Exploring the cooling benefits of Urban Lakes: A multi-year analysis of Dhaka, Bangladesh

The historical and contemporary development of Dhaka city is predominantly unplanned, resulting in significant environmental deterioration. The lack of green and blue spaces and the built areas make it hard for people to stay in comfortable living conditions. The impacts of urban water bodies on the local thermal environment are examined in this study. Landsat 5, 7, and 8 images of 1991, 1996, 2001, 2006, 2011, 2016, and 2021 years were analyzed using ArcGIS (V.10.8) to look at the seasonal changes of normalized difference vegetation index (NDVI) and land surface temperature (LST) of the surrounding lake area. The LST was obtained at a spatial resolution of 30 m using Landsat TM and TIRS imagery, particularly in cloud-free conditions within the study area. The lake water controls the temperature of the adjacent area within 100 to 150 m. The presence of the lake mitigated the disparity between the maximum and minimum temperatures in the hinterland thermal conditions. With time, there was a gradual but consistent rise in temperatures across the board, encompassing the monthly peaks, lows, and averages. Notably, the highest temperatures increased at a faster rate compared to lower and average temperature ranges. It's important to highlight that the rate of temperature rise was more pronounced at 200 m from the lake compared to the increase observed at 100 m. The rise in global temperature due to climate change has made cooling effects less effective for blue bodies in cities. This study's outcomes will help urban planners understand the blue and green space planning in cities to create a comfortable living environment.