Yamuna has failed to show any improvement in its pollution level in the past one year despite gradual reduction in pollution load contributed by major drains in Delhi, says an Environment Ministry report.
According to the Environment Ministry's Annual Report (2014-15), a Central Pollution Control Board (CPCB) study has found that discharge of sewage water into Yamuna has declined in the past one year though it still remains one of the top reasons behind the deterioration in the river's water quality.
Possible reasons for this decline are diversion of treated or untreated wastewater for irrigation and increased efficiency of waste water collection, transportation and treatment system, the report states.
The government has spent Rs 1,514.70 crore under Yamuna Action Plan I and II for creation of new sewage treatment capacity of 942.25 million litres per day (mld) in Delhi, Haryana and Uttar Pradesh.
However, the CPCB study conducted in the about 40-km stretch in Delhi said pollution level in the river has remained unchanged.
"This might be due to less availability of fresh water in the river, essential to maintain self-purification capacity of the river. Less availability of fresh water in the river may be due to reduction in the rain fall in the catchment area or increased rate of water abstraction from the river," it said.
CPCB regularly monitors water quality of Yamuna at four locations -- Palla, Wazirabad Barrage, Nizamuddin Bridge and Okhla at Kalindi Kunj -- in the about 40-km stretch in Delhi.
The water quality status of this stretch suggests that values of Dissolved Oxygen (DO) observed during first ten months of 2014 was well above the prescribed limit of 4.0 milligram/litre (mg/l) at Palla and was in the range from 6.4-11.0 mg/l. It depletes significantly after Wazirabad Barrage and remains critical in remaining part of the stretch.
At Okhla, Biochemical Oxygen Demand values were found well above the prescribed limit (9-79 mg/l). The report also says that the presence of 'free ammonia' is showing increasing trend as compared to observations of 2013.
"The reason of deterioration of Yamuna River water quality in Delhi stretch especially after Wazirabad barrage is due to unabated discharges of waste water predominantly from domestic sources into the river," the report says.
