Conclusion

Lakes of Bangalore, as our studies reveal, are in gravely polluted condition due to the following reasons:

• All the 17 lakes studied had not shown significant changes in their outlet waters, which are as impure as their inlets, since these lakes are challenged beyond their self purification capacities. The ANOVA analysis shows no significant variation between inlet and outlet waters. Our findings clearly show that macroinvertebrates diversity, abundance and trophic categorizations are almost same in both inlet and outlet locality of the urban lakes of Bangalore.
• Increased input of urban sewage and other urban wastes have raised the nutrient concentrations of these lake waters creating eutrophic conditions.
• Important environmental parameters like phosphate, nitrate, alkalinity, chloride, biological oxygen demand and turbidity, the harmonious balance of which are decisive in the upkeep of pristine aquatic ecosystems, were in an utter state of disorder, as indicated also by the existing macroinvertebrate diversity in these lakes.
• The abundant presence of macroinvertebrate indicators of water pollution, such as Micronecta sp., and Chironominus sp., in the outlet waters also is indicative of the failure of the self purification capabilities of these lakes studied.
• The dense growth of floating water weeds, especially Eichhornia, Pistia, Lemna etc., along with several other tall dicot herbs, grasses and sedges that grow along the shallow parts of the lakes, have caused depleted oxygen levels in many weeds
• The entry of industrial pollutants in Bangalore lakes have been documented in many earlier studies also (Ramachandra et al., 2000; Lokeshwari and Chandrappa, 2006; Ramachandra and Solanki, 2007; Alakananda et al., 2011).

In brief it may be stated Bangalore and suburbs had a glorious past as regards the number of lakes and quality of their waters were concerned. Many of these lakes have already vanished under urbanization and many remaining ones are in precarious state. Water bodies being the lifelines of humanity utmost care need to exercise in protecting the lakes of Bangalore from encroachments and their water quality needs to be improved steadily through appropriate management interventions, specific to each lake.