PANAJI: The lakes are dying a slow death thanks to rapid growth and urbanisation resulting in encroachment and discharge of sewage and industrial effluents.
The water monitoring study carried out by the Goa State Pollution Control Board on eight major lakes of the state found them highly polluted.
The study found 90% of the lakes were sewage-fed due to sustained flow of untreated sewage and industrial effluents, dumping of solid wastes and building debris.
According to Central Pollution Control Board (CPCB) guidelines, levels of Biochemical Oxygen Demand (BOD) – the concentration of oxygen required for aquatic life – above 3 mg/L cannot sustain fish species. However, a study done between April 2017 and March 2018 by scientific team of board found that BOD levels in four out of eight lakes were between 8 and 23 milligrams per litre (mg/L).
The BOD levels of Mayem, Carambolim, Selaulim and Anjunem lakes matched the prescribed limit but the faecal coliform was found at high levels of 4900MPN/100ml except for Selaulim and Anjunem which show the pollutant in fewer limits between 14MPN/100ml and 45MPN/100ml.
Saipem Lake in Navelim was identified as the most polluted lake in the state with low levels of dissolved oxygen and high levels of Biochemical Oxygen Demand (BOD) which is severely affecting the aquatic life.
Similarly the pollution levels at the Raia lake are above the safe limit and the deteriorating water quality could endanger aquatic life. It recorded maximum amount of faecal coliform levels of 11000 MPN/100 in November, and recorded lowest of 230 MPN/100 ml during the summer season. The BOD levels also exceeded permissible limit between April and June and also in February this year.
The BOD levels at the Rumder Lake in Nuvem exceeded the safe limit in May last year and between January and March this year. It also recorded faecal coliform at high levels between 1300-7900MPN/100ml and as low as 200 MPN/100ml was recorded in January this year.
The pollution level in Curtorim lake caused due to sewage discharge was recorded between 450 MPN/100 ml and 7900 MPN/100 ml during the winter. While the BOD count was high in May and December 2017.