Water Quality Assessment of Harvested Rainwater Across China's Loess Plateau: Implications for Precision Irrigation

ABSTRACT Harvested rainwater is increasingly recognized for precision irrigation; however, emitter clogging from poor water quality remains a major obstacle. Specific factors driving clogging and the external influences are still unclear. To address this, 117 rainwater harvesting tanks on the Loess Plateau were surveyed. Water quality was evaluated using key physicochemical parameters, and clogging risk was assessed. The results showed that tank material, construction period and precipitation significantly influenced quality. For different materials, Na + , Ca 2+ , Mg 2+ and K + ranged from 0.29 to 1611.00, 0.62 to 130.50, 0.17 to 36.06 and 0.21 to 11.19 mg L −1 , respectively. Shorter construction periods were associated with lower Ca 2+ but higher K + and Na + . Moreover, ion concentrations—especially Na + —were elevated near the 300‐mm precipitation gradient. Although the Entropy Water Quality Index and United States Salinity Laboratory diagram indicated that approximately 86% of samples were suitable for irrigation, only approximately 2% met precision irrigation standards (pH, total hardness [TH], langelier saturation index [LSI], ryznar stability index [RSI], Fe and Mn). Notably, enhanced polyvinyl chloride (EPVC) tanks exhibited superior performance across all indicators. This study presents a framework for tank management, providing a reference for optimizing rainwater harvesting and advancing precision irrigation in the Loess Plateau and similar regions.