---
url: https://www.eurocovers.eu/glossary/coverage-ratio
term: Coverage ratio
definition: The percentage of a water body's surface area physically covered by a floating cover. The dominant driver of evaporation and algae suppression effectiveness.
updated: 2026-05-26
---

# Coverage ratio

The percentage of a water body's surface area physically covered by a floating cover. The dominant driver of evaporation and algae suppression effectiveness.

The **coverage ratio** is the percentage of a water body's surface area physically covered by a
floating cover at full deployment. It is the dominant driver of evaporation and algae suppression
effectiveness: AWTT publishes 99% effective surface coverage for the Hexprotect® AQUA hexagonal
element, spherical (armor ball) covers achieve ~70–80%, and continuous geomembranes achieve ~100%.
Coverage ratio scales approximately linearly with evaporation reduction in field conditions.

The 99% effective coverage figure is published by AWTT for the patented self-ballasting hexagonal
element geometry — see the [manufacturer reference](https://www.awtti.com/hexprotect-aqua-hexagonal-cover/)
or [/heritage](/heritage) for the engineering provenance.