Why are many lakes in Bengaluru green? It is because they are blanketed by microscopic plants that contain chlorophyll, called algae. But are they good or bad for the lakes?
Fixers of carbon, generators of biomass and inconspicuous primary producers in the ecosystem – algae are vital for healthy lakes. These microorganisms convert water and carbon dioxide to sugar, through the process of photosynthesis. This generates oxygen as a by-product.
Zooplankton, small fish and other aquatic creatures, consume algae launching the magical process of the food cycle. But too much of a good thing can also be a bad thing. Excess algae, especially the harmful types, can be detrimental to the lake, indicating pollution and high amounts of nutrients like nitrogen and phosphorus which cause eutrophication. The overgrowth of algae can also cause ‘dead zones’ in the lakes, where aquatic life cannot survive because of insufficient oxygen.
In Bengaluru, the discharge of industrial waste and untreated sewage, algal blooms (rapid increase in the population of algae) occur. The water then gets polluted, discoloured, clogged and gives out a certain odour.
A lake’s beauty comes from the biodiversity it hosts, its calm waters and views. But in recent times, ‘beautification’ in the urban context, is associated with artificial structures and concretisation. Landscaping, boating, paved pathways, and restricted entry through ticketing are some of the elements of the brick and mortar beautification of Bengaluru’s lakes, while activists call for use of the funds for regular rejuvenation through actions like desilting, de-weeding and sewage management.
Environmental activists argue that instead of solely focusing on the superficial beautification of water bodies, the plan should be to restore them and maintain them. Because, by simply beautifying the lakes, the development projects end up shrinking the size of the lakes, by destroying the wetlands surrounding the lake and also have a deleterious impact on the health of the lakes. Excess concretisation and planting non-native, instead of native trees and plants typically found around the lake, affects biodiversity.
Round, light-weight boats – coracles – are a reminder of Bengaluru of yore. Before a joyride on a coracle became a tourist attraction, these boats were widely used by fisherfolk for traditional and sustainable fishing. Fishing communities used the coracle to spread nets and harvest fish. The practice is less popular now as urbanisation has changed the landscape and fishing practices have been modified too, though fishers still use coracles made from synthetic materials instead of natural materials. The coracle remains a symbol of the journey of Bengaluru lakes from fishing hotspots to recreational sites.
Buzzing around Bengaluru lakes, dragonflies are often on a hunt for insects on the lake. These speedy fliers spend most of their life near water bodies and are part of the lake ecosystem in Bengaluru. The larvae live in water and the adults are terrestrial and find their food by the water.
Millions of dragonflies migrate thousands of kilometres across the sea each year, from southern India to Africa. Biologists claim that this could be the longest migration of any insect. Their presence is very important for humans too. Being aerial predators, they catch unwanted insects like mosquitoes and feed on them. They also catch midges, butterflies, moths and bees.
Effluent is wastewater containing a high amount of toxins that flow out of factories, industries or sewer plants, directly into water bodies. Effluent discharge into freshwater ecosystems like lakes, affects the water, reducing its oxygen content and making it unusable. It also affects the soil that is fed by this toxic water. The poor water and soil quality in turn are harmful to plant and animal life that survive on them.
Effluents are also one of the elements of the froth – bubbles of water that form a white layer on lakes. Due to effluents, non-biodegradable detergents and other toxins present in the lake, the lakes belch out froth. Bengaluru’s Bellandur lake, infamous for its pollution, has been found covered with a huge amount of smelly froth. The fluffy white frothy layer on a lake is actually a sign that the lake is unhealthy and needs immediate restoration attempts.
Groundwater is the water present beneath the Earth’s surface. In Bengaluru, one of Asia’s fastest-growing cities, groundwater is not available in abundance to meet the water demand. Bengaluru’s annual average rainfall is 970 mm. Well, that seems sufficient to meet our needs! Yes, but in many parts of the city, the groundwater is contaminated due to sewage, industrial waste and soil pollution, making it unusable/unsafe. Conserving groundwater needs action by both the citizens and the government who together need to ensure that groundwater recharge is carried out at scale across the city.
Public spaces are what give character to a city. Bengaluru has evolved to become synonymous with lakes because of how successfully people utilise the space. Lakes in Bengaluru are reminders of a childhood spent in the company of nature. The greenery, the water and the biodiversity in and around the water source, people in their calmest moods, make the time spent by the lakes, a relaxing affair. A lake is a place of many ‘Hellos’ – familiar hellos and new hellos. Here, friendships are formed, much-needed alone time is sought, communities come together and outdoor recreation is pursued.
With its long, downward-curved bill, the ibis is easily recognisable. It usually inhabits wetlands and plains. The red-naped ibis (left) is a regular at Bengaluru’s lakes. The wetlands are also home to the black-headed ibis and the glossy ibis. Waterbirds like cattle egrets, pond herons,the Eurasian spoonbill, spot-billed pelicans, cormorants and painted storks are other birds who depend on Bengaluru’s lakes, offering many sights for birding enthusiasts and citizen scientists.
The lakes of Bengaluru once also hosted jackals in huge numbers. The shrinking green spaces and water bodies have led to their numbers dwindling as well. Jackals are primarily scavengers, although they are also known to prey on birds, rodents, and other small animals. Snakes, jungle cats, mongooses and slender lorises are some of the other urban wild residents of Bengaluru.
Kere (ಕೆರೆ) is ‘lake’ in Kannada, the language predominantly spoken in the state of Karnataka. Since the city does not have a perennial river running nearby, and the water dependency lies on Cauvery which is also very far, keres in Bengaluru are an integral part of the culture, economy and history. Some of the popular lakes are Sankey tank, Madivala tank, Bellandur lake, Chele kere, Hebbal lake, Ulsoor lake, Varthur kere, Jakkur lake, Akshayanagara kere and Benniganahally tank. Wetlands like kere are productive and biodiverse ecosystems within themselves but remain unappreciated in spite of the important role they play and their numerous benefits.
You will occasionally hear the Kannada term kere habba which means the celebration of the lakes. Such celebrations are now a way to spread more awareness about the conservation of the lake and bring the community together to be actively involved.
The city also has a wide number of smaller water bodies – gokattes (defined as water bodies of between 1 and 3 acre) and kuntes (defined as water bodies less than 1 acre) – which have been around for centuries. Kattes and kuntes are important for water security, biodiversity and flood prevention. According to a 2018 inventory by the Environmental Management and Policy Research Institute report, 57.5% of gokattes and 75% of kuntes of Bengaluru have disappeared.
What does a healthy lake look like? Apart from the impressively balanced ecosystem, the waterbody also provides livelihood opportunities for the citizens. With the proper rejuvenation of lakes, livelihoods can be protected too. Farmers, foragers, fisherfolk and artisans depend on the natural resources from healthy lakes. Livestock can graze in the grass of healthy lakes, fishes thrive, plants and trees provide the means of income for farmers and foragers, artisans collect clay and mud for crafts. There are so many people who depend directly on the lakes for their livelihood and there are many others who depend indirectly too. The revival of lakes thus must factor in the protection of livelihoods too.
Do you feel like the city is getting hotter and hotter each year? It’s partly because of a phenomenon called Urban Heat Island (UHI). An ever-expanding, burgeoning city like Bengaluru is home to many residential areas, offices, industries and recreational spaces. When we keep replacing natural spaces like green covers, lakes and other wetlands with dense concrete, glass and steel structures, the temperatures in the city become warmer than the surrounding areas.
A microclimate is the climate of a small specific area. Lakes play an important role in managing the micro-climate of areas. They maintain atmospheric temperatures and reduce the impact of the UHI effect.
Some lakes of Bengaluru are havens for nesting waterbirds. Resident birds and summer visitors nest in the greenery on the fringes or the vegetation or on the mini islands in the lakes. The birds depend on the smaller animals, insects and plants around the wetland to feed their chicks. Grey-headed swamphen, pond heron, cormorant, little grebe, spot-billed pelican, and painted stork are some of the birds that use the lakes of Bengaluru to nest. Rampant urbanisation, and the loss of surrounding trees, in particular, threatens the nesting habitats.
Just as humans need oxygen in the atmosphere to breathe, fish and some other organisms need oxygen in the water to breathe. The oxygen from the atmosphere dissolves in the water and this is called Dissolved Oxygen (DO). Adequate DO is a good measure of a lake’s quality. If the DO in a lake drops, the aquatic life suffers, shrinking the biodiversity of the area. The discharge of waste into the water can deplete dissolved oxygen content, killing fish and other aquatic life.
The quality of public space has a direct impact on the lives of people and the way they feel. Effective, sustained public action has made a huge difference in the revival of many damaged lakes in Bengaluru. The story of Jakkur lake set an example for the success of inclusive rejuvenation projects. The fisherfolk became the crucial stakeholders and took charge to better the lake. Working together can help restore many lakes to their original state and also help many people protect their livelihoods.
In a bustling city like Bengaluru, the tanks and lakes offer momentary quietness. The calm waters, the excited and curious birds, and the trees and plants that cushion the area from the urban din provide relief from the noise pollution in the busy metro.
Most of the lakes in Bengaluru are artificial lakes, called tanks. They have been built and maintained for several centuries now and receive water from rains. The lakes are linked by a network of natural or human-made channels or stormwater drains, known as raja kaluves, which transport surplus water from higher elevation lakes to lower elevation lakes. Encroachments, dumping of waste or diversion of these channels cause overflow and can lead to flooding during rains.
Soppu are different types of green leafy vegetables and are an integral part of Karnataka’s cuisine. Soppu are found in the natural growth around the lakes and wetlands in Bengaluru, and many foragers and farmers collect the greens to sell them. Healthy lakes encourage healthy greens and support livelihoods. These greens are also locally consumed and form an important part of the nutrition requirements for poorer families. They are also known to have some medicinal uses.
Sewage and garbage dumping has deteriorated much of Bengaluru’s lakes, adversely impacting biodiversity and means of income for many. At lakes that have been revived or where sewage has been diverted away, there is once again the opportunity for income for those who gather and sell soppu.
India has around 29 native species of freshwater turtles and tortoises. Bengaluru’s lakes are home to some of them, such as the Indian black turtle (Melanochelys trijuga) (top), which is a native species found in the city’s lakes. Turtles are important to maintain a healthy lake ecosystem.
But not all turtles are healthy for these lakes. The red-eared slider turtle (Trachemys scripta elegans) (below), found in the city’s lakes too, is an invasive species. The exotic and popular pet is often released into the wild by pet owners and it becomes a threat to the native turtles by competing for food and nesting space and even spreading diseases. With more than 50 percent of freshwater turtles threatened with extinction, conserving lake habitats is vital.
Bengaluru is the capital city of the state of Karnataka and the third most populous city in India. With the growth of the IT sector and the expansion of the city, natural spaces have shrunk. Urbanisation, though inevitable and needed in the process of modernisation, comes at the cost of many a lot of natural resources.
There is ample evidence of encroachment and pollution of water bodies due to excessive urbanisation. The economic growth has had a major impact on the ecosystem in Bengaluru as green spaces have turned into building complexes and the lakes have shrunk in numbers and sizes. The lakes either get built on or are used as dumping grounds for waste and construction debris, killing the lake. Now, both government and non-governmental organisations are working to improve the conditions of the lakes in Bengaluru.
Vrishabhavathi is a river that flows through the south of Bengaluru, past 96 of the 198 wards of the municipal corporation. A 17th century Nandi statue at a temple in the Basavanagudi area of Bengaluru, has mentions of the river originating from the feet of the statue. The once pristine river used as a drinking water source is now deteriorating and is heavily polluted. Currently, lakes drain into this river and untreated sewage let into lakes ultimately flows into the river too. Vrishabhavathi eventually winds out in the Arkavathi River, carrying the trash of the city and damaging water supplies downstream.
What’s the new drought mitigation strategy to help Bengaluru survive tougher summers? Wastewater Treatment. Treated wastewater from sewage treatment plants is being pumped into the city lakes. Currently treated wastewater is let into Doddakere, Sihineerkere and Bettakote lakes. An initiative of the Minor Irrigation Department, this pumping of treated wastewater will ensure that the lakes don’t go dry. MID monitors the water level in the lakes. Farmers are also very happy about this initiative as it has led to an increase in the yield of borewells after decades.
Wastewater is also purified by natural wetlands, which are widely found in Bengaluru. Wetlands are known as the “earth’s kidneys” for the role they play in filtering pollutants from the water that flows in them.
Xylocopa is a carpenter bee genus with many species native to Asia. Widely found in Bengaluru’s lakes, these solitary bees hibernate during winters and emerge around spring time. Carpenter bees, as their name suggests, carve holes into wood or bamboo with their powerful mandibles. Xylocopa’s wings are iridescent due to light refracting through nanostructures in their wings.
The carpenter bees and other species of bees are essential for lake ecosystems because they help in pollination. Bee-eaters and other birds consume these bees. The bees thus support the entire food chain with their presence.
Eri (pronounced as yeri in Kannada) is a bund or structure covering a waterbody. It is usually a low embankment that controls the runoff of water and helps in water storage. Bunds can be naturally made up of soil or artificial with rocks and cement. In Karnataka, there have been incidents of lake bund breaches in the past, which have resulted in the inundation of many areas. Eri maintenance, therefore, is vital. In Bengaluru, many bunds were constructed while planning the city, way back in the 16th century and are both historically and ecologically important.
Zooplankton is a group of microorganisms that are important because they are the source of food for aquatic creatures in the lakes and other waterbodies. They are the bio-indicators of a healthy lake because they maintain biodiversity and act as a link between primary producers and higher trophic levels.
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