Reducing Evaporation in Arid & Desert Reservoirs
Why arid-climate reservoirs lose the most water to evaporation — and which suppression methods deliver the biggest savings in hot, dry, windy conditions.
Arid and desert reservoirs are where evaporation hurts most. Every one of the six drivers lines up against you: fierce solar radiation, very low humidity, high temperatures and frequent dry wind all push the vapour-pressure deficit — the engine of evaporation — to its highest. Open water in these climates can lose on the order of 2–3 metres of depth per year, and a recent analysis warns of a “water storage paradox”: expanding reservoir surface area to store more water can increase evaporative losses enough to offset much of the gain (Aminzadeh et al., 2025).
What works best here
Because the deficit is so large, high physical coverage wins. Continuous geomembrane covers and high-coverage modular floating covers reach the highest suppression by sealing the surface, and they also block sunlight to control algae. Shade balls are a lower-coverage but simpler option, and floating solar adds power generation while shading part of the surface — attractive where land and electricity are both scarce.
What to watch
Wind is the spoiler. It both accelerates evaporation (see the mass-transfer method) and disperses lightweight covers and chemical monolayers, so ballast and wind resistance matter as much as raw coverage. Intense UV also ages materials faster, making UV-stabilised products and long warranties worth the premium. Estimate your own site’s loss and the value at stake with the cost-benefit page before committing.