Utilizing Satellite Imagery to Map Lake Surface Temperature and Explore its Effect on Evaporation Rate

This study aims to map the Lake Surface Water Temperature (LSWT) for the northern part of Aswan High Dam Lake (AHDL) within the years 2018, 2019, and 2020; and detect the effect of the estimated LSWT on the evaporation rate. To achieve these objectives, firstly, the LSWT maps were created from the Landsat-8 satellite images, a widely and conventional used method. Moreover, the LSWT maps were also generated by Sentinel-3 Sea and Land Surface Temperature Radiometer (Sentinel-3/SLSTR) satellite images. The created temperature maps by Landsat-8 were used to assess the ones produced by Sentinel-3. Then the relationship between the Sentinel-3 derived LSWT and the estimated evaporation rate, provided by floating hydro-meteorological stations within AHDL and reported by annual reports of the Ministry of Water Resources and Irrigation (MWRI), was determined. After assessing, it was found that the convergence percentage between the estimated temperature values by the Sentinel-3 and those estimated by Landsat-8 (the reference values) ranges from 1.00% to 4.71%, which indicates that the estimated temperature values from both satellite images are very close. Therefore, it is possible to rely on the results of the created temperature maps for the study area by Sentinel-3. Additionally, the study revealed a direct relationship between the evaporation rate and the LSWT estimated by Sentinel-3 within the same year. However, the results demonstrated that changes in the evaporation rate vary from year to year, indicating that LSWT is not the sole factor influencing.