Bio-Mapping of Rivers, March 1999

BIOLOGICAL WATER QUALITY CRITERIA (BWQC)

To assess the actual health of water bodies, CPCB has derived a Biological Water Quality Criteria (BWQC) for water quality evaluation. This system is based on the range of saprobic values and diversity of the benthic macro-invertebrate families with respect to water quality. The system has been developed after extensive field trials and calibration on the saprobity and diversity information of different taxonomic groups of benthic animals collected from artificial substratum and natural substratum of various water bodies. To indicate changes in water quality to different grades of pollution level, the entire taxonomic groups, with their range of saprobic score from 1 to 10, in combination with the range of diversity score from 0 to 1 has been classified into five different classes of water quality (Table 1.b). The abnormal combination of saprobic score and diversity score indicates sudden change in environmental conditions.

Table 1.b : Biological Water Quality Criteria (BWQC)

 

S. No

 

Taxonomic groups

Range of saprobic score (BMWP)

Range of diversity

score

Water quality

characteristic

Water quality class

Indicator colour

1.

Ephemeroptera, Plecoptera, Trichoptera, Hemiptera, Diptera

7 and more

0.2 - 1

Clean

A

Blue

2.

Ephemeroptera, Plecoptera, Trichoptera, Hemiptera, Odonata, Diptera

6 - 7

0.5 - 1

Slight pollution

B

Light blue

3.

Ephemeroptera, Plecoptera, Trichoptera, Hemiptera, Odonata, Crustacea, Mollusca, Polychaeta, Hemiptera, Coleoptera, Diptera, Hirudinea, Oligochaeta

3 - 6

0.3 - 0.9

Moderate pollution

C

Green

4.

Mollusca, Hemiptera, Coleoptera, Diptera, Oligochaeta

2 - 5

0.4 & less

Heavy pollution

D

Orange

5.

Diptera, Oligochaeta

No animals

0 - 2

0 - 0.2

Severe Pollution

E

Red

Application of Biological Water Quality Criteria (BWQC)

Bio-assessment of raw water at drinking water sources (clean water bodies)

Under this study, three water bodies were selected for Bio-assessment, which are the main raw water sources for drinking water supply in Delhi namely; Western Yamuna Canal (WJC), River Yamuna and Gang Canal. Water quality of Gang Canal also represents the bathing water quality of River Ganga at Haridwar in U.P.

The Western Yamuna Canal originates from Tajewalla head works in Haryana state and terminates in River Yamuna in Delhi state through Najafgarh Drain. There are two major sources of pollution of Western Yamuna Canal i.e. the domestic and industrial waste water of Yamuna Nagar and Panipat in Haryana state.

Bio-assessment of water quality for irrigation, industrial cooling and controlled waste disposal (Polluted water bodies)

Under this study River Yamuna and Agra Canal in Delhi stretch was selected for biological water quality assessment.

The polluted stretch of River Yamuna lies within city limits of Delhi downstream of Wazirabad barrage. After traversing about 22 km, the river leaves Delhi at Okhla. There are 16 major drains, which discharge treated and untreated waste water/sewage of Delhi and Haryana and from Uttar Pradesh through Hindon Canal into Yamuna between Wazirabad and Okhla. As a result, the river water quality between Wazirabad and Okhla lies in `E' class of Designated-best-use criteria (Table 2). The Agra canal originates from Okhla barrage down stream of Nizamuddin bridge. Agra canal is an irrigation canal, and also receives the thermal discharges of Badarpur Thermal Power Plant. The Bio-assessment of water quality indicate severe pollution in canal water.

Table 2 Physico-chemical and biological water quality of polluted stretch of river Yamuna and Agra canal

 

S. No.

 

Location

Water quality class

Water quality (Biological)

Physico-chemical (PWQC)

Biological (BWQC)

1.

Okhla barrage (River Yamuna)

E

E

Severe Pollution

2.

Inlet of BTPP at Agra Canal

E

E

Severe Pollution

3.

Mixing of BTPP outlet at Agra Canal

E

E

Severe Pollution

BTPP = Badarpur Thermal Power Plant
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