Quantification and mapping of maize crop evapotranspiration using the surface energy balance algorithm for land model and medium-resolution satellite data

Evapotranspiration (ET) is a key variable in the hydrologic cycle that directly affects the redistribution of precipitation and surface balance. ET measurements with high temporal resolution are required for coupling with models of highly dynamic processes, e.g., hydrological and land surface processes. The Amaravathi River Basin is the focus of Tamil Nadu, as its major water resource for industry and major grain producing regions. However, this area is facing serious water resource shortages and water pollution problems. The present study used Landsat 8 satellite remote sensing data, in situ meteorological observations, and the surface energy balance algorithm for land (SEBAL) model with daily vegetative indices and energy fluxes in the River Basin. Moreover, factors influencing ET were also identified based on the results of this study. ET varies with land cover type and physical and chemical properties of the underlying surface. Furthermore, ET is also controlled by water availability, radiation, and other atmospheric weather factors conditions, whereas the CROPWAT model, based on the FAO 56 Penman-Monteith method, was employed to estimate seasonal water requirements and comparison was done with the SEBAL model. The root mean square error (RMSE) for ETa exhibited an RMSE of 0.65 mmd−1 and demonstrated an R2 exceeding 0.93. Finally, based upon crop cutting experiments (CCE), yield data and SEBAL-derived ET spatial water productivity maps were obtained by mathematical operations of the yield and ETa raster maps. The average maize yield of the study area was 7,567 kg ha−1, which was close to official agricultural marketing department data. The seasonal maize crop water requirement based upon SEBAL was 470 mm and that based upon CROPWAT was 506.3 mm, indicating that the SEBAL model shows good capability to detect CWR demand under study at the Amaravathi River basin scale. The average physical and economic maize water productivity was 1.61 kg m−3 and Rs. 40 m−3 across the Amaravathi River Basin, respectively. This study identifies high-performing and low-performing water productivity regions across the Amaravathi River Basin.