Research progress on the utilization technologies of agricultural non-conventional water resources

Against the backdrop of worsening global water scarcity, the development and utilization of unconventional water resources and the construction of diversified water supply systems have become key paths for countries to alleviate the contradiction between water supply and demand and promote sustainable agricultural development. Based on the statistical data of unconventional water resources over the past 20 years, this study first conducted a quantitative analysis of the current development status of unconventional water resource utilization in China. Then, it retrieved and analyzed the evolutionary trends of research in this field using the CNKI (China National Knowledge Infrastructure) and Web of Science databases; additionally, it systematically sorted out the utilization technologies, agricultural applications, and innovative practices of reclaimed water, rainwater, brackish water, and atmospheric water. The results showed that: The utilization volume of unconventional water resources in China has increased continuously over the past 20 years, reaching 25.16 billion m³ in 2024. In terms of spatial distribution, it presents the characteristics of "large total volume with concentrated distribution, more in the north and less in the south" the utilization of such resources in water-scarce northern regions, including the Haihe River Basin, Yellow River Basin, Beijing, and Tianjin, accounts for a prominent proportion. It is predicted that the available volume of agricultural unconventional water resources will reach 34.38 billion m³ by 2030, indicating significant development potential and broad application space for agricultural unconventional water resources; during 2000-2024, research in this field has shown a fluctuating growth trend, with themes focusing on reclaimed water irrigation, brackish water irrigation, and other directions. This research belongs to interdisciplinary and comprehensive studies, involving environmental science, agricultural engineering, agronomy, and other disciplines; research institutions are mainly universities in North China and Northwest China, and their layout responds to regional water scarcity demands. As the unconventional water resource with the largest utilization volume, reclaimed water needs to rely on the continuous innovation of membrane technology. It combines conventional treatment with advanced treatment, and is equipped with disinfection processes to achieve high reuse standards. Rainwater utilization focuses on the synergy between collection-storage and utilization, adopting composite and ecological rainwater harvesting to serve agriculture in arid regions, and matching with intelligent scheduling and new materials to improve management efficiency. Brackish water utilization centers on desalination, salt reduction, and crop stress mitigation, constructing a complete technical solution from pretreatment to advanced treatment. By integrating the strategies of mixed irrigation and alternate irrigation of brackish and fresh water, along with amendments and agronomic measures, it is suitable for the irrigation of salt-tolerant crops such as cotton and wolfberry. For atmospheric water harvesting, improving efficiency and reducing costs are the core; strengthening the combined surface water generation technology (an energy-efficient atmospheric water harvesting technology) can provide a new cost-effective water source path for agriculture in arid regions. In the future, through optimizing process combinations, reducing production costs, and strengthening regionally differentiated applications, the efficient development and scientific utilization of agricultural unconventional water resources will provide important support for sustainable agricultural development.