[Background]Plain reservoirs in arid regions face severe ineffective evaporation loss. Selecting efficient, environmentally friendly, and economically viable physical covering structures to reduce water surface evaporation is a key approach to achieving the sustainable utilization of water resources. [Methods]This study was conducted in Kunyu City, Hotan Prefecture, Xinjiang. A control experiment was established in large evaporation tanks with a diameter of 6 meters. Three types of physical covering materials—homogeneous floating balls, bottom-weighted floating balls, and hexagonal diamond-shaped floating bodies—were used to fully cover the water surface, with an uncovered blank group set as the control. Through long-term continuous monitoring, the evaporation inhibition efficiency of different covering structures under complex meteorological conditions and their impacts on the water environment were systematically evaluated. [Results]The findings revealed that: (1) The water surface evaporation process exhibited significant seasonal fluctuations, and the evaporation inhibition effect of the covering layer was comprehensively driven by meteorological factors; (2) The structural morphology of the covering units had a significant impact on water-saving efficiency. The hexagonal diamond-shaped floating bodies achieved an average evaporation inhibition rate of 75.2% at a coverage rate of 83%; while for the two types of floating balls with a coverage rate of 86%, the bottom-weighted floating balls (70.2%) outperformed the homogeneous floating balls (66.7%); (3) Water quality tests indicated that floating ball coverage did not cause secondary pollution to the water body, and the water quality indicators met the standards for agricultural irrigation. The long-term ecological effects of the hexagonal floating bodies require further quantification;(4) On the premise that the evaporation inhibition efficiency meets the engineering design indicators, the homogeneous floating ball water surface coverage scheme exhibits better economic feasibility and cost-effectiveness.[Conclusions]Different physical covering forms vary in water-saving benefits. In engineering practice, a multi-dimensional trade-off should be made based on water-saving rate, economy, and ecological security. The results of this study can provide theoretical basis and data support for the optimization of evaporation inhibition technologies and efficient water resource management in plain reservoirs of arid regions.