Also, sewage from slums, hotels, and residential areas have polluted the water body affecting its oxygen level and endangering aquatic life
A recent water analysis test carried out at Powai lake by a researcher has revealed shocking results, confirming concerns raised by environmentalists that the lake is dying. While the surface of the lake has turned completely green with algae, the test report reveals exactly how far the water transparency of the lake has fallen.
For the first time in almost 29 years, the transparency of the lake has dropped down to as low as 17.1 cm (In lay man's term meaning reduced sunlight penetration). This is likely to affect the oxygen levels, which in turn may have serious repercussions on the lake's aquatic life.
From a range of 68-120 cms in 1988-89, the transparency readings at the lake have dropped to 17.1-31.5 cms in 2016-17.
Dr Pramod Salaskar, Secretary of Naushad Ali Sarovar Samvardhini (NASS), who has been studying the Powai lake ecosystem for several years now and has conducted water tests too, said that the biggest reason behind the low transparency is the increased growth of blue-green algae, which has also rendered the colour of the lake green. Salaskar also took algae samples for tests and has sent detailed reports of the study to the Brihanmumbai Municipal Corporation (BMC).
Salaskar also mentions a pollution load on the lake, which can be verified by the presence of pollution indicating species such as cyanophycean.
Sunish Kunju of Plant and Animal Welfare Society (PAWS), Mumbai, said, "Sewage is entering the lake from not just slums but also residential areas and hotels in the vicinity. " Kunju also stressed on the need to find the violators and fine them heavily.
A senior BMC official said a proposal has already been passed for reviving the lake and measures will be taken to stop sewage from entering it and work is likely to begin soon.
Transparency (cm) of Powai lake over a period of time:
1988-89: 68-120
1996-97: 51.3- 97.3
2001-2002: 48.5-98.4
2005-2006: 46.8-78.3
2009-2010: 28.9-49.6
2015-2016: 19.4-32.3
2016-2017: 17.1-31.5
May 23, 2016: 18.7cm
May 22, 2017: 17.1 cm
How is transparency of lake water measured (source: MiCorps)
Transparency is commonly measured using a Secchi disk. It gives a direct measure of how deep sunlight is penetrating through the water. One can measure transparency by lowering the disk down into the water until it is no longer visible, noting the depth on the calibrated line, pulling the disk up until it is visible again, and noting the depth a second time.
Why transparency is crucial:
It's a quick and easy way to understand the water quality of a lake. It indicates the depth to which light penetrates in the lake. The plants and algae present in the lake need sunlight to grow and they produce oxygen and are also important as fish feed on them but if the sunlight does not reach them they will die thus reducing the dissolved oxygen content of the water and also affect the fish.
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
 "Powai lake")
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}
)
){kind=small}
){kind=small}
)
)
)
)
)
){kind=small}
){kind=small}
){kind=small}
){kind=small}
){kind=small}