Abstarct: Abstract In recent years, the growth of population and the development of communities has caused the reduction of fresh water resources in many regions of the world, especially in arid and semi-arid countries. If the necessary measures for management, proper use and reduction of water loss are not implemented, water shortage will become a big and serious threat to human life. If these measures become universal, they can make a significant contribution in preventing water loss. In arid and semi-arid regions, the main cause of water loss can be considered the phenomenon called surface evaporation, which occurs at temperatures lower than the boiling point of water. Therefore, it is an inevitable phenomenon and according to the location and weather conditions of the countries, it plays a role as an important factor in the loss of water resources in a country. One of the main methods to reduce evaporation from the surface of open tanks, which is used in many hot and dry regions, is the use of physical coatings. These covers prevent the direct contact of sunlight with the water surface and reduce the rate of evaporation. In this research, the rate of evaporation in the Kalpoosh dam has been estimated, taking into account the climate and weather conditions, etc., the rate of evaporation has been calculated using various methods, experimental formulas, and water balance measurements, and in the following, the most optimal method and The appropriate evaporation coefficient was chosen to estimate evaporation. According to the calculations, Ivanov's experimental method with the least amount of error has the best overlap with the amount of observed evaporation from the pan, and the appropriate coefficient of evaporation was examined from among the coefficients between 0.۶ and 0.۹, and the coefficient of 0.۸۵ was chosen with the least error. And then in the next rank, the experimental formula of the American Civil Engineering Organization was selected. Other methods cannot be used for the Kalpoosh dam due to the calculation of the lack of steam pressure in those formulas and the possibility of calculation errors with the actual value. In this research, evaporation reduction methods have been briefly discussed, and at the end, its effectiveness The methods have been investigated in the case of the Kalpoosh dam. The method of using wind breakers was introduced as an optimal and applicable method due to the topographical conditions and the effect of different temperature factors, as well as checking the amount of evaporation in different months of the year.