This thesis is intended to study the Techno-economic feasibility analysis of integrating WindrnPower Pumped Hydro-Storage system to the existing Hydroelectric Power plants in Ethiopiarnspecially to enhance the volume and efficiency of the Koka Hydropower Plant StationrnReservoir by pumping water from the lower reservoir to the upper reservoir in order to supplyrnreliable and steady water to the turbine. In the analysis five tasks are carried out these are: therncritical months that are mainly affected by evaporation and climate change are verified whichrnare March, April, May, June and July, the amount of the water that evaporates from thernreservoir per hour is determined by using the Evapo-transpiration calculation techniquernwhich is the Penman-Monteith equation with heat storage and it is a method with strongrnlikelihood of correctly predicting ETO in a wide range of locations and climates, by using thisrnmethod the average hourly evaporation for these five critical months becomes 24,112m3/hr,rnthe cost of a pipeline and the various components that contribute to the economics ofrnpipelines for the study area is carried out including designing a fluid distribution systemrnwhich is sizing of pipes and ducts, determination of the pressure drop in the system, and thernpower needed to pump required water to the upper reservoir, Wind energy and turbinerninvestment cost analysis using RETScreen Software, and the economic analysis which is seenrnfrom three different perspectives that are: the integration of wind power pumped hydrosystemrnfrom the point view of energy security of the Koka Hydropower Plant, thernprofitability of the wind power used for pumping purpose from the hydroelectric power or therngrid power pumping system, and the profitability of wind power used for pumping purposernfrom the diesel generator power pumping system.rnFinally from the point view of energy security of the existing Hydropower plants in Ethiopiarnthe integration of the wind power pumped hydro-storage system is the best solution.rnKey Words: RETScreen Software, Evapotranspiration, Pumped Hydro-storage, WaterrnTemperature