Evaporation Control

Evaporation control reduces the loss of liquid water to the air. Water evaporates from pond surfaces, exposed soil, and other wet areas, especially when conditions are warm, dry, and windy. In permaculture design, this function helps keep a limited water supply useful for longer.

Several factors influence the rate of loss. Sunlight supplies energy, moving air carries water vapor away, and a large exposed surface creates more opportunity for evaporation. This is why two stores holding a similar volume of water can lose different amounts if one is shallow and broad while the other has less exposed surface.

On soil, mulch can shade the surface and interrupt air movement immediately above it. Living ground cover also protects the surface, but its roots use water and its leaves release water through transpiration. The combined effect depends on the vegetation, weather, and the crops sharing the area. Reduced bare-soil evaporation does not automatically mean reduced total water use.

For tanks, a suitable cover can limit exposure while also helping protect water quality. For ponds, the design needs to balance water conservation with oxygen exchange, habitat, access, and maintenance. Completely covering a living pond is a different proposition from covering a storage tank.

Consider a young orchard where irrigation wets a limited root area beneath an appropriate mulch. Less water may be exposed at the soil surface than in a large, repeatedly wetted bare area. The irrigation pattern and surface protection work together.

Beginners can start by locating the places where water remains unnecessarily exposed after collection or application. Also distinguish evaporation from leakage, seepage, and plant use before choosing a remedy. Evaporation control connects with water storage, irrigation, shade, ground cover, and windbreaks. Its value lies in conserving water through measures suited to the particular storage or growing system, while preserving the other functions that water supports.