Mapping daily and seasonally evapotranspiration using remote sensing techniques over the Nile delta

The rapid escalation in water demands for agriculture, domestic, and industry sectors requires skillful management of this limited resource. Globally, the agriculture sector is considered the main user of the water resource. Actual evapotranspiration (ETc) is an important tool in determining the water requirements of different crops. Therefore, precise estimation of the ETc is the major parameter in the water balance of arid and semi-arid agriculture regions such as Egypt. Recently, both Remote Sensing and Geographical Information Systems (GIS) become the main techniques that can be efficiently used for estimating the ETc on regional and global coverage. The main goal of this study was to estimate the daily and seasonally ETc over the Nile delta using remote sensing techniques. These techniques were Surface Energy Balance for Land (SEBAL) algorithm with 24 Landsat 8 images. Additionally, FAO-Penman-Monteith method was used to validate the derived ETc from SEBAL algorithm under the same conditions using several performance criteria to assess the performance of the SEBAL algorithm with Landsat 8 in estimating the ETc over the Nile delta. The results revealed that the SEBAL algorithm with Landsat 8 images appears to provide an acceptable estimation of the spatial and temporal distributions of ETc over the Nile delta with acceptable accuracy with R-2 = 97.83%, RMSE about 0.469 mm/day and 15.9% NRMSE. The derived ETc from SEBAL algorithm was then used to estimate the water balance and the irrigation efficiency of the study area. Results of water balance estimates revealed that most of the seasonal ETc (93%) was originally met by surface water and groundwater supplies; however, the remaining portion (7%) was particularly met by precipitation. Furthermore, the estimated irrigation efficiency was about 48.6% in the central portion of the Nile delta. Overall, the performance of the derived ETc from SEBAL algorithm compared to available ground datasets demonstrates the potential of using the SEBAL algorithm with Landsat 8 images for water use and water balance estimates within the Nile delta.