As Delhi reeled under its fourth straight day of heatwave circumstances, Sanjay Lake in East Delhi’s Trilokpuri on Thursday became a fish graveyard – lots of of fish floated belly-up in shallow inexperienced swimming pools, geese waded by black slush and enormous stretches of the lake mattress lay cracked dry.
The deaths got here amid quickly receding water ranges on the lake, with officers attributing the state of affairs partly to a crucial pipeline supplying handled water from Kondli sewage remedy plant (STP) to the lake growing leakages and remaining under restore. Officers additionally mentioned the extended heatwave could have lowered oxygen ranges in already stagnant water. “The continued heatwave has solely worsened the disaster,” a authorities official mentioned.
The carcasses included small Gambusia or mosquitofish, together with bigger tilapia- or carp-like freshwater species.
In a written response to The Indian Specific, the Delhi Growth Authority (DDA) mentioned the factitious lake spreads throughout practically 187 acres, together with a 52.53-acre lake space maintained by it. The lake can be a notified protected forest under the Delhi Forest division.
It added that main restoration and infrastructure works, together with toe partitions and slope safety works meant to strengthen the lake’s embankments and stop erosion of its banks had been accomplished, however the duty for supplying handled water to keep up the extent on the lake is on the Delhi Jal Board (DJB). “The DDA has been constantly pursuing the matter with them,” it mentioned in the response.
A senior DJB official, talking on situation of anonymity, mentioned, “Handled effluent from Kondli STP is equipped to Sanjay Lake and the pipeline carrying it had developed leakages a while again.” Restore work, the official added, was being taken up by DJB and is more likely to be accomplished shortly.
The incident has revived issues flagged earlier by the Nationwide Inexperienced Tribunal (NGT). In a 2022 order, the NGT had famous that Sanjay Lake, positioned 3-5 km from the Ghazipur landfill, confirmed excessive Chemical Oxygen Demand (COD) values, indicating that the water carries a heavy air pollution load, which might cut back oxygen availability and make the water hostile for fish and different aquatic life.
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The NGT report had pointed to the necessity for additional examination of doable sources of contamination across the lake – additionally identified to draw native and migratory birds – whereas noting native drains and sewage inflows as doable contributors to the deteriorating water high quality.
An evaluation carried out by Delhi Air pollution Management Committee (DPCC) on Kondli STP in April had discovered outlet samples to be “assembly requirements”.
But, the lake on Thursday confirmed seen indicators of stagnation and contamination. In a number of pockets, the water appeared blackish-green and darkish slush lined its edges.
Environmental consultants mentioned low water ranges throughout a heatwave could outcome in pollution changing into extra concentrated. Increased temperatures additionally cut back the flexibility of the water to carry dissolved oxygen, whereas decomposing natural matter and waste eat extra oxygen. Collectively, these circumstances can set off a sudden crash in dissolved oxygen, resulting in fish deaths.
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Bhim Singh Rawat, a Yamuna and waterbody skilled, mentioned a number of incidents of mass fish mortality had been seen over the previous month in the Yamuna upstream of Delhi and in related waterbodies, together with Sahibi river channel and Sanjay Lake.
In line with wildlife fanatic Yatin Verma, mass fish deaths have been reported this April-Could in Sahibi river or Najafgarh drain, which carries Yamuna water.
“There are a number of components at play. Within the Najafgarh case, the difficulty is primarily as a result of sudden launch of untreated effluents from stormwater drains and Dhansa regulator. In Sanjay Lake, it seems to be like a case of sharp decline in water stage as a consequence of excessive temperature. The lake’s water high quality is additional deteriorated by unabated air pollution and dumping of stable waste in enormous quantities,” Rawat mentioned.
He mentioned such incidents happen repeatedly in the Yamuna and its tributaries throughout summer time, when contamination overtakes recent water availability in water our bodies, ensuing in a pointy decline in oxygen ranges. “The rising temperature alone shouldn’t be blamed. Authorities businesses chargeable for sustaining freshwater move and controlling air pollution have failed on each fronts… They’ve change into mute spectators to the continued perishing of treasured aquatic species in Yamuna,” he added.
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Verma, additionally a researcher based mostly in NCR, mentioned he sees fish deaths in Sanjay Lake and Sahibi river channel yearly, however the scale this 12 months appeared a lot greater. “This 12 months it was like a flood… lots of of dead fish floating on the floor, one thing I’ve by no means seen earlier than,” Verma mentioned. “The water seems to be degrading quickly. It impacts not simply fish, however birds that feed on them, and doubtlessly even groundwater at factors the place this water seeps into the bottom.”
The DPCC’s April water-quality report for the Yamuna has additionally proven the broader ecological stress on the river system. Dissolved oxygen was recorded as ‘nil’ at a number of downstream places, together with ISBT bridge, ITO bridge, Nizamuddin bridge, Hindon lower, Okhla barrage and Asgarpur, whereas the Organic Oxygen Demand (BOD) ranges have been far above the Class C criterion (water match for out of doors bathing) at a number of factors. Individually, the DPCC’s April drain-monitoring report for the Najafgarh system recorded a number of drains with BOD ranges above the prescribed commonplace of 30 mg/l.
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