The Photovoltaic modules installed on the surface of the water are naturally cooled, reducing the loss of thermal power generation. Floating photovoltaic systems (FPVS) combine existing photovoltaic systems with a floating structure to generate clean energy. To meet the growing electricity demand, FPV systems will be integrated alongside existing dams to enhance existing power sources. The results indicate that the investment toward installing FPV systems over the dams' reservoirs leads to a significant improvement in the overall system reliability minimizes load curtailment, and could potentially add more flexibility to the operator to dispatch power generated by hydropower plants during peak demands. The execution of the Karun-4 FPV power plant with an annual production of 16758969 kWh of energy has reduced the water evaporation of the dam's reservoir water and after eight years and four months, the investment cost was returned and its nominal performance is 81.7 percent. Adding a floating solar power plant with 10% of the lake reservoir cover of six dams saves 70.7 million cubic meters of water per year. This amount of fresh water is enough to meet the annual needs of one million people.