New Delhi, Jul 30 (IANS): The number of polluted river stretches across India have increased from 302 to 351 from 2015 to 2018, the Lok Sabha was informed when asked about the status of rivers across India.

Based on monitoring results in terms of biochemical oxygen demand (BOD), an indicator of organic pollution, the polluted river stretches are identified by the CPCB from time to time.

Considering this data between 2009 to 2012, "the report published in 2015 said there are 302 polluted river stretches across India while the same number had risen to 351 in 2018 as per the report based on monitoring data between 2016-2017," Minister of State for Jal Shakti & Food Processing Industries, Prahlad Singh Patel said in a written reply on Thursday.

Rivers in the country are polluted due to discharge of untreated and partially treated sewage from cities/towns and industrial effluents in their respective catchments, problems in operation and maintenance of sewage/effluent treatment plants, lack of dilution and other non-point sources of pollution. Rapid urbanisation and industrialisation have compounded the problem, the minister said.

The Minister also said, while reports by some experts have expressed concern about the reduction in water flow in rivers, the annual average flow data maintained by the Central Water Commission (CWC) for the last 20 years for major/important rivers in the country "does not indicate any significant decline in water availability."

However, as per the CWC, the per capita annual water availability in the country has progressively reduced due to increase in population, urbanisation, improved lifestyle of people, etc., the release said.

The 351 polluted river stretches have been categorized into 5 Priority Classes, based on BoD levels in mg/l: 45 stretches exceeding 30 mg/l, 16 stretches between 20-30 mg/l, 43 stretches between 10-20 mg/l, 72 stretches between 6-10 mg/l and as many as 175 stretches have BoD level between 3-6 mg/l, the release said.

The National River Conservation Plan (NRCP) has so far covered polluted stretches on 34 rivers in 77 towns spread over 16 states in the country with the sanctioned cost of projects as Rs 5,965.90 crore, and sewage treatment capacity of 2522.03 MLD created. Under the Namami Gange programme, a total of 346 projects, including 158 projects for sewage treatment of 4948 MLD and a sewer network of 5,213 kms have been sanctioned at a cost of Rs 30,235 crore, the government said.