Water Harvesting and Utilization in the Earth–atmosphere–biological System: From Natural Processes to Technological Innovations

Abstract

Water is indispensable for municipal, domestic, and agricultural uses, yet its acute shortage disrupts nearly all aspects of human life across the globe. Water naturally exists in three phases—gas, liquid, and solid—which shift through changes in temperature and pressure. It is present throughout the Earth system, including the atmosphere, cryosphere, soil, and all living organisms. However, the demands for freshwater continues to rise while its availability declines due to population growth, rural–urban migration, and human-induced greenhouse gas emissions. Consequently, enhancing the potential for water harvesting has become critical for sustaining human wellbeing. This paper examines the potential for harvesting and utilizing water across different components of the Earth–atmosphere–biological system. Water harvesting from solid (ice) and liquid (rain) sources—across atmospheric, surface, and subsurface domains—has been practiced since ancient times to secure freshwater. Advances in science and engineering have improved the precision and efficiency of these methods, yet extracting water directly from atmospheric vapor remains a major technological challenge. Atmospheric water harvesting is emerging as a promising solution for addressing water scarcity in arid and inland regions that lack reliable liquid water resources. Cloud seeding technology with some chemicals like silver iodide, potassium iodide, sodium chloride, dry ice (solid CO2) etc can be used as cloud harvester to make artificial rain while sorption-based specialized materials like MOFs, hydrogels, and zeolites are used to absorb water vapor from the air, even in arid conditions. These sorbents capture liquid water molecules through mechanisms like hydrogen bonding. Once saturated, the material releases the water for collection. In water-scarce regions where fog and dew are abundant, atmospheric water present as vapour can serve as a valuable freshwater source when appropriate harvesting techniques are applied. Fog nets or mesh barriers placed perpendicular to wind flow can condense fog into liquid water, while spider webs and similar structures naturally harvest dew droplets. Technological advancements are expected to substantially enhance these water-harvesting processes, helping to meet future freshwater demands for humanity.