hyderabad have you ever come across a major lake thats green during winter and bluegreen during summer the water in the 400yearold lake at saroornagar built by the qutub shahis actually changes its colour with the season no there are no special magical powers working here the change in colour from green to bluegreen highlights the extent of pollution in the historic lakewhile many water bodies in hyderabad are plagued mostly by chemical industrial and sewage contamination the saroornagar lake suffers from both heavy metal and biological pollution apart from the invasive eichhorrnia water hyacinth saroornagar lake is dominated by microorganism like zooplankton and phytoplankton to such a high extent that the water has lost its neutral character it is unfit for even animal consumption or washing clothesone set of microorganism takes control of the lake in summer while another group dominates during winterfreefloating eichhorrnia has invaded the lake watersthis symbolises excess nutrient load due to human developmental activities the lake water is green now winter due to the presence of phytoplankton chlorophyceae it will gradually turn bluegreen as summer sets in when another phytoplank ton cyanophyceae will dominate the lake water the oxygen in the lake is insufficient due to chemical industrial biological and sewage pollution the lake stinks says researcher dr k t padma priya from c v r college of engineering hyderabaddr padma priya along with prof p manikya reddy studied water quality at four different points in the lake every month for over 24 months and concluded that the lake is dead due to several factors including eutrophication the size of the water body has also been reduced by half due to encroachmentsthe catchment of the lake has also been encroached uponlakes are vital resources and they regulate the urban climate they also play a crucial role in groundwater recharge sewage discharge improper agricultural practices and urban run offs have disrupted the ecosystem of saroornagar lake said padma priyathe ph of the lake is 837 indicating that the water has turned alkaline she said the chloride content is 7598 milligrams per litre the biological oxygen demand an important parameter for water quality is 2388 mg per litre when it should be less than 6 mg per litre