Assessment of the Influence of Catchment Characteristics on Thermal Regimes of Tropical Reservoirs through Landsat 8 Satellite Imagery

Surface Water Temperature (SWT) is a key indicator for understanding ecological condition of inland water bodies and thermal dynamics, especially under increasing anthropogenic pressures and climatic variability. However, the scarcity of in situ observations in tropical regions poses challenges in analysing spatio-temporal thermal dynamics, primarily due to complex interactions among spatial, environmental, and localized factors. This study develops a remote sensing-based modeling framework to map and analyze SWT variations in two tropical reservoirs—Bhadra and Tungabhadra—within a same river basin in southern India. Despite their similar hydroclimatic conditions, the reservoirs exhibit distinct catchment characteristics. Using Landsat 8 thermal imagery from 2016 to 2021, the framework effectively spatial and temporal trends in SWT and examined the influence of potential factors of contributing catchment i.e., land use/land cover (LULC), rainfall, and air temperature using Google Earth Engine (GEE). The approach demonstrated robust performance (R² = 0.62; RMSE = 0.98), supporting its applicability in data-scarce regions. Thermal mapping revealed consistently higher SWT near inflow and periphery zones of the reservoirs adjacent to urban or agricultural land. Statistical analyses confirmed significant associations between elevated SWT and anthropogenically modified landscapes. These findings underscore the utility of medium-resolution satellite data for thermal monitoring and highlight the critical role of integrated catchment management in mitigating thermal stress in tropical reservoirs.