A suitable restoration action plan could be devised only if characterisation of the type and source of pollutants entering the ecosystem is known. Investigation of the physico-chemical and biological parameters in this regard helps in assessing the status, which is required for evolving appropriate restoration methods towards conservation and management. In order to characterise the water quality of wetlands, sample lakes/tanks were chosen in and around Bangalore for monitoring, depending on the location and type of pollutants getting in to the system. Nine lakes were monitored from 1996 to 2000. The investigations revealed that most of the analysed parameters for the lakes (e.g. Ulsoor, Hebbal, Yediur, Kamakshipalya and Madivala) exceeded the limits set by Indian standards for industrial and sewage effluents discharge [IS 2490 -1982].

• The water quality of Kamakshipalaya tank revealed that the tank was highly polluted due to the inflow of sewage and industrial effluents from the neighbouring areas. The turbidity of the water body was high along with parameters like electrical conductivity (EC), dissolved oxygen (DO) and biological oxygen demand (BOD).
• Madivala lake receives inflow of sewage from the surrounding residential areas as elucidated by high values of pH, EC, BOD and COD.
• Yediyur tank receives industrial and domestic effluents, which has given rise to algal blooms, mainly microcystis. Quality monitoring revealed high turbidity, low transparency, alkaline pH, and high sodium, potassium, calcium and magnesium.
• Hebbal tank, situated in the northern part of the city, supports agriculture, fishing, etc. The tank receives untreated sewage from the adjacent residential layouts, contributing to alkaline pH, high EC, high total solids, low dissolved oxygen and high nitrate and phosphates.
• Ulsoor tank receives untreated sewage from the nearby industries and residential layouts contributing to high pollution loads in the tank. The parameters that exceeded the standard values include turbidity, transparency, EC, BOD and COD
• Amruthalli lake, situated in Bangalore North, has attained eutrophic condition (excessive input of nutrients and organic matter from the inflow of sewage, industrial effluents and dumping of organic waste matter from the surrounding areas) evident from high levels of phosphates, TSS, alkalinity, hardness, weed infestation and low DO. Dependency of people residing around this wetland (in financial terms) based on socio-economic surveys was about Rs.20/day. The eutrophic condition of the lake has made this resource unusable. Similar exercise carried out in a relatively clean wetland ecosystem reveals the dependency as about Rs.10,470 per day, which highlights the benefits of cleaner environment.

Most of the lakes in Bangalore city are highly eutrophic (as exemplified by water quality analyses) and demand the immediate attention of civic authorities towards restoration and conservation.