Effect of Winter Cloud Seeding on Downstream Water Quality: Spatial Comparison of Bukcheon and Odaecheon-1

To evaluate the potential impacts of winter cloud seeding on downstream water quality, this study compared long-term water quality data from two mountain streams in Gangwon Province, Korea: Odaecheon-1, located downstream of the Cloud Physics Observation Center (CPOS) and within the expected influence zone of seeding materials, and Bukcheon, situated outside the seeding impact zone. Monthly data from March, collected between 1997 and 2024, were analyzed for four key parameters sensitive to physical and chemical changes induced by artificial snowfall: water temperature, dissolved oxygen (DO), pH, and electrical conductivity (EC). Statistical analyses, including linear regression, revealed significant increases in water temperature (+0.147 ℃/yr, p = 0.005) and EC (+5.70 μS/cm/yr, p < 0.001) at Odaecheon-1, while Bukcheon showed either weaker or non-significant trends. Additionally, DO at Odaecheon-1 displayed a significant decreasing trend (-0.113 mg/L/yr, p = 0.005), suggesting potential biological or chemical responses to thermal and ionic changes. In contrast, pH remained stable at both sites over the 28-year period. This spatial comparison provides indirect yet compelling evidence that wintertime cloud seeding may alter downstream water quality through the influx of seeding materials and associated snowmelt processes. The findings support the need for continued monitoring and expanded investigations incorporating nutrient and organic matter indicators to better understand the broader environmental implications of weather modification practices.