Abstarct: Evaporation from open water reservoirs is one of the major causes of water resource losses, particularly in arid and semi-arid regions. In this study, the performance of multi-segment floating polystyrene covers and the effects of element geometry and the perimeter length of the open spaces between them on the surface evaporation rate were experimentally investigated. For this purpose, floating covers with four identical opening geometries—circular, triangular, rhombic, and rectangular—were designed and tested to cover a basin with a surface area of 1.14 m² and a depth of 0.50 m, such that the total open area was kept constant at 0.415 m² while the perimeter lengths differed among configurations. The experimental results showed that multi-segment floating covers significantly reduce surface water evaporation; however, their efficiency is strongly influenced by the geometry of the elements and the extent of the open perimeter between them. The highest evaporation reduction was observed for circular covers, ranging from 48% to 75%, whereas rhombic, triangular, and rectangular covers exhibited evaporation reductions of 36%–71%, 46%–73%, and 33%–69%, respectively. The findings indicate that increasing the open perimeter length between elements and increasing wind speed reduce evaporation suppression efficiency by decreasing the thickness of the air boundary laxyer and enhancing heat and mass transfer. In addition, surface water flows played a significant role in limiting evaporation by reducing surface temperature. Furthermore, a nonlinear empirical model baxsed on net radiation was developed to predict the latent heat flux of evaporation. Model validation using both laboratory and field data demonstrated good agreement and acceptable accuracy between predicted and observed values. Overall, the results of this study indicate that optimal selection of the geometry of multi-segment floating covers can serve as an effective and low-cost approach for reducing evaporation from open water reservoirs.