Estimation of actual evapotranspiration using surface energy balance algorithm for land in the lower Bhavani basin

Evapotranspiration is a vital process that substantially sustains the hydrothermal balance. The spatial and temporal distribution of evapotranspiration is critical for the management of water resources and drought monitoring at a regional scale. Surface Energy Balance Algorithm for Land (SEBAL) was employed to compute daily actual evapotranspiration in the lower Bhavani basin using Landsat 8 imagery, weather data and digital elevation model. The study aimed to analyze the spatial and temporal distribution of evapotranspiration. In addition, the influence of surface parameters such as surface albedo, land surface temperature, normalized difference vegetation index and net radiation flux on evapotranspiration was also investigated. The results revealed that SEBAL estimates agreed to 86.5 per cent with pan evaporation. Surface evapotranspiration showed seasonal variability with lower rates during winter and recorded maximum evapotranspiration during summer. Land use classes such as flooded vegetation and water bodies were found to have higher rates of mean daily evapotranspiration, whereas bare soil had lower evapotranspiration. Net radiation was noticed to have a significant impact on daily evapotranspiration among surface parameters. Hence, SEBAL can produce accurate evapotranspiration estimates for the study area. Moreover, vegetation cover and hydrothermal conditions significantly affect the surface parameters, which considerably affect surface evapotranspiration.