ENVIS Technical Report: 114,  July 2016
   T.V. Ramachandra*       Vinay S      Durga Madhab Mahapatra      Sincy Varghese      Bharath H. Aithal  
Energy and Wetlands Research Group, Centre for Ecological Sciences, Indian Institute of Science, Bangalore – 560012, India.
*Corresponding author: cestvr@ces.iisc.ernet.in
Status of Lakes – Scope for Harvesting Rainwater

The number of lakes in Bangalore has reduced from nearly 285 (1970’s; spatial extent of Bangalore is 161 sq.km) to 194 (2016; spatial extent is 741 sq.km). During the last four decades there has been 79% reduction in water bodies and the number of lakes in Bangalore is given in Figure 8.1.

Figure 8.1: Status of Lake in Bangalore

(Red colour indicate lost lakes between 1970’s to 2016)
During 1800, the storage capacity of Bangalore was 35 TMC. In 1970’s, lakes covered an area of nearly 3180 hectares  and now the spatial extent of lakes cover an area of 2792 hectares. The current capacity of lakes is about 5 TMC and due to siltation, the current storage capacity of the lakes is just about 1.2 TMC, i.e., nearly 387 hectares of water bodies lost apart from reduction in the storage capacity by 60%. Bangalore being located on the ridges, forms three watersheds – Koramangala Challagatta valley, Vrishbhavathi valley and Hebbal Nagavara valley.  Earlier rulers of the region, created interconnected lake systems taking advantage of undulating terrain.  Number of lakes in Koramangala Challaghatta valley is about 81, followed by the Vrishabhavathi valley (56) and the Hebbal Nagavara valley (46).  In order to enhance the water retaining capability in the catchment, it is essential to harvest rain water. Lakes are the optimal means of rainwater harvesting at community level. This entails

  1. Reestablishing interconnectivity among lakes (needs to remove all encroachments without any consideration, as the water security of a region is vital than the vested interests, who have unauthorisedly occupied without respecting future generation’s food and water security. This would also reduce the frequency of floods and consequent damage to life and property,
  2. removal of  all encroachments of lakes and lake bed,
  3. rejuvenation and regular maintenance of water bodies -  this involves desilting of lakes to (a) enhance the storage capacity to retain rainwater, (b) increase the recharge potential – will improve groundwater table, (c) ensure recharging without any contamination,
  4. allowing only treated sewage (removal of chemical and biological contaminants) through adoption of integrated wetlands ecosystem (Jakkur lake model),
  5. creation of wetlands with native vegetation and regular harvesting of macrophytes; food and fodder, which supports local people’s livelihood, and
  6. maintaining at least 33% green cover with native vegetation (grass, trees, shrubs) in the catchment and maintaining riparian vegetation in the buffer region. This would help infiltration of water and retain this water.





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