To What ExtentDoes Atmospheric Water Harvesting InfluenceHumidity in the Climate and Environment?

Atmospheric water harvesting (AWH) captures gas-phase water vapor from the air, but the environmental impact of extraction has not yet been determined. Herein we apply a quantitative assessment to determine sustainable AWH operational capacity across micro-, meso-, and macroclimate scales, with relevance to desiccant and compressor systems. We quantified a mass balance model comparing starting relative humidity (RHstart) to post-AWH relative humidity (RHend) for arid, temperate, and tropical climates (25%, 50%, 75% RHstart) as a function of the volume of water harvested within different buffer volumes (BVs) [km3] of air. The influence of an AWH device harvesting 1 million gallons per day (MGD) over an area (1 × 1 km2) extending to the troposphere (10 km) results in a decrease in humidity from RHstart = 50% to RHend = 47.8%; the same harvest spread over a BV 25× larger (5 × 5 × 10 km3) decreases the humidity to only RHend = 49.9%. The magnitude of harvesting would need to increase by 4 orders of magnitude (>10,000 MGD) to completely remove the humidity (RHend = 0) in the larger BV. Our results are not meant to minimize the influence of moisture removal, especially on small spatial scales. We aim to set the framework for beginning a conversation on policy and ownership rights for atmospheric water reservoirs.