Number of polluted river-sites shows slight reduction: CPCB

The number of locations in Indian rivers unfit to bathe, saw an incremental dip to 807 in 2023 from 815 in 2022, according to a report by the Central Pollution Control Board (CPCB) made public on Monday. There was, however, a reduction in the number of river locations considered ‘most polluted’.

The agency monitors and compiles data in two-year stretches on the health – specifically measuring a parameter called biological oxygen demand (BOD) of India’s rivers. BOD is proxy for organic matter dissolved in water with a low number indicating a healthy river. A BOD greater than 3 milligrams/litre indicates rising pollution and is considered unfit for bathing.

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Two continuous locations, that exceed the criteria, in a single river is counted as a ‘polluted river stretch’ (PRS). In 2023, there were 296 PRS/locations found in 271 rivers. In 2022, there were 311 PRS/locations in 279 rivers.

Maharashtra (54) had the maximum number of PRS or locations followed by Kerala (31), Madhya Pradesh and Manipur with 18 each, and Karnataka (14). However, Tamil Nadu, Uttar Pradesh and Uttarakhand had the maximum number — five — of stretches or locations in ‘Priority 1’.

In the 2022 assessment, Gujarat and Uttar Pradesh had the maximum number of ‘Priority 1’ river stretches (6), Maharashtra had the maximum number of polluted river stretches i.e. 55, followed by Madhya Pradesh (19), Bihar (18), Kerala (18), Karnataka (17) and Uttar Pradesh (17).

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PRS with a BOD exceeding 30 mg/L are considered ‘Priority 1’, meaning, the most polluted and thus needing the most urgent remediation. There are five such categories with ‘Priority 2’ indicating a BOD of 20-30 mg/L and ‘Priority 5’ indicating 3-6 mg/L. The success of river-cleaning programmes are measured by the number of stretches moving from 1 to 2, 2 to 3 until those in 5 (requiring the least action).

In the latest assessment, the number of ‘Priority 1’ stretches reduced to 37 from 45 over the 2022 assessment, from 72 to 45 in ‘Priority 4’ and, 175 to 148 in ‘Priority 5’. There was increase in the number of ‘Priority 2’ and ‘Priority 3’ stretches — a sign that more river stretches were being remediated, according to the CPCB.

The CPCB network monitors water quality at 4,736 locations across the country including rivers, lakes, creeks, drains and canals.

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In 2018, when the CPCB published its report (after analysing stretches in 2016 and 2017), there were 45 stretches categorised in Priority 1, 16 in Priority 2, 43 in Priority 3, 72 in Priority 4 and 175 in Priority 5.

Following a report published in The Hindu in 2018, the National Green Tribunal (NGT) had passed orders that the CPCB and the Jal Shakti Ministry monitor river pollution and ensure that all acts of river pollution were dealt with. Every State had to ensure that at least one river stretch was “restored” to the extent that it was at least fit for bathing. States were also directed to implement ‘Action Plans’ detailing how they were addressing different stretches of their rivers.