Wetlands/lakes constitute the earth’s most important freshwater resource, supporting huge biological diversity and provide a wide range of ecosystem services. Wetlands are highly productive ecosystems as they function as eco-tones, transition zones between different habitats, and have characteristics of both aquatic and terrestrial ecosystems. Wetlands are also the most threatened and fragile ecosystems that are susceptible to changes owing to changes in the composition of their biotic and abiotic factors (Ramachandra, 2005). They help in maintaining the ecological balance of the region and meets the need for life on the Earth such as source of drinking water, fish production, storage of water, sediment trapping, nutrient retention and removal, ground water recharge and discharge, flood and erosion control, transport, recreation, climate stabilizers, support for food chains, habitat for indigenous and migratory birds, etc. Wetlands/lakes also play a major role in treating and detoxifying a variety of waste products (Kiran and Ramachandra, 1999; Ramachandra and Solanki, 2007). Wetlands aid in remediation and aid as kidneys of landscape.
Wetland loss and degradation are due to conversion of wetland to non-wetland areas, encroachment of drainages (raja kaluves) through land filling, pollution due to sustained  discharge of untreated domestic sewage as well as industrial effluents and dumping of solid waste, hydrological alterations (water withdrawal and inflow changes), and over-exploitation of their natural resources. These anthropogenic activities results in habitat degradation, weed infestation due to nutrient enrichment, loss of biodiversity and decline in goods and services provided by wetlands (Ramachandra, 2010). Pollution of water bodies is due to:

The entry of untreated sewage into lakes has resulted in nutrient enrichment leading to eutrophication with algal blooms and macrophytes cover with dissolved oxygen depletion and malodor generation (Mahapatra et al., 2011). Land use and land cover (LULC) changes in the wetland catchment alter the physical and chemical integrity of the system, which influences the biological community structure of the area (Ramachandra et al., 2013).

Greater Bangalore with an area of 741 square kilometers lies between the latitudes 12°39’00” to 13°13’00”N and longitude 77°22’00” to 77°52’00”E. Bangalore is located at an altitude of 920 meters above mean sea level, delineating into three watersheds namely, Hebbal, Koramangala-Challaghatta and Vrishabhavathi watersheds. The undulating terrain in the region has facilitated creation of a large number of tanks (mainly attributed to the vision of Kempe Gowda and of the Wodeyar dynasty) providing for the traditional uses of irrigation, drinking, fishing and washing (Ramachandra and Kumar, 2008; Sudhira et al., 2007). Wetlands of Bangalore occupy about 4.8% of the city's geographical area (640 sq.km) covering both urban and non-urban areas. Bangalore has many manmade wetlands but no natural wetlands (Ramachandra and Ahalya, 2001). In 1973, Greater Bangalore had 207 water bodies, which has now reduced to 93 (by 2011), many lakes (54%) were encroached for illegal buildings (Ramachandra et al., 2013). Earlier field investigations had revealed that nearly 66% of lakes are sewage fed, 14% surrounded by slums and 72% showed loss of catchment area. About 30% of the lakes were drained for residential sectors. About 22% of lakes had land filling and construction activities. Now, lake beds are being used as dumping yards for either municipal solid waste or building debris (Ramachandra, 2010). The storm water drains, lake beds, flood plains and catchment areas have been encroached and converted to layouts or for commercial purposes. In case of Bangalore, a decline of vegetation by 66% and water bodies by 74% has been noticed with 584% growth in built-up area during the last four decades (Ramachandra et al., 2012). Recent studies reveal of 925% increase in built-up area with decline of 78% vegetation and 79% water bodies.

Water demand in Bangalore is roughly about 150 liters per day (lpd) per person and the total water requirement for domestic purposes is about 1,400 million liters per day (MLD). Water available from Cauvery (Stages I to IV, Phase I) and Arkavathy (Hesarghatta and Tippagondanahalli reservoirs) rivers is about 975 MLD. The loss of water during transportation and distribution is assumed to be ~30%. These indicate that there is a high demand for water/water scarcity in Bangalore (Ramachandra, et al., 2014). Functions of wetlands are listed in Table 1. Wetlands/lakes help in preventing frequent flooding and micro–climatic changes in the city. The decline in number of water bodies due to industrialization and urbanization had brought about many undesirable effects/impacts on water quality, diversity of flora and fauna and affected the livelihood of dependent population (fisherman, dhobis, etc.). There has been a decrease in the number of migratory birds. Wetlands capture rainwater efficiently and help in ground water recharge apart from aiding in the treatment as kidneys of the landscape. There has been a rapid increase in the number of bore wells in Bangalore over the last three decades from 5,000 to around 4.08 lakh. About 40% of Bengaluru populations are dependent on 750 MLD of ground water (Ramachandra, et al., 2014). The water scarcity issues in Bangalore city can be tackled if the lakes are well/properly maintained to satisfy the needs of the people.

Table 1: Importance of Wetlands/Lakes

According to Bruhat Bangalore Mahanagara Palike (BBMP), Bangalore city had lost many lakes due to developmental activities such as residential layouts, playgrounds, stadiums, industries, government buildings and bus stands. Lakebeds now are dominated by private projects, apartments and houses etc. (table 2).

Table 2: Lost wetlands of Bangalore

The Bangalore Water Supply and Sewerage Board (BWSSB) is mandated to provide drinking water and  treat the sewage generated in the city. Unfortunately, BWSSB has been transporting partially or untreated sewage to lakes. Due to this irresponsible act of para-state agency, existing lakes have been reduced to cesspools with the sustained inflow of untreated sewage. Coupled to this, untreated effluents from industries and dumping of solid wastes have further compounded the agony. Unplanned urbanization, lack of co-ordination among para-state agencies and enhanced anthropogenic activities have resulted to (i) the loss of interconnectivity among wetlands (due to encroachments of storm water drains and Raja kaluves, (ii) senseless conversion of wetlands, (iii) nutrient enrichment and heavy metal contamination in wetlands, (iv) increased episodes  of floods, (v) dumping of solid wastes and building demolition debris, etc.

The shortfall or lack of sewage treatment facilities is the prime causal factor for contamination of surface and ground waters. The sewage treatment plants (STPs) can remove contaminants (Carbon and solids) from sewage water. BWSSB has commissioned STPs (table 3) in recent times. But the treatment efficiency is low, so a substantial part of the sewage goes untreated which makes lake water polluted. But, the introduction of an integrated wetland system as in JAKKUR Lake (consisting of sewage treatment plant, constructed wetlands with location specific macrophytes and algal pond integrated with the lake) helps in the complete removal of nutrients in a cost effective way (Ramachandra et al., 2014).

Table 3: STPs at Bangalore

(Source: http://cseindia.org/userfiles/bangaluru_portrait.pdf)

The aquatic conservation strategy should focus on conservation and maintenance of ecological health of aquatic ecosystems to maintain the aquatic biodiversity in the region, maintain inter-connectivity among lakes, and preserve its physical integrity (shorelines, banks and bottom configurations) and water quality to support healthy riparian, aquatic and wetland ecosystems. The regular monitoring of water bodies involving students at school, college and research institutions, and also public awareness will help in developing appropriate conservation and management strategies (Ramachandra et al., 2005).
The agencies that undertake conservation, restoration and maintenance of wetlands in BBMP area are Bangalore Water Supply and Sewerage Board (BWSSB), Bangalore Development Authority (BDA), Bangalore Metropolitan Regional Development Authority (BMRDA), Bangalore Mahanagara Palike (BBMP), Lake Development Authority (LDA), Minor Irrigation Department and Karnataka Forest Department.
The important recommendations suggested through Lakshman Rau committee report, emphasizing the preservation and restoration of existing tanks in Bangalore in 1988 are:

Privatization of lakes in Bangalore: Livelihood of wetland dependent population and ecology research received major blow with the ill-conceived programme implementation under "public-private partnership" of LDA (Lake  Development Agency) in 2004.

LDA began a process of "public-private participation" in 2004 where, private companies bid for the lakes to develop, beautify and maintain lakes under Develop/Operate/Transfer (DOT) or NON-DOT basis for the next 15 years. The private partners can be interested private/public participants, including Registered NGO’s, Corporations/Business Houses/Resident Associations etc. These private partners can be involved in the conservation of lakes and allowed to operate recreational facilities in return for conserving and maintaining the lake. The private partner shall be responsible for desilting, dredging, landscaping, sewage diversions, foreshore and island development, building of walkways and jogging paths, creation of tree parks, rock gardens, children park area, cycling tracks, fountains, electrification for illumination etc. They can be allowed to construct boat jetty, sports fishing, bird watching, Butterfly park, boating, eco-friendly water sports, eco friendly restaurants etc to generate revenues to make the project financially viable (Thippaiah, 2009; Lake Conservation, Karnataka). Some privatized lakes in Bangalore are Hebbal lake, Nagavara lake (also called Lumbini Gardens after privatization) and K.R. Puram lake or Vengaiahna kere (also called Fantasy Lagoon, or Hagalu Kanasina Kere, after privatization). In May 2004, LDA leased out the Hebbal lake to East India Hotels Ltd (Oberoi group) for a period of 15 under the Public-Private Partnership policy.The Nagavara lake was leased to Lumbini Developers in 2004 for a period of 15 years and Vengaiahnakere was leased to Par C Ltd. The privatization of lakes has severely impacted the natural ecosystem due to:

• increased commercialization of public/natural assets,
• construction of theme parks, entertainment venues and shopping malls affected natural ecosystem,
• violation of land use regulations by the private partners during implementation of the scheme,
• denying access to dependent populations for washing, bathing; for fodder; fishing, irrigation, recreation, etc.,
• poor water quality (due to lack of maintenance) and impact on flora and fauna

The common threats (figure 1, table 4) faced by lakes in Bangalore include a) dumping of building debris, plastic and solid waste into lakes, b) constructing buildings illegally near or on the lakes by the developers/agencies, c) improper and damaged fencing which will increase encroachments in the area, e) inflow of untreated sewage into lakes from surrounding households, apartments, companies, industries etc. and f) filling the lake area of abandoned lakes. The mismanagement of municipal solid waste management in Bangalore has affected the local environment, which is evident from illegal dumping of solid wastes and building debris in lake beds, open drains, parks and open spaces, etc. The leaching of organic fraction of solid waste contaminates land and water (Shwetmala et al., 2012).

Figure 1: Common threats faced by lakes in Bangalore: a) Dumping of building debris, b) plastic and solid waste dumping, c) constructing building near the lakes, d) improper and damaged fencing, e) inflow of untreated sewage into lakes and f) filling the lake area of abandoned lakes.

Table 4: The common threats faced by lakes in Bangalore are:

The main consequences faced by lakes (figure 2) due to anthropogenic activities include a) profuse growth of algae and macrophytes due to nutrient enrichment. This leads to oxygen depletion in lakes, affecting aquatic flora and fauna (example, fish death), b) lake will eventually dry up due to accumulation of silt and organic sediments. This reduces the water holding capacity of the lakes and also contaminates ground water, c) The disposal of solid and liquid wastes to the lakes makes water black in color with stinking environment, d) Foams are formed in lakes naturally when algae and fish, die and decompose, releasing a variety of organic compounds into the waterbody. The surface-active agents in wastewater include synthetic detergents, fats, oils, greases and biosurfactants. These act as surfactants and reduce surface tension among water molecules. When air mixes with water molecules vigorously, foam formation occurs. Bellandur and Varthur lakes faced severe froth formation and also  fire (Ramachandra et al., 2015b).

Figure 2: The consequences faced by lakes due to anthropogenic activities: a) fully covered with macrophytes, b) fish death, c) profuse growth of algae, d) dried up lake, e) lake with accumulated plastics wastes, f) black coloured stagnant water with stinking environment, g) foam formation, h) fire in lakes and i) accumulation of organic sediments.

Water pollution and health effects: The pollution of fresh water bodies and ground water are harmful for human and animal health. Polluted water may have undesirable colour, odour, taste, turbidity, high total dissolved solids (TDS), nitrates, phenols, salts, harmful chemical contents, toxic and heavy metals, pesticides, oily matters, industrial waste products, domestic sewage content, organic matter contents, bacteria, protozoa, rotifers, virus, worms, etc. These makes the fresh water unfit for drinking and irrigation purposes. Nitrate contamination in drinking water causes ‘blue baby’ syndrome and is linked to digestive tract cancers. Water-borne diseases like Hepatitis, cholera, dysentery, and typhoid are infectious diseases spread primarily through contaminated water. The exposure to polluted water can cause skin irritation, respiratory problems etc. Untreated water provides a habitat for the mosquito and a host of other parasites and insects that cause a large number of diseases. The proper management of water resources can tackle such water-borne epidemics and health hazards.

Water quality assessment includes periodical monitoring of lakes to understand the present status of water bodies, identify and quantify trends in water quality, which will help in understanding the water quality problems as well as contamination status. All these information will help decision makers, resource management groups, regulatory agencies and public to solve water quality as well as water scarcity issues in the state/country and make necessary decisions (Ramachandra, 2009).

The continuous inflow of sewage into lakes results in the prolific growth of macrophytes due to increased levels of nutrient in the system. This restricts sunlight penetration and reduces algal photosynthesis hindering the aerobic environment of lake. Also, the roots of these floating macrophytes harbor bacteria. The high bacterial activity in lakes also reduces DO levels. The overgrowth, ageing, and subsequent decay of macrophytes creates anoxic conditions and depletes oxygen level in lakes which in turn, affects the food chain and the whole aquatic eco system (Mahapatra et al., 2011). The excessive growth/bloom formation of cyanobacteria persists in water bodies that contain adequate levels of essential inorganic nutrients such as nitrogen and phosphorus and increased levels of organic matter. Fish deaths in lakes occur due to water pollution and sudden change in temperature (thermal stress), high ammonia concentrations and hydrogen sulphide, oxygen depletion, diseases and parasite attacks, overcrowded fish population and excessive algae or other plant growth in lakes (Ramachandra et al., 2015). Pollution of water bodies will in turn, affect the aquatic organisms like algae, zooplankton and macrophytes, by bringing about changes in the species composition of the aquatic communities, the dominance of a particular species, decline in species diversity, mortality of some species and sensitive life stages (larvae and eggs).