The impact of cover geometry on evaporation suppression of partially covered water reservoirs

Suppressing evaporative losses from water reservoirs has long been a challenge. While various methods have been developed to reduce evaporation, physical covers, such as floating elements, offer an efficient measure for reducing evaporative losses from open water storages. Although the impact of floating covers on evaporation reduction is well-studied, the influence of cover geometry and associated opening attributes at the surface remains underexplored. This study investigates the effect of different cover geometries with identical surface coverage fraction on the evaporation suppression efficiency of partially covered reservoirs. The results show that openings with larger perimeters lead to higher evaporation rates and lower suppression efficiency. Rectangular, diamond, triangular, and circular opening geometries resulted in 33–69 %, 36–71 %, 46–73 %, and 48–75 % reduction in evaporation, respectively, under various surface flow and air boundary conditions. We observed that water surface flow and wind speed initially promote thermal mixing and reduce evaporation, but beyond a threshold, the increased heat transfer dominates, causing the evaporation rate to rise. To bridge laboratory findings with real-world environmental conditions, a mathematical model is developed using dimensionless analysis and nonlinear regression. The model shows good agreements with field measurements obtained from small reservoirs.

Subjects

Evaporation suppression

Floating covers

Non-linear regression analysis

Opening geometry

Water reservoirs

DDC Class

551: Geology, Hydrology Meteorology

Options

The impact of cover geometry on evaporation suppression of partially covered water reservoirs