Once upon a lake

A report on Bengaluru’s system of lakes and canal networks highlights how scientific urban planning can result in efficient use of a city’s natural resources, equitable benefit sharing among its citizens, cleaner environments and a richer urban biodiversity. It also illustrates how a well-planned system can develop fault lines if taken for granted.

The report, by ATREE’s Harini Nagendra, Ramesh Sivaram, Federation of Resident Welfare Associations of Ward 150 and Dr. S. Subramanya, ornithologist, expounds on the current status of the water bodies in Bengaluru’s Mahadevpura constituency, and steps that can be taken for informed and scientific reclamation and restoration of these. The report, currently being shared with the Bruhat Bengaluru Mahanagara Palike, under which the management of these lakes is consolidated, aims to inform planning at a constituency and ward level.

Background on Bengaluru’s lake and canal systems

The original network of kere (lakes) in Bengaluru was linked through a web of canals or kaluve, connected to the surrounding agricultural-wetland landscape. The network was made up of numerous tanks, ranging from less than a hectare in size; to medium sized tanks of tens of hectares, and a few large tanks of hundreds of hectares in area. All were rain fed. The small and medium tanks were seasonal; only large tanks were perennial.

During the monsoon, the water levels were at their highest. Wetlands, orchards and agricultural fields surrounded the lake, and these were irrigated by water from open wells that were dependent on the ground water table recharged by nearby lakes. Water was used for domestic purposes such as washing, for drinking water, and to replenish the ground water table. Fishing was also done. Idols were immersed in the tanks during festivals. Since most lakes were seasonal, and pollution levels were low, siltation was easy to control. The silt was extracted every few years. The wetland-agricultural-grazing orchard landscape surrounding the lake acted as a natural watershed basin to recharge the lake with fresh precipitation.

What changed

Urbanization has meant that much of the landscape around lakes is now covered by impervious surfaces through which water cannot percolate into the ground. The interconnected lake-canal network is broken, with a large number of the smaller lakes and several of the medium sized lakes converted to other land uses. Only some of the larger lakes remain. The kaluve are encroached. Instead of rainwater precipitation, sewage and effluents fill the lakes, converting them from seasonal to perennial ecosystems and drastically altering their biodiversity. In low rainfall years, the lakes dry up and become choked with sewage; in high rainfall years they overflow into blocked kaluve, and result in flooding in the city.

Criteria for recommendations

There are 35 lakes in 10 sub chains in Mahadevpura of which ten lakes are completely dry and fifteen are heavily polluted. Eight are in healthy condition, but require protection from sewage. Two have been restored. The report suggests individual strategies for each lake based on their current status and most compelling damaging circumstances. The report considers lake size, drainage pattern, connectivity, land use and vegetation, biodiversity, and patterns of human use.

The strategies for restoration and management consider lake benefits for ground water recharging, acting as green spaces, lung spaces, areas for microclimate, supporting biodiversity, providing areas for exercise and recreational use, educational opportunities to expose urban residents and youth to nature and ecological principles, and important cultural, sacred and livelihood uses for local communities.

Recommendations

1. Unblock water flows. Remove encroachments and clear kaluve of blockages. Sewage should be treated by biological control, diversion, and treatment through STPs at each sub-chain. For reasonably healthy lakes, clear kaluve and divert sewage.
2. Dredge severely polluted and dry lakes.
3. Maintain variations in depth of the lake so as to create diversity of water habitat and therefore encourage different fauna and flora. Employ appropriate greening around the lake.
4. Prevent disturbance to biodiversity. Ban motorized boats and keep walking and bicycling paths away from marshy, diversity-rich areas of the lake.
5. Recognise citizen rights. Lakes constitute public commons and should be accessible to all. Several of the lakes do not have public access at present and are completely surrounded by private land owners.
6. Provide opportunities for traditional use and use by urban poor, including for washing of clothes and cattle, and controlled harvesting of grass.
7. Form Ward Task Forces involving local communities, corporators, MLAs, BBMP, Forest Department, BWSSB, schools and colleges, researchers and NGOs to monitor, maintain and regulate lake condition.