Abstract

Purpose of the study: The undulating terrain of Bengaluru landscape (of 740 sq.km) facilitated the creation of many lakes / tanks in the past, for the traditional uses of irrigation, drinking, fishing and washing. This led to Bengaluru having 1452 water bodies through the centuries. 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. The city lacks adequate infrastructure for sanitation, leading to inappropriate management of the wastewater and sewage generated in the locality. Most of the sewage (domestic) and wastewater (industries) generated is discharged directly into storm water drains that ultimately link to water bodies. The sustained inflow of wastewater has led to the nutrient enrichment evident from algal bloom, poor water quality, etc. Pollution of surface water bodies led to the contamination of groundwater resources with the serious health consequences (water borne diseases) and 40% of Bengaluru depends on groundwater for domestic use. Local administration (BBMP: Bruhat Bengaluru Mahanaga Palike) initiated rejuvenation of these lakes in response to the demand from the stakeholders including local public. The main objective of the present work is to assess the efficacy of the restoration endeavour in Bengaluru lakes, Karnataka, India.

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: The present study on lakes in Bengaluru has underlined the main drivers that caused changes in water quality, elaborated gaps in restoration activities and solutions to be implemented which can help the decision makers in planning pollution abatement measures for wetland protection, conservation and management.

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. This provides vital information for policymakers to understand the gaps which helps in the course correction while implementing further rejuvenation of lakes.

Keywords: Lake rejuvenation, Water quality, Pollution, WQI, Multivariate analysis