Water hyacinth, a floating water plant has formed a dense mass in Powai lake. Situated in Powai valley to the south west of Vihar lake. It overflows into the Mithi river. It overflows every year for about sixty days i.e two months. The lake is deepest i.e 12 meters(39 fts) inside and 3 meters (9.8fts) towards its periphery. It has a catchment area of about 6.61 swim and surface elevation of 58.5 meters (191.93fts).Area of the lake is about (2.1 sq km) of which 15% has been encroached upon by water hyacinth. This has hindered the sunlights to reach aquatic lives below water surface.
The decay process depletes dissolved oxygen ((D.O) of water causing death of fish and other aquatic animals.
Water hyacinth is also supposed to be a good breeding ground for mosquitoes which are vector of disease. A parasitic flatworm which lives on snail cause snail fever is an ideal reseller of water hyacinth.
Causes : Cause of growth of water hyacinth are many , but the main cause is excessive sewerage disposal. On the back side of lake, there is a slum , from where the sewerage goes directly into the lake.Large silt deposits and garbage from in and around the area pollutes the lake and makes it unfit for drinking.
Control measures : Use of herbicides such as 2,4-D Glyphosate and Diquat ( liquid bromide) are sprayed as control measures. Glyphosate has lower toxicity than Diquat . It takes about two weeks for Glyphosate to kill the weed plants , while Diquat can cause quick cellular apoptosis ( cell death).
Suggestions : Skilled technicians and strict government approval should be taken to spray these herbicides. In this case , the alternative is biological control method . Use of grasshoppers ( for lo aquaticum ) can easily destroy water hyacinths. Also the introduction of gold fish which feeds on water hyacinth results in cleaning of lake, which increases the D.O of lake. Yet another suggestion is to divert the sewerage line or stop it completely.
Conclusion : As the untreated waste continues to flush in , water hyacinth remains to be a major problem till date. Inspite of the effort of BMC , which has been continuously removing water hyacinth for the last three years, yet it continues to spread.
*Lake water is non - potable and is supplied to Aarey colony and Larson and Tourbo for non domestic use.