Evaluating evaporation and seepage losses in lakes using sentinel images and the water balance equation

Abstract

The primary objective of this study is to assess changes in the water capacity of Aswan High Dam Lake (AHDL) due to evaporation and seepage losses. To achieve this, a comprehensive methodology was applied, incorporating Sentinel-3 imagery for surface area extraction using remote sensing techniques. By integrating water area calculations from satellite images, field data, and the lake’s water balance equation, monthly evaporation and seepage losses were estimated for 2021 and 2022. The results indicate that the average monthly evaporation losses for 2021 were approximately 1.41 billion cubic meters (Bm3), closely aligning with the Ministry of Water Resources and Irrigation (MWRI) estimates of 1.37 Bm3, representing a slight overestimation of 2.92% by the water balance method. Similarly, the average monthly seepage losses for 2022 were estimated at 0.005 Bm3, compared to MWRI’s reported 0.0046 Bm3, reflecting an overestimation of 8.70%. Additionally, the study found that the average monthly evaporation rate within AHDL was 210.88 mm/month, closely matching the Aswan High Dam Authority’s (AHDA) computed value of approximately 204.9 mm/month. These findings demonstrate that the water balance method, when integrated with remote sensing and field data, serves as a reliable tool for estimating monthly evaporation and seepage losses, as well as evaporation rates in AHDL.