Cutting Evaporation in Semi-Arid Climates
Semi-arid reservoirs face high seasonal evaporation. Which methods balance strong savings against cost when conditions are dry but not extreme.
Semi-arid reservoirs sit between temperate and desert extremes: a strong dry season drives high evaporation for much of the year, but more seasonal humidity and rainfall make conditions less punishing than a true desert. Annual loss commonly runs 1,500–2,200 mm, concentrated in the hot, dry months.
What works best here
The seasonality is an opportunity. High-coverage modular floating covers and shade balls deliver strong year-round savings, while floating solar is especially compelling where irradiance is high — generating power and cutting evaporation, with documented water-quality benefits in semi-arid conditions (Abdelal, 2021). Storage management — consolidating water into deeper, smaller-footprint storage during the dry season — reduces the exposed surface area that drives loss.
What to watch
Because conditions are less extreme than the desert, the cost-benefit calculus is tighter — the right method is the one whose savings clear its cost at your water value. Use Penman-Monteith or the mass-transfer method to estimate seasonal loss, and the cost-benefit page to size the payback before choosing.