Aquatic weeds management and estimation of water losses from evapotranspiration must be taken into consideration in order to reduce water losses. The objective of this research is estimating the water losses through evapotranspiration of aquatic weeds in the Rosetta Branch in order to identify the quantities of water that could be saved when applying appropriate maintenance programs for aquatic weeds. To achieve the objective of this research, the research team identify areas of infection of the aquatic weeds using field visits, determine its coordinates using GPS and Satellite imagery (Landsat-8) and estimate of water losses through evapotranspiration of aquatic weeds by using the following evapotranspiration equation: ETc = ETo × Kc. The result for estimation of the average annual water losses through evapotranspiration of aquatic weeds in the Rosetta Branch during one year (from December 2015 to November 2016) were 21.3 million m 3 /year, 0.7 million m 3 /year and 1.1 million m 3 /year for water hyacinth, Common Reed and Torpedo grass, respectively.