The climate change has directed impacts on hydrological process such as evaporation of water surface. Evaporation which is lost from agricultural water reservoirs can be potentially large and represents a significant portion of the total water managed for irrigation in arid or semi-arid climates. Floating covers are one of the methods to reduce evaporation from surface water reservoirs. In the first part of this research, several methods (Penman, Stephens–Stewart, Meyer, Henfer, Marciano, Shahtin, Tichomirov, Ivanov and USBR) were used to predict evaporation from meteorological data in open water reservoirs due to simplicity and low variation of meteorological data. Based on comparisons of RMSE, MBE and R 2 between methods and evaporation pan, the Stephens–Stewart method was selected as the best method. Ivanov and Tichomirov methods are at the second and third places, respectively. The preference of Stephens–Stewart method indicate the importance of temperature and solar radiation on evaporation of water surface in Isfahan. In the second part of this research, the probable impacts of climate change on evaporation in Isfahan were studied. To study the effects of climate change on water evaporation of water surface, a combination of various general circulation models (GCMs) under A 2 scenario was used through a weighting approach to generate different climate change patterns including the ideal, medium, and critical patterns. Meteorological data for 2020-2049 were produced using LARS-WG5.5 and climate change patterns. Then with the estimated parameters, evaporation of surface was compared with evaporation pan and evaporation baseline (1971-2000). The results show that the annual temperature of Isfahan would increase by 0.98- 1.58 degree and the solar radiation would increase by 2.69- 7.23 percent. The increased amounts of temperature and solar radiation can significantly impact the changes on evaporation of surface water. Annual evaporation would change 0.36 to 0.76 mm/day compared to the baseline. The maximum Annual evaporation would change 0.90 mm/day in critical Pattern compared to the evaporation pan. The aim of third section of this research was to characterize the influence of various floating covers (Polystyrene, Polystyrene with aluminum and polycarbonate) on the evaporation rate from several water reservoirs. The water level is measured in one year from October 2014 until November2015.The results of measured evaporation in form of a randomized complete block design with three replications (three types of coverage and an uncovered) were analyzed in SAS software and comparison of them at confidence level 99% (P 0.01) and Duncan test was conducted. The analysis of data show that there was significant effect on reducing evaporation from the covered reservoir. The maximum rate of evaporation from uncovered reservoir is 13.03 mm/day and Polystyrene, Polystyrene with aluminum and polycarbonate covers were 2.33, 2.87 and 3.06 in July, respectively. Results show that the Polystyrene, Polystyrene with aluminum and polycarbonate, can reduce amount of evaporation by 85.60, 83 and 76.49, respectively. These amounts represent a good performance of three covers in reducing evaporation from reservoirs. Polystyrene Cover indicate the better performance than the other covers to reduce evaporation of water surface. Keywords : Climate Change, Stephens- Stewart, Evaporation, GCMs, LARS-WG5.5, Polystyrene, polycarbonate