Evaporation from free water surface is considered a very important constituent in both the energy and hydrologic cycles. Precise measurement of evaporation from the free water surface is almost impossible. This is why we need a calculation model for free water evaporation. In this study, a simple mass-transfer evaporation model was developed to be applicable over Lake Nasser in the hyper-arid region located in the south of Egypt. Measured meteorological data (2011–2014) at two stations, Aswan and Abu-Simbel, were used to calculate free water surface evaporation using Priestly–Taylor equation. Priestly–Taylor equation was used because it is the most appropriate equation for Lake Nasser evaporation according to the literature. Results from this model were used to develop a simple mass-transfer evaporation model. The statistical analysis for both calibration and validation periods were very good. The slope of the regression line is about 0.9, with a coefficient of determination of 0.98. The t value is 0.6, at p value of 0.544, which is much greater than 0.05. The developed model could be used with confidence at Aswan meteorological station or on the average of the two meteorological stations, while it should be used carefully on Abu-Simbel meteorological station.

从自由水表面蒸发被认为是能量和水文循环中非常重要的组成部分。从自由水表面精确测量蒸发几乎是不可能的。这就是为什么我们需要自由水蒸发的计算模型的原因。在这项研究中，开发了一种简单的传质蒸发模型，适用于位于埃及南部高干旱地区的纳赛尔湖。利用Priestly-Taylor方程，使用了阿斯旺（Aswan）和阿布辛贝（Abu-Simbel）这两个站点的实测气象数据（2011-2014年）来计算水面的自由蒸发量。使用Priestly–Taylor方程是因为根据文献，它是最适合纳赛尔湖蒸发的方程。该模型的结果用于建立简单的传质蒸发模型。校准期和验证期的统计分析都非常好。回归线的斜率约为0.9，确定系数为0.98。t值为0.6，在p值为0.544，远大于0.05。所开发的模型可以在阿斯旺气象站或两个气象站的平均值上放心使用，而在阿布辛布气象站则应谨慎使用。