Conclusion

Bengaluru lakes are under stress due to the mismanagement with the uncoordinated and fragmented governance, which is evident from the sustained inflow of untreated or partially treated sewage, untreated industrial effluents, dumping of municipal solid waste including construction and demolition waste, encroachment of storm water drains and lake bed. Despite the attempts to restore degraded lake to the original status has proved to be futile due to the lack of ecological approaches in the restoration. Multivariate analyses showed that the physicochemical parameters like pH, dissolved oxygen, orthophosphate, nitrate, chloride, calcium, BOD, COD, water temperature and TDS played an important role in determining the water quality of these restored lakes. WQI results revealed only 4 lakes such as Jakkur, Devasandra 1, Ullal and Handrahalli has good water quality. It was noted that Devarabisanahalli lake has very poor water quality before and after restoration activities which shows a lacuna in the current restoration measures. Proper restoration measures should be practiced to control and prevent pollution due to indiscriminate disposal of liquid and solid wastes from domestic and industrial sources into water bodies for improving and maintaining their quality and there is an urgent need to maintain these restored lakes before further deterioration.

Gaps in the current rejuvenation path are (i) lack of understanding of functional aspects of a lake – ecological, hydrological and remediation aspects in addition to recreation services; (ii) the focus of lake rejuvenation is only to utilize the allocated funds (activities matching the allocated funds have been proposed and implemented) without any scientific evaluation of the lake and the need assessment; (iii) not decontaminating the lake – partial removal of contaminated silt (accumulated over a period); (iv) reuse of contaminated silt – shoreline stabilization, creation of ‘islands’. Contaminants in the silt leaches to the lake and maintain the contaminated status of the lake; (v) not arresting fresh pollutants – sustained inflow of partially treated or untreated sewage and industrial effluents; (vi) removal of riparian vegetation and wetlands (which would have removed the nutrients). Riparian vegetation also aids as breeding ground for dependent biota – birds, butterflies, etc.; (vii) emphasis of rejuvenation based on civil works than on ecological restoration; (viii) converting the lake to a ‘cement bowl’ than restoring the ecology of the lake system; and (ix) the focus of rejuvenation is on creating jogging path and beautification of the lake than ecological restoration.

Recommendations

Restoration efforts should reduce pollution, improve the lake water quality and provide habitat, which supports maximum aquatic biodiversity. The following measures need to be adopted to save these restored lakes (table 3):

Table 3: Rejuvenation protocol

Rejuvenation Protocol: Restore to enhance ecological integrity and not to fool public

DECONTAMINATE
  • Complete removal of accumulated contaminated silt in the lake. Desiltation not only enhances storage capacity but also aid in removing contamination. Adopt latest state of the art technology - wet dredging to remove deposited sediments;
  • Scientific approaches in desilting; Remove all accumulated silt considering the original topographic contours;
  • Do not reuse the silt (removed from the lake) for shoreline stabilisation or for creating ‘islands’ as the contaminants get leached to the water, impairing the chemical integrity of an ecosystem;
  • Ensure the complete removal of silt and verification of the achieved depth through scientific survey (total station survey);
  • Implementation of ‘polluter pays’ principle as per the water act 1974; Zero discharge from industries;
  • Stop dumping of solid waste and Construction & Demolition (C & D) wastes in the lake bed, storm water drain; Treat C & D Waste as per C & D waste management rule 2016, GoI;
  • Stop Pollution – only treated sewage shall enter the lake. Sewage treatment through integrated constructed wetlands (similar to Jakkur Model – Secondary Treatment Plant (STP) + Constructed Wetlands + Algae ponds, will remove nutrients, etc.);
  • No diversion of sewage from upstream to downstream regions and
  • Adopt de-centralized sewage treatment option (similar to Jakkur lake – removal of chemical ions and nutrients) and reuse of treated sewage in the locality.

EVICT ENCROACHERS
  • Remove all blockades at outlets as well as inlets– to prevent stagnation of water and enhance aeration in the water body;
  • Remove all encroachments without any considerations or political interventions (lake bed, storm water drains, buffer zone);
  • Remove the nexus of consultants, contractors and engineers.

REGULAR MAINTENANCE

  • Minimum 5 years maintenance of the lake by an agency (who implemented rejuvenation);
  • Remove macrophytes (covered on the water surface) regularly to (i) maintain the water spread area of lakes, (ii) minimise the instances of nutrient re-release to the lake by decay of macrophytes, and (iii) to allow the photosynthesis of algae and improving the trophic level performance.
  • Install fountains (with music and LED) to enhance surface aeration and recreation value of the ecosystem;
  • No introduction of exotic species of fauna (fish, etc.);
  • Identify Local NGO for regular maintenance and management;
  • Public Participation: Decentralised management of lakes through local lake committees involving all stakeholders - Involve local stakeholders in the regular maintenance and management.

MONITORING AND SURVEILLANCE
  • Regular surveillance through vigilant resident groups and a network of local education institutions;
  • Regular monitoring of treatment plant and lake water quality (physical, chemical and biological) and the dissemination of information to the public through internet;
  • Online portal for all urban lakes (with the regular updation of information of water quality, photographic evidences, etc.)

SENSIBLE POLICY & IMPLEMENTATION
  • Shun the path of rejuvenation to siphon off the public funds;
  • Ban on use of phosphates in the manufacture of detergents; will minimise frothing and eutrophication of water bodies;
  • Digitation of land records (especially common lands – lakes, open spaces, parks, etc.) and availability of this geo-referenced data with query based information system to public;
  • Implementation of ‘polluter pays’ principle as per water act 1974;
  • Planting native species of macrophytes in the buffer zone (riparian vegetation) as well as in select open spaces of lake catchment area;
  • Restrictions on the diversion of lake for any other purposes;
  • NO construction activities in the valley zones.

GOOD GOVERNANCE

  • Protect flood plains (buffer zones) to enhance the water retention capability of the lake. Enrich floodplains with riparian vegetation so that water gets treated as it passes through riparian zones;
  • Maintain a minimum of 75 m buffer zone in urban lake and for larger lakes the buffer zone depends on the topography and shape of the catchment;
  • Avoid comparisons with the neighbouring regions (who are in the clutches of land mafia) and reduce the buffer zone;
  • Single agency with the statutory and financial autonomy to be the custodian of natural resources [ownership, regular maintenance and action against polluters (encroachers as well as those who contaminate through untreated sewage and effluents, dumping of solid wastes)]. Effective judicial system for speedy disposal of conflicts related to encroachments;
  • Autonomous status to the agency to ensure minimal interference by the local politicians;
  • Legislators to legislate and ensure effective implementation through the executive mechanism;
  • Efficient decentralised administration through elimination of Land, Water and Waste Mafia.
  • Make bureaucrats and engineers of the respective para-state agencies accountable for the poor status of urban lakes.

FUTURE SCOPE OF WORK

The present work underlines the gaps in the current restoration of lakes in Bengaluru, which will be helpful for different stakeholders and other government agencies who are involved in lake development and watershed management. Implementation of the recommendations would help in improving the local environment conditions. Development of environment health card for all lakes at regular interval would help in mitigating pollution of vital ecosystems.

CONFLICT OF INTEREST AND ETHICAL STANDRADS: We have no competing interests either financial or non-financial.

RESEARCH ETHICS: The publication is based on the original research and has not been submitted elsewhere for publication or web hosting.

ANIMAL ETHICS: The research does not involve either humans, animals or tissues

ACKNOWLEDGEMENTS

We thank (i) UNSD and the Ministry of Statistics and Programme Implementation, Government of India, (ii) The ENVIS Division, The Ministry of Environment, Forests and Climate Change, Government of India and Indian Institute of Science for the sustained support to ecological research.

AUTHORS CONTRIBUTION

  1. Ramachandra T V: Conceptualization and design of experiments; data analysis and interpretation of data, article revision and final editing.
  2. Sincy V: Field monitoring of lakes, carrying out experiments, data analysis and result interpretation and paper writing.
  3. Asulabha KS: Lake monitoring, water quality analysis, data analysis and interpretation and paper writing.