Analysis of evaporation-induced water losses from rectangular and cylindrical rainwater harvesting basins (non-truncated and frustum) in a hot tropical climate (Burkina Faso)
- 2025 IEEE Multi-conference on Natural and Engineering Sciences for Sahel's Sustainable Development (MNE3SD) : 1-10
Résumé
This study models and simulates rainwater harvesting basins in the Sahelian zone to quantify evaporation-driven water losses and assess implications for design and water-resource management. Four basin geometries are evaluated—parallelepiped, prismoid (rectangular frustum), truncated cone (cylindrical frustum), and perfect cylinder—using a unified framework that combines (i) geometric characterization (including the free-surface area under side-slope constraints for truncated shapes) and (ii) a heat-balance thermal model to estimate water-surface temperature and evaporation losses in both mm/day and m3/day. Results show that the daily evolution of mean surface water temperature is nearly identical across geometries, and evaporation rates expressed per unit area remain comparable (about 2 to 9.7 mm/day), implying limited sensitivity of areal evaporation to basin shape under identical atmospheric forcing. In contrast, the consequences in terms of absolute water volume losses are substantial because geometry controls the exposed free-surface area: non-truncated designs (parallelepiped and perfect cylinder) exhibit the lowest evaporated volumes (0.12–1.081 m3/day), the prismoid produces intermediate losses (0.49–2.0 m3/day), and the truncated cone yields the highest losses (0.6–2.6 m3/day). These findings highlight that, although shape does not materially change evaporation rates, it strongly affects evaporation losses through surface exposure, making geometric design a practical lever to reduce water depletion. This is particularly consequential for Sahelian rainwater harvesting systems, where limiting daily volumetric losses can improve water availability during dry spells and enhance the reliability of smallholder and cooperative irrigation strategies.
Mots-clés
Rainwater harvesting, evaporation losses, hot tropical climate, basin geometry, Burkina Faso