Mr. Pranadh M will present his APS as per the details:
Date: 29th September 2025 (Monday)
Time: 1140 - 1315 hrs.
Venue: C-TARA Conference Room No. 1
Title: Evolution of lakes from rural to urban system and impacts on lake hydrology, ecosystem services and people- a case study of Bengaluru lakes
Guide: Prof. Pennan Chinnasamy
RPC Members: Prof. Haripriya Gundimeda, Prof. Chaaruchandra Korde
Abstract:
The interconnected lake systems in Bengaluru, India, face significant stress due to rapid, unplanned urbanization over the past three decades. Conventional individual lake-centric research approaches are constrained in addressing these concerns, asthe impacts cascade across interconnected lake systems. To overcome this, the present study adopts a lake series approach to assess the cascaded impact of urbanisation on highly degraded Yele Mallappa Shetty Lake series (YMSLS) in Bengaluru. Land use and land cover (1993–2023) analysis using remote sensing data shows built-up area in the YMSLS catchment rose from 7.2% to 34.6%, indicating significant urbanisation. This transformation has accelerated inflows of domestic, industrial, and commercial wastewater, producing severe and spatially uneven pollution loads. Downstream lakes within the series accumulate pollutants and show greater deterioration during summer. In this stage of the study, water quality assessment is extended beyond the watershed to the downstream river, which receives pollution from the YMSLS catchment via lake overflows and diversions. Results show that partially treated wastewater increases streamflow during the dry season, with a Sen’s slope of 2.04 m³/s per year (p < 0.01), but with compromised quality. Water quality indices confirm severe degradation: 89% of samples using Modified Water Quality Index (MWQI) fall in the ‘Poor to Unsuitable’ category, while the Overall Index of Pollution (OIP) shows 85% of samples as ‘slightly to heavily polluted’. However, it is identified that the urbanised catchment serves two essential functions. First, in terms of thermal regulation, Landsat-derived land surface temperature (LST) analysis shows overall warming and hotspot intensification in the catchment, while lakes persist as statistically significant cold spots. Application of the First Turning Point method reveals that perennial lakes, sustained largely by partially treated wastewater inflows, exert a cooling influence extending ~ 200 metres from their shoreline with an intensity of ~5 °C, stronger in summer than winter. Their cooling efficiency, defined as the ratio of cooling footprint to lake area, is exceeds two, showing the effect extends over more than twice the lake surface. Secondly, the diversion of treated wastewater (TWW) generated from YMSLS catchment, to upstream areas through HN Valley scheme and lake refilling project has promoted shallow aquifer revival. Trend analysis using the Mann–Kendall test and Sen’s slope estimator shows an average rise of 1.1 m per month (p < 0.01) in borewells within ~3 km radius of refilled lakes, with water quality within permissible limits. The results highlight the dual role of wastewater in an urbanising lake catchment. Partially treated discharges and water diversion to keep lakes clean, degrade downstream water quality through externalisation of pollution load. On the other hand, managed diversion, storage and reuse can create new ecological functions like cool islands and promote aquifer recharge. Collectively, cascaded impacts, extending to both upstream and downstream areas, reinforce the need for hydrological-scale planning to integrate lake networks into effective urban resilience strategies