Green Chemistry & Technology Letters eISSN: 2455-3611, Vol 6, No 1, 2020, pp 14-26 https://doi.org/10.18510/gctl.2020.613 14 |https://giapjournals.com/gctl © Authors EFFICACY OF REJUVENATION OF LAKES IN BENGALURU, INDIA Ramachandra T.V a, b, c * , Sincy V a , Asulabha K.S a a Energy & Wetlands Research Group, Centre for Ecological Sciences, b Centre for Sustainable Technologies (Astra), c Centre for infrastructure, Sustainable Transportation and Urban Planning, Indian Institute of Science, Bengaluru, Karnataka, India. *tvr@iisc.ac.in, envis.ces@iisc.ac.in Article History: Received on 20 th May, Revised on 10 th July, Published on 18 th July 2020 Abstract Purpose of the study: The main objective of the present work is to assess the efficacy of the restoration endeavour in Bengaluru lakes, Karnataka, India. Rapid urbanisation coupled with industrialisation in urban areas has greatly stressed the available water resources qualitatively and quantitatively. This has also resulted in the generation of enormous sewage and wastewater after independence. Method: Environmental monitoring of 40 restored lakes was carried out to identify the key issues and assessed water quality (physical, chemical and biological). Weighted arithmetic water quality index (WQI) and Pearson’s correlation coefficient (r) was determined using data of physicochemical parameters of lakes. Principal Component Analysis (PCA) performed using PAST3 software to identify the factors responsible for variations in water quality. Main Findings: The monitored forty lakes distributed across the three major watersheds namely Koramangala and Challaghatta valley, Vrishabhavathi valley and Hebbal valley were grouped under three different WQI status like good water quality (10%); poor water quality (37%) and very poor water quality (53%). Majority of these restored lakes has become polluted which indicates improper decontamination and poor maintenance of restored lakes. Application of this study: This study provides vital information for policymakers to understand the gaps which helps in the course correction while implementing further rejuvenation of lakes. Novelty/Originality of this study: The efficacy of rejuvenation was assessed through integrated cost-effective scientific approaches for the lake monitoring. Monitoring during the pre and post rejuvenation period has aided in assessing the efficacy of rejuvenation, which is done for the first time in India. Keywords: Lake rejuvenation, Water quality, Pollution, WQI, Multivariate analysis INTRODUCTION Lakes and water bodies also referred to as wetlands are one of the most productive ecosystems contributing to ecological sustainability thereby providing necessary linkages between land and water resources. The quality and hydrologic regime of these lakes and wetlands are directly dependent on the integrity of its watershed. Urban lakes have been aiding in recharging groundwater resources, microclimate moderation, floods mitigation, supported local livelihood (fish, fodder, etc.), local water (irrigation and domestic) demand apart from recreation facilities. Washing, household activities, vegetable cultivation and fishing are the regular activities in the lake for livelihood. In the last couple of decades, rapid urbanization coupled with unplanned anthropogenic activities has altered the wetland ecosystem severely across the globe. Changes in land use and land cover (LULC) in the wetland catchments influence the water yield and water quality of the lakes. Reduction of wetlands in Bengaluru and the pollution load has increased over years due to population growth, urbanization, industrialization, land use changes, encroachments, etc. (Ramachandra & Aithal, 2016). This has escalated greenhouse gas (GHG) footprint of about 19796.5 Gg of CO2 equivalents from various sectors in Bengaluru (Ramachandra & Shwetmala, 2012; Ramachandra et al., 2015a), with significant share from waste sector, domestic wastewater sector emits 759.29 Gg (15.42 and municipal solid waste emits 374.73Gg of CO2 equivalents (Ramachandra et al., 2015a). The sustained inflow of untreated wastewater has increased the pollution levels which is evident from the nutrient enrichment and consequent profuse growth of macrophytes, impairing the functional abilities of the wetlands. Reduced treatment capabilities of wetlands have led to the decline of native biodiversity. Apart from this, prevailing unhygienic conditions with mosquito menace and contamination of groundwater levels has been affecting the livelihood of wetland dependent population, which necessitated rejuvenation of lakes in Bengaluru. Lake restoration or rejuvenation endeavour is toward the recovery of lakes that has been degraded or damaged. Lake restoration is very important as the pollutants in lake can cause serious problem for human health and the environment. In Bengaluru, there are many para state agencies connected with the governance like BBMP (Bruhat Bengaluru Mahanagara Palike), BDA (Bengaluru Development Authority), BWSSB (Bengaluru Water Supply and Sewerage Board), PCB (Pollution Control Board) at Central and State Government and various departments including Revenue, Fisheries, Minor Irrigation, Forest, Ecology and Environment Department, Citizens, NGOs etc. Figure 1 illustrates the steps involved in lake rejuvenation and conservation.