICAL WATER QUALITY CRITERIA (BWQC)

This BWQC criteria is based on the range of saprobic values and diversity of benthic macro-invertebrate families with respect to water quality (Table 1). To indicate changes in water quality according to pollution levels, the taxonomic groups of benthic macro-invertebrate families with their saprobic score range from 0 to 10, in combination with the range of diversity score from 0 to 1 have been classified into five different classes. The abnormal combination of saprobic score and diversity score indicates sudden change in environmental conditions and poor substratum of water body.

Table 1: Biological Water Quality Criteria (BWQC)