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Item type:Publication, Access status: without files , The impact of cover geometry on evaporation suppression of partially covered water reservoirs(Elsevier, 2025-08-18); ; ; 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.Publicationtype: Journal Article52 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A novel method for assessing evaporation in small water bodies: considering floating covers, water surface flows, and wind speeds(Springer, 2025-04-04); ; ; In small water reservoirs, the effectiveness of floating covers on evaporation reduction, especially with water surface flows and wind, remains uncertain, and a reliable theoretical framework for estimating evaporation in these conditions is lacking. This study seeks to fill this knowledge gap through modeling and experiments. The research setup includes a small water basin (1.14m2 surface area, 0.5m depth) for water storage, a pump to make water surface flows (2.5–11lmin-1), two fans to create wind speeds (0–2.2ms-1) aligned with the water surface flows, black and white floating balls to cover 75% of the water surface, and various measuring instruments (e.g., thermometer, heat flux sensor). The findings reveal that due to the thermal mixing of the layers, water surface flows reduce evaporation to a specific flow rate, maintaining this reduction until a certain wind speed (1.4ms-1). Beyond this threshold, the evaporation reduction flow rate starts to retreat so that it reaches its lowest value at a wind speed of 1.8ms-1. Further escalation in wind speed negates the reduction in evaporation, leading to increased evaporation rates across all water surface flows. The study highlights the significant role of floating covers in reducing evaporation, showing 55–66% efficacy under various water surface flows and wind speeds. A mathematical relationship is developed using dimensionless numbers and non-linear regression analysis to enhance the applicability of laboratory findings for estimating evaporation in real conditions, showing a good agreement with measurements in a small agricultural reservoir.Publicationtype: Journal Article10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A novel framework for estimating the Bowen ratio over small water bodies(2025-02-02); ; ; The Bowen ratio, defined as the ratio of sensible to latent heat flux, is crucial for quantifying land-atmosphere energy exchanges and evaporation rates from terrestrial surfaces. Despite extensive research on the Bowen ratio over placid water surfaces (e.g., lakes), further investigation is needed to understand its dynamics in small reservoirs subjected to water inflow/outflow (i.e., surface flows) and wind. To address this knowledge gap, the evaporation rate and the sensible heat exchanges are measured between the water surface and overlying air in a small laboratory basin under different water surface flow rates (1.0–10.5 l min−1) and wind speeds (0–2.0 m s−1). Three different wind flow conditions are explored: no wind, headwind (opposing the water surface flow), and tailwind (aligning with water surface flow). The findings indicate strong correlations between sensible heat flux, water surface flow rate, and wind speed, particularly under headwind conditions. Nevertheless, concerning the latent heat flux, the measurements demonstrate that for each wind condition, the evaporation reaches its minimum value in a certain water surface flow rate, resulting in the highest value of the Bowen ratio. To facilitate the application of these laboratory findings for estimating the Bowen ratio under real environmental conditions, mathematical relationships using dimensionless numbers obtained through non-linear regression analysis are established. The results exhibit a good agreement with measurements in a small water basin.Publicationtype: Journal Article16 23