Evaluating the impact of floating spheres on evaporation reduction and water salinity control in reservoirs

Abstract

The construction of simple reservoirs in arid regions helps meet the water demands for agricultural irrigation, industry, and domestic use, while also alleviating local water shortages and related issues. However, environmental concerns associated with reservoir development are becoming more evident. For instance, the stored water is gradually becoming saline. Studies suggest that reducing water evaporation over extended periods can effectively lower the salt concentration in the water. Currently, there is limited research on salt migration in reservoir water when covered with anti-evaporation materials. Given the potential impact of these materials on the water environment and hydrodynamic conditions, this study seeks to examine the spatiotemporal distribution patterns of reservoir mineralization under such covering. To this end, laboratory and field experiments were conducted to analyze the impact of covering the water surface with floating high-density polyethylene spheres to reduce evaporation and its effect on water salinity. These experiments included monitoring water temperature, dissolved oxygen, pH, sediment resuspension, and water conductivity, as well as calculating the contribution of sediment release and evapotranspiration to the increase in salinity concentration within the water column. This study investigates the role of floating high-density polyethylene (HDPE) spheres in reducing reservoir evaporation and mitigating water salinity. Laboratory and field experiments assessed the effects of different coverage levels (0 %-74.98 %) on evaporation rates, sediment resuspension, and water chemistry. The findings indicate that covering 74.98 % of the reservoir surface led to a 28.97 % reduction in salinity (p < 0.05) over one irrigation cycle. Evaporation inhibition varied from 13.56 % to 60.19 %, depending on coverage. However, floating spheres exhibited reduced effectiveness at high wind speeds (>10.7 m/s), highlighting the need for additional containment strategies. Future research should explore long-term durability, ecological impact, and cost-effectiveness of large-scale deployment.