Evaluating evaporation rate from high Aswan Dam Reservoir using RS and GIS techniques

Abstract

Egypt is one of the countries facing challenges due to its limited water resources represented by its fixed share of the Nile water (55.5 BCM) according the 1959 agreement with Sudan. Lake Nasser is a man-made fresh water reservoir and its evaporation losses are an important contributing factor to the lake water budget. Although, no universally recognized method is known for evaporation estimation, reliable evaporation data are necessary for efficient management of the reservoir and the scare water resources. The aim of this research is calculating monthly evaporation rates using Remote Sensing (RS) and GIS techniques. The study applied Surface Energy Balance System (SEBS) method using Terra Moderate Resolution Imaging Spectroradiometer (MODIS) satellite earth observation data at years 2006 and 2012. Additionally, remote sensing ET product from the MODerate Resolution Imaging Spectrometer (MOD16) at years 2006, 2010 and 2012 were used to determine the monthly spatial distribution evaporation rates at Lake Nasser. The results were processed using ArcGIS software. Atmospheric parameters predicted from Weather Research and Forecasting (WRF) model were used also to estimate monthly evaporation rate using Harbeck equation which is typically used by High Aswan Dam Authority (HADA) responsible for the dam managment. The evaporation rates calculated from HADA data are compared with other methods (SEBS, MOD16 and WRF models). The average annual evaporation rate at year 2006 for HADA, SEBS and MOD16ET is 6.93, 6.38 and 6.61 mm/d respectively; the estimated by HADA is slightly higher than SEBS and MOD16 ET estimation. A high correlation was found between SEBS and MOD16 ET (R2 = 0.969 and P < .01), that gives a good indication of the use of only one method (SEBS) to estimate the evaporation, monthly evaporation rate.