Nutrient load reduction and ecological restoration are the best mitigation strategies for rejuvenation of water quality in the city’s lakes, according to a report of the CSIR-National Environmental Engineering Research Institute (NEERI) submitted to the High Court of Karnataka.
“In many undeveloped lakes, where the external nutrient loading is the predominant factor regulating the eutrophication severity, the control of non-point source pollution is the most effective approach and a variety of best management practices are available to control pollution from urban sources,” the NEERI’s Phase I report stated while analysing the causes for pollution of lakes.
As the inlet to the lake mostly carries sewage along with stormwater, the report suggested the use of two technologies developed by NEERI for treatment of drain water and let the treated water into the lakes.
The report suggested that de-silting and dredging are essential to restore the water storage capacity of lakes. De-silting operations need to be assigned top priority for many lakes, especially for developing and undeveloped lakes, Bellandur and Varthur in particular.
A division bench comprising Chief Justice Abhay Shreeniwas Oka and Justice Sachin Shankar Magadum said that it would consider the report, particularly the restoration plan for Kamakshi Palya, Arehalli and Thavarakere lakes, on Wednesday.
It was observed, the report stated, during the study that many undeveloped lakes are being polluted by solid waste, which include domestic garbage, construction and demolition waste (C&D), agriculture waste and industrial wastes, such as plastic and polystyrene packing materials.
“Conservation and upkeep of lakes need to be given top most priority. Proper maintenance of these lakes helps in groundwater recharge, improves the groundwater quality, helps in rainwater harvesting,” the report said while pointing out that of the 210 lakes, 189 exist and the remaining lakes were totally encroached.